DTC Troubleshooting: U128D
DTC U128D: Auto Light Control Unit Lost Communication with Gauge Control Module
DTC Description
DTC
U128D Auto Light Control Unit Lost Communication with Gauge Control Module
  

NOTE: If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A.

1.
Problem verification:

Problem verification
?1.
Clear the DTCs with the HDS.


?2.
Turn the vehicle to the OFF (LOCK) mode and then the ON mode.

?3.
Wait for at least 6 seconds.

?4.
Check for DTCs with the HDS.
DTC Description
DTC
U128D Auto Light Control Unit Lost Communication with Gauge Control Module
  

Is DTC U128D indicated?

     
YES
     
     
     
Go to step 2.
     
NO
     
     
     
Intermittent failure, the system is OK at this time. Check for loose or poor connections.?
2.
Determine possible failure area (gauge control module power and ground, B-CAN line):

Determine possible failure area (gauge control module power and ground, B-CAN line)
?1.
Select GAUGES from the BODY ELECTRICAL SYSTEM SELECT menu, and then select DATA LIST.

Does the DATA LIST appear?

     
YES
     
     
     
Go to step 5.
     
NO
     
     
     
Go to step 3.
3.
Fuse check:

Fuse check
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Check the following fuse.
Fuse
No. B29

Is the fuse OK?

     
YES
     
     
     
Go to step 4.
     
NO
     
     
     
Replace the fuse. If the fuse blows again, repair a short to ground in the No. B29 fuse circuit.?
4.
Open wire check (+B BACK UP line):

Open wire check (+B BACK UP line)
?1.
Disconnect the following connector.
Gauge control module 32P connector

?2.
Measure the voltage between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Gauge control module 32P connector: disconnected
Test point 1
Gauge control module 32P connector No. 16
Test point 2
Body ground

Is there battery voltage?

     
YES
     
     
     
Repair an open or high resistance in the ground wire or poor ground (G401).?
     
NO
     
     
     
Repair an open or high resistance in the wire.?
5.
Open wire check (B-CAN_H wire):

Open wire check (B-CAN_H wire)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connectors.
Gauge control module 32Pconnector
Automatic lighting control unit-sensor 5P connector (USA and Canada models)
Automatic lighting control unit-sensor 7P connector (Mexico models)

?3.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Gauge control module 32P connector: disconnected
Automatic lighting control unit-sensor 5P connector (USA and Canada models): disconnected
Automatic lighting control unit-sensor 7P connector (Mexico models): disconnected
Test point 1
Automatic lighting control unit-sensor 5P connector No. 1 (USA and Canada models)
Automatic lighting control unit-sensor 7P connector No. 6 (Mexico models)
Test point 2
Gauge control module 32P connector No. 23

Is there continuity?

     
YES
     
     
     
The B-CAN_H wire is OK. Go to step 6.
     
NO
     
     
     
An open or poor connection in the B-CAN_H wire.?
6.
Open wire check (B-CAN_L wire):

Open wire check (B-CAN_L wire)
?1.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Gauge control module 32P connector: disconnected
Automatic lighting control unit-sensor 5P connector (USA and Canada models): disconnected
Automatic lighting control unit-sensor 7P connector (Mexico models): disconnected
Test point 1
Automatic lighting control unit-sensor 5P connector No. 2 (USA and Canada models)
Automatic lighting control unit-sensor 7P connector No. 7 (Mexico models)
Test point 2
Gauge control module 32P connector No. 24

Is there continuity?

     
YES
     
     
     
     
NO
     
     
     
An open or poor connection in the B-CAN_L wire.?