Left Rear Wheel Acceleration
The rear wheel speed sensors monitor the speed of each wheel by placing a magnetic coupling next to a toothed ring mounted in the hub and bearing assembly. The signal changes with the wheel speed signal change over 16 km/h (10 mph) in 8 milliseconds while the car is moving, the control module will disable ABS and turn On the antilock telltale lamp.
Code Parameters
Code 27 sets if:
This code can set anytime the vehicle is moving and not in ABS braking.
This code can set in conjunction with code 23.
The vehicle should be driven at speeds above 64 km/h (40 mph) to check for reoccurrence of this failure.
Diagnostic Aids
Before proceeding with the trouble tree, make a thorough visual inspection of the wheel speed sensor circuitry. Closely inspect the inline connector(s) since this is the most likely area for opens or shorts.
Connect the Scan tool, spin the wheel by hand, and monitor the wheel speed. Make a comparison with other wheels.
| • | Visually inspect sensors and connectors. Check the wheel speed sensor ring for tooth damage or out-of-round condition. |
| • | ABS system is very sensitive to ring damage. Inserting screwdrivers, crowbars, etc. into the ring area and prying against the ring will cause damage. |
| • | The distance between the wheel speed sensor and wheel speed sensor ring should be between 0.60-1.78 mm (0.025 and 0.070 in.). |
| • | Using an ohmmeter to check resistance, shake wires to locate intermittents. For sensor resistance, refer to the following chart: |
Temp (°C) | Temp (°F) | Minimum Range | Maximum Range |
|---|---|---|---|
--34 to 4 | -30 to 40 | 1250 ohms | 1800 ohms |
5 to 43 | 41 to 110 | 1500 ohms | 2100 ohms |
44 to 93 | 111 to 200 | 1750 ohms | 2500 ohms |
Check the tightness of the female terminal grip with a spare male terminal
When attempting to diagnose an intermittent problem, use the Scan tool to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem.
Select Malf History from Scan tool ABS menu.
Intermittents or opens suspected to be at the connectors can be detected by using a diagnostic service probe.
