Checking For A Short-Circuit
- Ignition off.
If all the functions that are supplied with power from the upper electronic module (UEM) via Extended X-supply (EXT_X) are not working (i. e. sun roof logic, mirror lamps in the sun visor, rain sensor or interior lighting), it can be assumed that either the cable between the upper electronic module (UEM) and the junction point 53/505 is short-circuited to ground or the wiring from the junction point to each component is short-circuited to ground.
First check the power supply cable between the upper electronic module (UEM) and each component. If the cable is short-circuited to ground, 0 Ω will be measured.
For mirror lamps in the sun visor, check the cable between the mirror lamp connector terminal #1 and the connector for the upper electronic module (UEM) terminal #A8. Check for a short-circuit to ground.
For sun roof and interior lighting, take readings on the cable between the connector for roof lamps terminal #A2 (and the sun roof module) and the connector for the upper electronic module (UEM) #A8. Check for a short-circuit to ground.
For rain sensor, take readings on the cable between the rain sensor connector terminal #A3 and the connector for the upper electronic module (UEM) terminal #A8. Check for a short-circuit to ground.
If all the readings result in a short-circuit to ground, it can be assumed that the fault is between the upper electronic module (UEM) #A8 and junction point 53/505.
Remedy as necessary.
Other information:
- To connect the breakout box, see CONNECTING THE BREAKOUT BOX
- For information about signals, see SIGNAL DESCRIPTION, UPPER ELECTRONIC MODULE (UEM)
- To access or replace the interior lighting, see INTERIOR LIGHTING, REPLACING
- To fault-trace wiring and terminals, see CHECKING WIRING AND TERMINALS .
Was a fault detected?
- YES
Refer to VERIFICATION
- NO
FAULT NOT FOUND: Troubleshooting has been completed.