CHAPTER 9 Electronic Suspension Systems OBJECTIVES After studying

CHAPTER 9 Electronic Suspension Systems

OBJECTIVES After studying Chapter 9, the reader will be able to: 1. 2. 3. 4. 5. Prepare for ASE Suspension and Steering (A 4) certification test content area “B” (Suspension System Diagnosis and Repair). Describe how suspension height sensors function. Explain the use of the various sensors used for electronic suspension control. Discuss the steering wheel position sensor. Explain how solenoids and actuators are used to control the suspension. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 2 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

KEY TERMS • • • • • Actuator Air suspension Armature AS Automatic level control (ALC) CCVRTMR Computer command ride (CCR) Desiccant Driver selector switch EBCM ECU Electromagnet Handwheel position sensor Height sensor Input Lateral accelerometer sensor LED Magneto-rheological (MR) Mode select switch Motor Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman • • • • • 3 MRRTD Output Perform ride mode Photocell Phototransistor Pulse width Pulse-width modulation Real-time dampening (RTD) RPO RSS Selectable ride (SR) Solenoid controlled damper Stabilitrak Steering wheel position sensor Touring ride mode Vehicle stability enhancement system (VSES) VS sensor Yaw rate sensor Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

THE NEED FOR ELECTRONIC SUSPENSIONS • • • Since the mid-1980 s, many vehicle manufacturers have been introducing models with electronic suspension controls that provide a variable shock stiffness or spring rate. The main advantage of electronic controls is that the suspension can react to different conditions. The system provides a firm suspension feel for fast cornering and quick acceleration and braking, with a soft ride for cruising. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 4 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

THE NEED FOR ELECTRONIC SUSPENSIONS FIGURE 9– 1 An electronically controlled suspension system can help reduce body roll and other reactions better than most conventional suspension systems. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 5 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS • • Sensors and switches provide input to the electronic control module (ECM), or system computer. The ECM, which may also be referred to as the electronic control unit (ECU), is a small computer that receives input in the form of electrical signals from the sensors and switches and provides output electrical signals to the system actuators. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 6 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS FIGURE 9– 2 Input devices monitor conditions and provide information to the electronic control module, which processes the information and operates the actuators to control the movement of the suspension. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 7 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS HEIGHT SENSORS • • Sensors, which are the input devices that transmit signals to the ECM, monitor operating conditions and component functions. A height sensor senses the vertical relationship between the suspension component and the body. Its signal indicates to the ECM how high the frame or body is, or how compressed the suspension is. A number of sensor designs are used to determine ride height, including a photocell type of sensor. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 8 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS HEIGHT SENSORS FIGURE 9– 3 A typical electronic suspension height sensor, which bolts to the body and connects to the lower control arm through a control link and lever. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 9 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS HEIGHT SENSORS FIGURE 9– 4 When suspension action moves the lever, it rotates the slotted disc and varies how much of the photo transistor is exposed to the LEDs, which vary the input signal. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 10 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS GENERAL MOTORS ELECTRONIC SUSPENSION SENSORS • • There are five different sensors found on electronic suspension systems, and GM vehicles can have between one and four of these sensors, depending on the system. Depending on the vehicle, the suspension position sensor may be called by a different name. It can be called: • • An automatic level control sensor An electronic suspension position sensor An air suspension sensor Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 11 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS GENERAL MOTORS ELECTRONIC SUSPENSION SENSORS FIGURE 9– 5 Typical suspension position sensor. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 12 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS GENERAL MOTORS ELECTRONIC SUSPENSION SENSORS FIGURE 9– 6 A three-wire suspension position sensor schematic. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 13 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS GENERAL MOTORS ELECTRONIC SUSPENSION SENSORS FIGURE 9– 7 A suspension height sensor. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 14 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS STEERING WHEEL POSITION SENSOR • • • Depending on the vehicle, the steering wheel position sensor may also be called a handwheel position sensor. The function of this sensor is to provide the control module with signals relating to steering wheel position, the speed and direction of handwheel position. The sensor is found on most real-time dampening (RTD) and road-sensing suspension (RSS) applications. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 15 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS STEERING WHEEL POSITION SENSOR FIGURE 9– 8 The steering wheel position (handwheel position) sensor wiring schematic and how the signal varies with the direction that the steering wheel is turned. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 16 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS STEERING WHEEL POSITION SENSOR FIGURE 9– 9 The handwheel position sensor is located at the base of the steering column. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 17 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS STEERING WHEEL POSITION SENSOR FIGURE 9– 10 Steering wheel (handwheel) position sensor schematic. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 18 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS VEHICLE SPEED SENSOR • • • The vehicle speed (VS) sensor is used by the EBCM to help control the suspension system. The vehicle speed sensor is a magnetic sensor and generates an analog signal whose frequency increases as the speed increases. The ride is made firmer at high speeds and during braking and acceleration and less firm at cruise speeds. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman FIGURE 9– 11 The VS sensor information is transmitted to the EBCM by Class 2 serial data. 19 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS PRESSURE SENSOR • • A pressure transducer (sensor) is typically mounted on the compressor assembly. This sensor is typically found on suspension systems that use a compressor assembly. The main function of the pressure sensor is to provide feedback to the suspension control module about the operation of the compressor. The sensor assures both that a minimum air pressure is maintained in the system and that a maximum value is not exceeded. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 20 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS PRESSURE SENSOR FIGURE 9– 12 An air pressure sensor. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 21 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS LATERAL ACCELEROMETER SENSOR • • • The function of the lateral accelerometer sensor is to provide the suspension control module with feedback regarding vehicle cornering forces. This type of sensor is also called a G-sensor, with the letter “G” representing the force of gravity. For example, when a vehicle enters a turn, the sensor provides information as to how hard the vehicle is cornering. This information is processed by the suspension control module to provide appropriate damping on the inboard and outboard dampers during cornering events. The lateral accelerometer sensor is found on the more complex suspensions systems, such as RTD and RSS systems that incorporate the vehicle stability enhancement system (VSES). Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 22 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS LATERAL ACCELEROMETER SENSOR FIGURE 9– 13 A schematic showing the lateral acceleration sensor and the EBCM. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 23 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

