Automatic Lighting Control Unit

DTC Troubleshooting: U128D

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 Troubleshooting - B-CAN System Diagnosis Test Mode A.

1. Clear the DTCs with the HDS.

2. Turn the ignition switch to LOCK (0) and then back to ON (II).

3. Wait for at least 6 seconds.

4. Check for DTCs with the HDS.

Is DTC U128D indicated?

YES -

Go to step 5.

NO -

Intermittent failure, the system is OK at this time. Check for loose or poor connections between the automatic lighting control unit and the gauge control module.

5. From the BODY ELECTRICAL SYSTEM SELECT menu, select B-CAN CONTROL UNITS INFORMATION, and then select CHECK CONNECTED CONTROL UNITS.

Is the gauge control module detected?

YES -

Go to step 9.

NO -

Go to step 6.

6. Measure the voltage between body ground and gauge control module 32P connector terminals No. 16 and No. 32 individually.





Is there battery voltage?

YES -

Go to step 8.

NO -

Go to step 7.

7. Check the No. 23(10 A) fuse in the under-hood fuse/relay box and the No. 10(7.5 A) fuse in the under-dash fuse/relay box.

Are the fuses OK?

YES -

Repair an open or high resistance in the No. 23(10 A) and/or No. 10(7.5 A) fuse circuit.

NO -

Replace the fuse(s). If the fuse blows again, repair a short to ground in the No. 23(10 A) and/or No. 10 (7.5 A) fuse circuit.

8. Measure the voltage between body ground and gauge control module 32P connector terminals No. 13, No. 17, and No. 18 individually.





Is there less than 0.2 V?

YES -

Go to step 9.

NO -

Repair an open or high resistance in the ground wire or poor ground (G401).

9. Turn the ignition switch to LOCK (0).

10. Disconnect the gauge control module 32P connector.

11. Disconnect the automatic lighting control unit connector 14P.

12. Check for continuity between automatic lighting control unit 14P connector terminals No. 3 and No. 4 and the gauge control module 32P connector terminals No. 19 and No. 20 respectively.





Is there continuity?

YES -

Replace the gauge control module Service and Repair.

NO -

Repair an open or poor connection in the B-CAN wire between the gauge control module and the automatic lighting control unit.