P1252

DIAGNOSTIC TROUBLE CODES P1251, P1252
CHECK ENGINE lamp (MIL), output from control module low/high or shorting to ground/batt+

Fault Symptom.
The CHECK ENGINE lamp does not light up when the ignition switch is turned to the DRIVE position

Condition
Shorting to ground/batt+ in the circuit to pin 22

Diagnostic Procedure.
1. Activate the ISAT command "CHECK ENGINE" in the "ACTIVATE" menu.

If the lamp cannot be activated or does not light up when the ignition switch is in the drive position, continue with step 2.

2. With the ignition switched OFF, connect a BOB to the MOTRONIC control module.
With the ignition switch in the DRIVE position, check whether the CHECK ENGINE lamp lights up when a jumper lead is connected across pins 14 and 22.

If it does not, check whether the lamp receives any current. Also check the lead and connector for continuity between pin 22 of the control module and the lamp.

3. The CHECK ENGINE lamp should light up when the control module grounds pin 22 if a diagnostic trouble code is generated or always when the ignition is switched ON.
Take a voltage reading across pins 37 and 22 on the BOB. Battery voltage should be present when the ignition is switched on.

4. If no faults can be detected after carrying out the above diagnostic procedure, clear all trouble codes and drive the car on the road to check whether any trouble codes are generated afresh.

If they are, continue at "Before Replacing Control Module" for further diagnostic instructions. Before Replacing A Control Module