Quick and Easy “G” Sensor Test • Most factory scan tools will display the value of sensors, including the lateral accelerometer sensor (G -sensor). However, the G-sensor value will read zero unless the vehicle is cornering. A quick and easy test of the sensor is to simply unbolt the sensor and rotate it 90 degrees with the key on engine off. Now the sensor is measuring the force of gravity and should display 1. 0 G on the scan tool. If the sensor does not read close to 1. 0 G or reads zero all of the time, the sensor or the wiring is defective. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 24 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

Quick and Easy “G” Sensor Test FIGURE 9– 14 The lateral accelerometer sensor (G-sensor) is usually located under the center console. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 25 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS YAW RATE SENSOR • • • The yaw rate sensor provides information to the suspension control module and the EBCM. This information is used to determine how far the vehicle has deviated from the driver’s intended direction. The yaw sensor is used on vehicles equipped with Electronic Stability Control (ESC). Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 26 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS YAW RATE SENSOR FIGURE 9– 15 Yaw rate sensor showing the typical location and schematic. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 27 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION CONTROLS AND SENSORS DRIVER SELECTOR SWITCH • • The driver selector switch is a two- or three-mode switch, usually located in the center console, and is an input to the suspension control module. The switch that is used to select either touring (soft) or performance (firm) ride is found on the Selectable Ride (SR) and the Computer Command Ride (CCR) systems. The mode select switch status is generally displayed on a scan tool. The three-position switch is used on the Corvette RTD system, and allows the driver to select three modes of operation: • • • Tour Sport Performance Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 28 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION SYSTEM ACTUATORS • • • Each actuator in an electronically controlled suspension system receives output signals from the ECM and responds to these signals, or commands, by performing a mechanical action. Actuators are usually inductive devices that operate using an electromagnetic field. A simple electromagnet consists of a soft iron core with a coil of wire, usually copper, wrapped around it. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 29 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION SYSTEM ACTUATORS FIGURE 9– 16 A magnetic field is created whenever an electrical current flows through a coil of wire wrapped around an iron core. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 30 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION SYSTEM ACTUATORS FIGURE 9– 17 When magnets are near each other, like poles repel and opposite poles attract. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 31 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION SYSTEM ACTUATORS SOLENOIDS • • In a solenoid, the core of the electromagnet also acts as a plunger to open and close a passage or to move a linkage. Solenoids are cylindrically shaped with a metal plate at one end and open at the other end to allow the plunger to move in and out. The electromagnetic coils are placed along the sides of the cylinder. A preload spring forces the plunger toward one end of the device when the solenoid is de-energized, or there is no current in the coil. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 32 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION SYSTEM ACTUATORS SOLENOIDS FIGURE 9– 18 When electrical current magnetizes the plunger in a solenoid, the magnetic field moves the plunger against spring force. With no current, the spring pushes the plunger back to its original position. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 33 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION SYSTEM ACTUATORS SOLENOIDS FIGURE 9– 19 This air supply solenoid blocks pressurized air from the air spring valves when off. The plunger pulls upward to allow airflow to the air spring valves when the solenoid is energized. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 34 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION SYSTEM ACTUATORS ACTUATOR MOTORS • • If a current-carrying conductor is placed in a magnetic field, it tends to move from the stronger field area to the weaker field area. A motor uses this principle to convert electrical energy into mechanical movement. Electrical current is directed through the field coils on the motor frame to create a magnetic field within the frame. By applying an electrical current to the armature, which is inside the motor frame, the armature rotates from a strong field area to a weaker field area. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 35 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION SYSTEM ACTUATORS ACTUATOR MOTORS FIGURE 9– 20 An actuator motor uses a permanent magnet and four stator coils to drive the air spring control rod. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 36 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

