Speed Signal

Fault Symptom.
Somewhat poorer idle air control when driving in stop-and-go traffic.

Diagnostic Procedure.
1. Connect the ISAT and activate the command "WHEEL SPEED RF" in the "READ FUNCTIONS" menu. Drive the car and compare the speed shown on the ISAT's display with that of the car speedometer.

If the speeds coincide, continue at "Before Replacing Control Module" for further diagnostic instructions. Before Replacing A Control Module
If the speeds do not coincide, continue with step 2.

2. With the ignition switched OFF, connect a BOB to the MOTRONIC control module and cable.

Raise the car, turn the ignition switch to the DRIVE position and rotate the right-hand front wheel. The voltage measured across pins 9 and 14 should now change between 0 and 10 V.

If it does not, continue at step 3.

3. Check the lead between pin 9 of the MOTRONIC control module and pin 7 of the ABS control module for continuity/shorting.

If the lead is OK, check the output signal from pin 7 of the ABS control module. Check ABS fault diagnosis.