Signal Too Low

Signal too low

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 ohms 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 Connecting the Breakout Box
- For information about signals, see Signal specification Signal Specification, Upper Electronic Module (UEM)
- To access or replace the interior lighting, see Replacing interior lighting Service and Repair
- To fault-trace wiring and terminals, see Checking wiring and terminals Checking Wiring And Terminals.





Was a fault detected?

Yes - Verification

No - No Fault Found

-------------------------------------------------

Verification




Verification

Verification

Hint: After carrying out the repair, check that the fault has been remedied.








- Ignition off
- Reinstall the connectors, components etc.
- Ignition on.
Check whether Extended X supply (EXT_X) is working.





Is each component working (sun roof, mirror lamps in sun visor, rain sensor and interior lighting)?

Yes - VERIFIED

No - VERIFICATION FAILED

------------------------

VERIFIED - Fault Found

VERIFICATION FAILED - Fault-tracing information

-------------------------------------------------

Fault-tracing information




Information

Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.

Do you want to exit fault-tracing?

Yes - FAULT-TRACING FAILED

No - Attempt New Test

------------------------

Attempt New Test - Checking for a short-circuit

FAULT-TRACING FAILED - No Fault Found

-------------------------------------------------