+ 15 Supply

Fault symptom
The alarm is not set off when the ignition is switched on and the alarm is armed.

Action
1 Check fuse 17
Check fuse 17 and check that there is voltage to the fuse.
Connect the test lamp between the fuse and a safe grounding point.
With the ignition in the "ON" (+ 15) position, the test lamp should light.
If the test lamp lights, proceed to point 2.
If the test lamp does not light, continue fault diagnosis in Service Manual 3:2 Electrical system, "+ 15 Power Supply".

2 Check + 15 supply to the control module
Unplug connector H33-3.
Connect the test lamp between H33-3, pin 25 and a safe grounding point.
Turn the ignition key to the "ON" (+ 15) position.
The test lamp should light.
If the test lamp lights, proceed to point 3.
If the test lamp does not light, proceed to point 6.

3 Check + 15 supply to the engine control system
Loop in connector H33-3 between pin 25 and pin 18.
Turn the ignition key to the "ON" (+ 15) position.
The "CHECK ENGINE" (MIL) lamp in the main instrument should light.
If the "CHECK ENGINE" (MIL) lamp lights, proceed to point 7.
If the "CHECK ENGINE" (MIL) lamp does not light, proceed to point 4.






4 Check the cable between connectors H33-3 and H33-4.
Conduct a continuity test on the cable assembly between connector H33-3, pin 18 and connector H33-4, pin 21.
The resistance should be < 1 Ohm.
If the resistance is incorrect, take action on the cable assembly.
If the resistance is correct, proceed to point 5.

5 Check the cable assembly to the engine control system
Conduct a continuity test on the cable assembly between connector H33-4, pin 21 and
- Trionic control module, pin 60
- Motronic 2.10.2 control module, pin 27
- Motronic 2.8.1 control module, pin 27
depending on the engine alternative.
The resistance should be < 1 Ohm.
If the resistance is incorrect, take action on the cable assembly.
If the resistance is correct, continue fault diagnosis in Engine Management System,
"Trionic" or "Motronic".






6 Check the cable assembly to fuse 17
Connect the test lamp between fuse 17 and a safe grounding point.
Turn the ignition key to the "ON" (+ 15) position. The test lamp should light.
If the test lamp lights, check and take action on the cable assembly.
If the test lamp does not light, continue fault diagnosis in Service Manual 3:2 Electrical system, "+ 15 Power Supply".

7 Check the cable assembly to the control module
Unplug the control module.
Conduct a continuity test on the cable assembly between:
- Connector H33-3, pin 25 and the control module, pin 10
- Connector H33-3, pin 18 and the control module, pin 22. The resistance should be < 1 Ohm.
If the resistance is incorrect, take action on the cable assembly.
If the resistance is correct, proceed to point 8.

8 Final test
Start the car and check to see if the fault symptom remains.
If the problem remains, proceed to Before Control Module Replacement.