Communication Fault
Communication fault
Checking the wiring
The diagnostic trouble code indicates that communication between the central electronic module (CEM) and the alternator control module (ACM) (not vehicles with a V8 engine), the left camera module (LCM) (optional extra) and the right camera module (RCM) (optional extra) is inoperative. This could be due to a fault in the signal lead between the control modules or a damaged communication unit in one or all of the control modules.
Note! All vehicles from and including model year 2005 are equipped with a signal cable to the Left Camera Module (LCM) / Right Camera Module (RCM) even if the vehicle is not equipped with BLIS system. This means that measurements must always be carried out up to the 12-pin connector in the external doors when the diagnostic trouble code (DTC) has been detected on LIN bus 2.
Check the signal lead between the central electronic module (CEM) and the alternator control module (ACM) for an open circuit or shorting to ground.
Take readings between:
- Central electronic module (CEM) #C16 (#16) and alternator control module (ACM) #B1.
For vehicles without the Blind Spot Indication System (BLIS)
Check the signal cable between the Central Electronic Module (CEM) and the 12-pin connector in the outer doors. Check for an open-circuit. Check for a short-circuit to ground.
Check the connector in both doors.
Take readings between:
- Central Electronic Module (CEM) D24 (#24) and the 12 pin connector in the external doors terminal #12.
For vehicles equipped with the Blind Spot Indication System (BLIS)
Check the signal lead between the central electronic module (CEM) and the left camera module (LCM) for an open circuit or shorting to ground.
Take readings between:
- Central electronic module (CEM) #D24 (#24) and left camera module (LCM) #5.
Check the signal lead between the central electronic module (CEM) and the right camera module (RCM) for an open circuit or shorting to ground.
Take readings between:
- Central electronic module (CEM) #D24 (#24) and right camera module (RCM) #5.
Also check intermediate connectors.
Remedy as necessary.
Other information
- Connecting the breakout box Connecting the Breakout Box, Central Electronic Module (CEM)
- Signal specification Pinout Values and Diagnostic Parameters
- Location of components Locations
- Replace the generator (GEN) for gasoline engines, see: Generator, replacement Service and Repair
- Replace the generator (GEN) for diesel engines, see: Generator (GEN), replacing Service and Repair
- Change the left camera module (LCM)/right camera module (RCM), see: Door mirror, replacing Service and Repair
- Checking wiring and terminals Checking Wiring And Terminals
Was a fault detected?
Yes - Fault Found
No - Checking the component
-------------------------------------------------
Checking the component
For vehicles equipped with the Blind Spot Indication System (BLIS)
The LEDs should flash three times whenever the Blind Spot Indication System (BLIS) is activated.
Switch on the ignition to check the right and left sides.
If any LED fails to flash three times on activation, try changing the control module on that side.
If both LEDs flash three times on activation, try changing the alternator control module (ACM)
For vehicles without the Blind Spot Indication System (BLIS)
Try changing the alternator control module (ACM).
Select the desired alternative:
1. Change the alternator control module (ACM).
2. Change the left camera module (LCM) / right camera module (RCM).
Select required alternative.
1 - Replacing the control module
2 - Replacing the control module
-------------------------------------------------
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
------------------------
FAULT-TRACING FAILED - FAULT-TRACING FAILED
Attempt New Test - Checking the wiring
-------------------------------------------------
Replacing the control module
Try a new alternator control module (ACM).
Remedy as necessary.
Other information
- Replace the generator (GEN) for gasoline engines, see: Generator, replacement Service and Repair
- Replace the generator (GEN) for diesel engines, see: Generator (GEN), replacing Service and Repair
Continue - Verification
-------------------------------------------------
Replacing the control module
Try changing the control module on the side where the LED failed to flash.
Remedy as necessary.
Other information
- Change the control module, see: Door mirror, replacing Service and Repair
Continue - Verification
-------------------------------------------------
Verification
Hint: After carrying out the repair, check that the fault has been remedied.
- Ignition off
- Reinstall the connectors, components etc.
- Ignition on
- Start the engine and run it to normal operating temperature.
Click on the VCT2000 symbol to read off the status of the generator (GEN).
Check that the read out shows OK.
Is the status given as OK?
Yes - VERIFIED
No - VERIFICATION FAILED
------------------------
VERIFIED - Fault Found
VERIFICATION FAILED - Fault-tracing information
-------------------------------------------------
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 that the light emitting diodes flash three times when the system is activated.
Did the light emitting diodes flash three times?
Yes - VERIFIED
No - VERIFICATION FAILED
------------------------
VERIFIED - Fault Found
VERIFICATION FAILED - Fault-tracing information
-------------------------------------------------