Operation CHARM: Car repair manuals for everyone.

P0501

VEHICLE SPEED SIGNAL





Fault Symptoms
CHECK ENGINE lamp (MIL) on.
SHIFT UP lamp not working.
Fuel shut-of in all gears.
ABS warning lamp may be on.

Conditions.
P0501
^ Engine speed > 2600 rpm.
^ No speed signal for 5 seconds.
^ High engine load.

Diagnostic
A vehicle speed signal reading 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 speed indicated on the 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 an ISAT scan tool.
- Turn the ignition switch to the ON position.
- Select "ABS M96".
- Obtain readouts of any diagnostic trouble codes.

Diagnostic trouble codes for the RH front wheel sensor are B1376 and B1377.

Does the ISAT scan tool show B1376 or B1377?

YES:
^ Continue fault diagnosis as described in the brake system. Then carry out a final check according to point 3.
NO:
^ Continue with point 2.





2 Check the wheel speed signal

- Raise the car at the front.
- Unplug the Motronic control module connector.
- Turn the ignition switch to the ON position.
- Connect the test lamp to the female connector, between:
^ pins 42 and 1.
- Spin the RH 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 42 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 brake system.





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 an ISAT scan tool.
^ Select "READ FUNCTIONS".
^ Select "CAR SPEED".

The ISAT scan tool should show the same speed as that indicated by the speedometer.

Is the ISAT scan tool reading incorrect?

YES:
^ Continue at "Before Replacing a Control Module". Component Tests and General Diagnostics
NO:
^ The steps taken to rectify the fault were correct.