Contenu
The anti-lock braking system (ABS) and Traction Control systems in your Grand Prix both use the ABS wheel-speed sensors and modulator valve assembly to control wheel slip. The ABS system monitors the wheel-speed sensors and relieves brake pressure on a wheel that it senses is nearing lock-up. The Traction Control system monitors the same wheel-speed sensor and applies brake pressure to any wheel it senses over accelerating. Diagnosis of these systems is accomplished using a scan tool and the cars on-board computer diagnostics function.
Step 1
Check the tires for proper wheel size and check the fluid level in master cylinder. Improper tire size, such as two different sizes, will cause the wheels to turn at different speeds and may set a false code when the computer senses this as potential wheel lock-up. Low fluid level in the brake master cylinder will result in shutdown of the ABS and Traction Control system to prevent introduction of air into the brake system.
Step 2
Turn the ignition key off and insert the scan tools connector into the vehicles diagnostic connector. The diagnostic connector in OBD-II equipped Grand Prix is located under the drivers side of the dash near the steering column. Turn the ignition key on and retrieve trouble codes according to the instructions supplied with the scan tool. In most cases you will select "Read Codes" from the onscreen menu or push the "Read" button on the front of the scan tool to retrieve codes. Go to step two if the code indicates a wheel speed sensor fault or step five if the codes indicates a solenoid fault.
Step 3
Select "Data" from the onscreen menu and scroll through the list until wheel speed sensor data is displayed on the screen. Test drive the car while monitoring the wheel speed signals, indicated by the fault code, on the scan tool. If the wheel speed signal is different from the remaining wheel speed signals, test the resistance of the sensor.
Step 4
Unplug the faulty wheel speed sensor, located on the back of the wheel bearing and hub assembly at each wheel in the Grand Prix and test the resistance of the sensor using your digital volt/ohm meter set to read resistance. The resistance of a good wheel speed sensor will be1k ohms +/- 10 percent. Replace the sensor if the meter shows 0 ohms, infinite ohms, or the resistance is not 1k ohms +/- 10 percent.
Check fuses in the fuse block under the dash and under the hood. The fuses for the ABS and Traction Control systems are marked on the body of the fuse blocks. Replace any faulty fuses before continuing with the tests. Unplug the modulator valve assembly located on the drivers side of the passenger compartment near the master cylinder and test the resistance of solenoids using you digital volt/ohm meter. Replace the modulator valve assembly if 0 ohms or infinite resistance are measured at the assembly.
Items you will need
- Automotive scan tool
- Digital volt/ohm meter
