+15 power supply
Symptom: The alarm is not set off when the ignition is switched on and the alarm is armed.
Fault symptom
The alarm is not set off when the ignition is switched on and the alarm is armed.
Diagnostic procedure
1 Check fuse 17.
|
-
|
Check that fuse 17 is intact and live.
|
|
-
|
Connect the test lamp to the fuse and a good grounding point.
|
With the ignition switch in the "ON" (+15) position, the test lamp should light up.
Is the test lamp on?
Continue with point 2.
Continue fault diagnosis as described in Service Manual 3:2 Electrical system, "+15 power supply".
2 Check the electronic control module's +15 power supply
|
-
|
Unplug connector H33-3.
|
|
-
|
Connect the test lamp to pin 25 of connector H33-3 and a good grounding point.
|
|
-
|
Turn the ignition switch to the "ON" (+15) position.
|
The test lamp should light.
Is the test lamp on?
Continue with point 3.
Continue with point 6.
3 Check the engine management system's +15 power supply
|
-
|
Connect a jumper lead between pins 25 and 18 of connector H33-3.
|
|
-
|
Turn the ignition switch to the "ON" (+15) position.
|
The "CHECK ENGINE" lamp (MIL) in the main instrument display panel should light up.
Is the "CHECK ENGINE" lamp on?
Continue with point 7.
Continue with point 4.
4 Check the wiring between connectors H33-3 and H33-4.
Check the wiring harness for continuity between pin 18 of connector H33-3 and pin 21 of connector H33-4.
The resistance should be < 1 ohm.
Is the resistance correct?
Continue with point 5.
Repair or replace the wiring harness.
5 Check the wiring connected to the engine management system
Conduct a continuity test on the cable assembly between connector H33-4, pin 21 and
|
-
|
Trionic control module, pin 60
|
|
-
|
Motronic 2.10.3 control module, pin 27
|
|
-
|
Motronic 2.8.1 control module, pin 27
|
depending on the engine version.
The resistance should be < 1 ohm.
Is the resistance correct?
Continue fault diagnosis as described in Service Manual 2:7 "Engine management system TRIONIC", "MOTRONIC 2.10.3" or "MOTRONIC 2.8.1".
Repair or replace the wiring harness.
6 Check the wiring connected to fuse 17
|
-
|
Connect the test lamp to fuse 17 and a good grounding point.
|
|
-
|
Turn the ignition switch to the "ON" (+15) position.
|
The test lamp should light.
Is the test lamp on?
Check and repair or replace the wiring.
Continue fault diagnosis as described in Service Manual 3:2 Electrical system, "+15 power supply".
7 Check the wiring connected to the electronic control module
|
-
|
Unplug the control module.
|
|
-
|
Check the wiring harness for continuity between: - connector H33-3 (pin 25) and the electronic control module (pin 10). - connector H33-3 (pin 18) and the electronic control module (pin 22).
|
The resistance should be < 1 ohm.
Is the resistance correct?
Continue with point 8.
Repair or replace the wiring harness.
8 Final check
Start the car and check to see if the fault symptom remains.
Is the problem still present?
See "Before replacing a control module".
The remedial measures taken were correct or the fault is of intermittent nature.
