Component Tests

PROCEDURE BEFORE ECM REPLACEMENT

When all the checks have been carried out in accordance with the diagnostic procedures program under the diagnostic trouble code concerned or through manual fault diagnosis without any fault having been detected, it is natural to assume that the ECM is faulty.

Therefore, go through all the following points very carefully before definitely pinpointing the Motronic control module as the cause of the fault.

1. Check once more that all the items for checking in the fault diagnosis routine for the relevant diagnostic trouble code have been carried out.

2. Study the wiring diagram of the circuit in question and make sure you understand how it works. Relevant parts of the technical description and the electrical principles of operation described in Description and Operation and in wiring diagrams may be of assistance in this respect.

3. Check all grounding points. If you have already done so, do it once again. Check that power ground and sensors are physically and electrically separated from each other.

4. Check the voltage supply to the ECM.

5. Model year 1993 repair statistics show that the majority of all control modules returned in connection with warranty repairs were in perfect working order.

Unnecessary control module replacement represents a major cost for Saab Automobile and Saab dealers. Give careful thought to all possible causes of a fault before changing the control module.

When trying a different control module for testing purposes, always refit the original unit.

6. If the fault persists in spite of this, the Motronic control module will have to be changed.