ELECTRONIC SUSPENSION SYSTEM ACTUATORS ACTUATOR MOTORS FIGURE 9– 21 The stator coils of the actuator are energized in three ways to provide soft, medium, or firm ride from the air springs and shock absorbers. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 37 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION • The types of electronic suspension systems used on General Motors vehicles, as examples, include: • • Selectable Ride Automatic Level Control Air Suspension Computer Command Ride Real-Time Dampening/Road-Sensing Suspension Vehicle Stability Enhancement System Magneto-Rheological Suspension (F 55) Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 38 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 22 Selectable Ride as used on Chevrolet and GMC pickup trucks. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 39 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 23 ALC maintains the same ride height either loaded or unloaded by increasing or decreasing the air pressure in the rear air shocks. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 40 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 24 A typical schematic showing the air suspension compressor assembly and sensor. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 41 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 25 The typical variable-rate air spring system uses three height sensors, two in the front and one in the rear, to monitor trim height and to provide input signals to the ECM. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 42 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 26 The air spring compressor assembly is usually mounted on rubber cushions to help isolate it from the body of the vehicle. All of the air entering or leaving the air springs flows through the regenerative air dryer. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 43 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 27 A solenoid valve at the top of each spring regulates airflow into and out of the air spring. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 44 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 28 Schematic showing Computer Command Ride (CCR) system. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 45 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 29 Schematic showing the shock control used in the RSS system. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 46 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 30 Bi-state dampers (shocks) use a solenoid to control fluid flow in the unit to control compression and rebound actions. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 47 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

Check the RPO Code • Whenever working on the suspension system check the RPO (regular production option) code for the type of suspension used. For example, the F 55 RPO may be called by a different name depending on the make and model of vehicle. Also, service procedures will be different on the same vehicle depending on whether it is equipped with an F 45 or an F 55 system. The General Motors vehicle RPO codes are on a sticker on the spare tire cover in the trunk or in the glove compartment. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 48 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 31 Solenoid valve controlled shock absorber circuit showing the left front (LF) shock as an example. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 49 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 32 A typical CCR module schematic. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 50 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 33 The three dampening modes of a CCR shock absorber. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 51 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TYPES OF ELECTRONIC SUSPENSION FIGURE 9– 34 Integral shock solenoid. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 52 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

What Are Self-Leveling Shocks? • • A German company, ZF Sachs, supplies a selfleveling shock absorber to several vehicle manufacturers, such as Chrysler for use on the rear of minivans, plus BMW, Saab, and Volvo. The self-leveling shocks are entirely self-contained and do not require the use of height sensors or an external air pump. The shock looks like a conventional shock absorber but contains the following components: • • • Two reservoirs in the outer tube An oil reservoir (low-pressure reservoir) A high-pressure chamber Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 53 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

