P0501

VEHICLE SPEED SIGNAL





Fault Symptoms.
CHECK ENGINE lamp (MIL) on.
SHIFT UP lamp not working
ABS warning lamp may be on.

Conditions.
P0501
^ Engine speed above 2000 rpm.
^ Engine load greater than 3.0 ms.
^ Vehicle speed slower than 10 km/h for more than 7 seconds.

Diagnostic Help.
A vehicle speed signal can be obtained with the ISAT scan tool.
- Select "READ FUNCTIONS".
- Select "CAR SPEED".

The ISAT scan tool should show the current wheel speed.

Drive the car and compare the ISAT scan tool reading with the car's speedometer.

Check The Wiring.
Intermittent faults may occur as a result of temporary short circuits and breaks in the wiring. Jiggle the wiring at several points and in different directions to ascertain whether the wiring harness, including any connectors, is causing the trouble. Observe the multimeter, ISAT scan tool or test lamp while doing this.





Diagnostic Procedure.
1. Check the ABS diagnostic trouble codes

- Connect the ISAT Scan Tool.
- Ignition switch in the ON position.
- Select "ABS M96".
- Obtain readings of the diagnostic trouble codes, if any.

Diagnostic trouble codes for the right-hand front wheel sensor are B1376 and B1377.

Does the ISAT scan tool show diagnostic trouble code B1376 or B1377

YES: Continue fault diagnosis in the Brakes. Then carry out a final check according to point 3.
NO: Continue with point 2.





2. Check the wheel speed signal

- Jack up the front end of the car.
- Unplug the control module's 88-pin connector.
- Turn the ignition switch. to the ON position.
- Connect the test lamp to pins 26 and 79 of the female connector.
- Spin the right-hand front wheel.

The test lamp should flash.

Test lamp flashing?
YES: Continue with point 3.
NO: Check the lead between pin 26 of the ABS control module and pin 79 of the Motronic control module for continuity and shorting. Repair or replace the lead if necessary. If the lead is OK, continue fault diagnosis in the Brakes.





3. Final check

- Clear the diagnostic trouble code.
- Implementation of driving cycle:
^ Drive the car at varying engine loads and rpm for 5 minutes.
- Evaluation of driving cycle:
^ Connect the ISAT Scan Tool.
^ Select "READ FUNCTIONS".
^ Select "CAR SPEED".
^ Check whether the ISAT scan tool shows the same speed as the speedometer.

Does the ISAT scan tool show a different speed?
YES: Continue at "Before Replacing a Control Module". Component Tests and General Diagnostics
NO: The steps taken to rectify the fault were correct.