DTC 25: Left Front Excessive Wheel Speed Variation: Description

Test detects condition when left front wheel acceleration or deceleration is beyond specified limits.

1. Test drive vehicle. Using scan tool, select DATA LIST. Monitor left front wheel speed while decelerating from 35 MPH to zero. If wheel speed input matches vehicle speed, left front wheel speed sensor is currently functioning correctly. See DIAGNOSTIC AIDS . If wheel speed input does not match vehicle speed, go to next step.
2. Turn ignition switch to LOCK position. Raise and support left front wheel. Inspect hub and bearing assembly for perceptible movement. Ensure all components are in acceptable condition. Repair as needed. If all components are okay, go to next step.
3. Inspect speed sensor, wiring harness and applicable connections. Ensure all components are in acceptable condition. Repair as needed. If all components are okay, go to next step.
4. Disconnect harness connector from left front wheel speed sensor. Measure resistance between component terminals. If resistance is 920-1220 ohms at 68°F (20°C), go to next step. If resistance is not as specified, replace wheel speed sensor.
5. Measure AC voltage between component terminals while spinning wheel. Voltage should be at least 100 mV. Voltage will increase with wheel speed. If voltage is as specified, go to next step. If voltage is not as specified, remove wheel speed sensor and inspect sensor ring for damage. Replace as needed. If sensor ring is okay, replace wheel speed sensor.
6. Measure resistance between ground and terminal No. 2 (Blue/Black wire) on left front wheel speed sensor connector. If resistance measured is infinite, go to next step. If resistance measured is not infinite, replace wheel speed sensor.
7. Turn ignition switch to LOCK position. Disconnect EBCM harness connectors. Turn ignition switch on. Measure voltage between ground, and terminals No. 5 (Blue wire) and No. 16 (Blue/Black wire) on EBCM 24-pin harness connector. If voltage is 1 volt or less for both circuits, go to next step. If voltage is greater than 1 volt for either circuit, repair suspect circuit for short to voltage.
8. Turn ignition to LOCK position. Measure resistance between ground, and terminals No. 5 (Blue wire) and No. 16 (Blue/Black wire) on EBCM 24-pin harness connector. If resistance measured for both circuits is infinite, go to next step. If resistance measured on either circuit is not infinite, repair suspect circuit for short to ground.
9. Check continuity of circuits between left front wheel speed sensor harness connector and terminals No. 5 (Blue wire) and No. 16 (Blue/Black wire) on EBCM 24-pin harness connector. If continuity exists in both circuits, go to next step. If continuity does not exist in either circuit, repair suspect circuit for open.
10. Check continuity between terminals No. 5 (Blue wire) and No. 16 (Blue/Black wire) on EBCM 24-pin harness connector. If continuity exists, repair short between Blue wire and Blue/Black wire. If continuity does not exist, reconnect all components. Repeat step 1). If wheel speed input does not match vehicle speed or DTC is reset, replace EBCM.