What Are Self-Leveling Shocks? • Inside the piston rod is the pump chamber containing an inlet and an outlet valve. When a load is placed in the rear of the vehicle, it compresses the suspension and the shock absorber. When the vehicle starts to move, the internal pump is activated by the movement of the body. Extension of the piston rod causes oil to be drawn through the inlet valve into the pump. When the shock compresses, the oil is forced through the outlet valve into the high-pressure chamber. The pressure in the oil reserve decreases as the pressure in the high-pressure chamber increases. The increasing pressure is applied to the piston rod, which raises the height of the vehicle. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 54 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

What Are Self-Leveling Shocks? • When the vehicle’s normal height is reached, no oil is drawn into the chamber. Because the shock is mechanical, the vehicle needs to be moving before the pump starts to work. It requires about 2 miles of driving for the shock to reach the normal ride height. The vehicle also needs to be driven about 2 miles after a load has been removed from the vehicle for it to return to normal ride height. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 55 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

What Are Self-Leveling Shocks? FIGURE 9– 35 A typical ZF Sachs self-leveling shock, as used on the rear of a Chrysler minivan. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 56 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

AUTOMATIC LEVEL CONTROL (ALC) • • • Vehicles that have an air inflator system as part of the ALC system also have an air inflator switch. The air inflator switch is an input to the ALC and AS system. The inflator switch is used to control the air inflator system operation and provides a signal to the ALC or AS module to initiate compressor activation. With the ignition on, the driver can turn the system to ON. The switch will command the compressor to run for up to 10 minutes, allowing time to inflate a tire or other items requiring air. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 57 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

AUTOMATIC LEVEL CONTROL (ALC) • • INFLATOR OR COMPRESSOR RELAY COMPRESSOR • • AIR DRYER EXHAUST SOLENOID Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 58 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

AUTOMATIC LEVEL CONTROL (ALC) FIGURE 9– 36 Schematic of the ALC system. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 59 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

AUTOMATIC LEVEL CONTROL (ALC) FIGURE 9– 37 Air compressor assembly can be located at various locations depending on the vehicle. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 60 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

AUTOMATIC LEVEL CONTROL (ALC) FIGURE 9– 38 The exhaust solenoid is controlled by the rear integration module (RIM). Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 61 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

AUTOMATIC LEVEL CONTROL (ALC) FIGURE 9– 39 Schematic showing the rear integration module (RIM) and how it controls the ALC compressor. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 62 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

MAGNETO-RHEOLOGICAL (MR) SUSPENSION • MR fluid shocks use a working fluid inside the shock that can change viscosity rapidly depending on electric current sent to an electromagnetic coil in each device. • • The fluid is called magneto-rheological (MR) and is used in monotube-type shock absorbers. This type of shock and suspension system is called the magneto-rheological real-time damping (MRRTD) or chassis continuously variable realtime dampening magneto-rheological suspension (CCVRTMR). Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 63 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

MAGNETO-RHEOLOGICAL (MR) SUSPENSION FIGURE 9– 40 Vehicles that use magneto-rheological shock absorbers have a sensor located near each wheel, as shown on this C 6 Corvette. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 64 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

MAGNETO-RHEOLOGICAL (MR) SUSPENSION FIGURE 9– 41 The controller for the magneto-rheological suspension system on a C 6 Corvette is located behind the right front wheel. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 65 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

MAGNETO-RHEOLOGICAL (MR) SUSPENSION FIGURE 9– 42 A cutaway of a magneto-rheological shock absorber as displayed at the Corvette Museum in Bowling Green, Kentucky. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 66 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

Can Computer-Controlled Shock Absorbers and Struts Be Replaced with Conventional Units? • Maybe. If the vehicle was manufactured with or without electronic or variable shock absorbers, it may be possible to replace the originals with the standard replacement units. The electrical connector must be disconnected, and this may cause the control system to store a diagnostic trouble code (DTC) and/or turn on a suspension fault warning light on the dash. Some service technicians have used a resistor equal in resistance value of the solenoid or motor across the terminals of the wiring connector to keep the controller from setting a DTC. All repairs to a suspension system should be done to restore the vehicle to likenew condition, so care should be exercised if replacing electronic shocks with nonelectronic versions. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 67 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TROUBLESHOOTING REAR ELECTRONIC LEVELING SYSTEMS • • The first step with any troubleshooting procedure is to check for normal operation. Some leveling systems require that the ignition key be on (run), while other systems operate all the time. Begin troubleshooting by placing approximately 300 lb (135 kg) on the rear of the vehicle. If the compressor does not operate, check to see if the sensor is connected to a rear suspension member and that the electrical connections are not corroded. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 68 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

TROUBLESHOOTING REAR ELECTRONIC LEVELING SYSTEMS FIGURE 9– 43 Most electronic level-control sensors can be adjusted, such as this General Motors unit. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 69 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

SUMMARY 1. 2. 3. 4. 5. 6. General Motors uses seven types of electronic suspension under many different names. Suspension height sensors and steering wheel (handwheel) position sensors are used in many systems. A vehicle speed sensor signal is used to control the suspension at various speeds. Many electronic suspension systems use a lateral accelerometer sensor, which signals the suspension computer when the vehicle is rapidly accelerating, braking, or cornering. Solenoids and motors are used to control the suspension movement by moving valves in the shock absorbers or air springs. An air pump and air shocks are used to raise the rear of the vehicle to compensate for a heavy load. Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 70 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

REVIEW QUESTIONS 1. 2. 3. 4. What type of sensor is usually used on electronically controlled suspensions to sense the height of the vehicle? Why is the vehicle speed sensor used as input for many electronic suspension systems? What is a lateral accelerometer sensor and why is it used? Why does the output side of the suspension air compressor contain a desiccant? Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 71 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

CHAPTER QUIZ 1. What type of sensor is used as a height sensor on vehicles equipped with an electronically controlled suspension? a. b. c. d. Hall-effect Photo cell Potentiometer All of the above Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 72 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

CHAPTER QUIZ 2. Which sensors do most vehicles use if equipped with electronic suspension? a. b. c. d. Height sensors Steering wheel position sensors Lateral accelerometer sensors All of the above Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 73 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

CHAPTER QUIZ 3. A lateral acceleration sensor is used to provide the suspension control module with feedback regarding ____ force. a. b. c. d. Cornering Acceleration Braking All of the above Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 74 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

CHAPTER QUIZ 4. A steering wheel position sensor is being discussed. Technician A says that the sensor is used to determine the direction the steering wheel is turned. Technician B says that the sensor detects how fast the steering wheel is turned. Which technician is correct? a. b. c. d. Technician A only Technician B only Both Technicians A and B Neither Technician A nor B Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 75 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

CHAPTER QUIZ 5. Technician A says that an electronic control module used in the suspension system is the same as that used for engine control. Technician B says that most electronically controlled suspension systems use a separate electronic control module. Which technician is correct? a. b. c. d. Technician A only Technician B only Both Technicians A and B Neither Technician A nor B Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 76 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

CHAPTER QUIZ 6. What type of actuator is used on electronically controlled suspensions? a. b. c. d. Solenoid Electric motor Either a or b Neither a nor b Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 77 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

CHAPTER QUIZ 7. Why is the typical rear load-leveling system connected to the ignition circuit? a. b. c. d. To keep the system active for a given time after the ignition is switched off To prevent the system from working unless the ignition key is on To keep the compressor from running for an extended period of time All of the above Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 78 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

CHAPTER QUIZ 8. Which sensor can be tested by unbolting the sensor and with the ignition on, engine off (KOEO), looking at the scan tool data? a. b. c. d. “G” sensor Wheel speed sensor Vehicle speed sensor Suspension sensor Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 79 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

CHAPTER QUIZ 9. The firm setting is usually selected by the electronic suspension control module whenever which of the following occurs? a. b. c. d. High speed Rapid braking Rapid acceleration All of the above Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 80 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.

CHAPTER QUIZ 10. Which of the following is the least likely sensor to cause an electronic suspension fault? a. b. c. d. Yaw sensor Throttle position (TP) sensor Steering wheel position sensor Vehicle speed sensor Automotive Steering, Suspension and Alignment, 5/e By James D. Halderman 81 Copyright © 2010, 2008, 2004, 2000, 1995 Pearson Education, Inc. , Upper Saddle River, NJ 07458 • All rights reserved.