DTC U128D: MICU Lost Communication With Gauge Control Module

DTC Description	DTC
U128D MICU 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 - Refer to: Body Electrical Troubleshooting - B-CAN System Diagnosis Test Mode A - Initial Communication and DTC Checks Body Electrical Troubleshooting - B-CAN System Diagnosis Test Mode 1 and Test Mode 2 (without the HDS)Body Electrical Troubleshooting - B-CAN System Diagnosis Test Mode B - Control Unit Not Communicating Body Electrical Troubleshooting - B-CAN System Diagnosis Test Mode C - No DTCs and Output Won't Shut OFF Body Electrical Troubleshooting - B-CAN System Diagnosis Test Mode D - No DTCs and Output Won't Turn ON .

NOTE: Refer to the Electrical Wiring Diagrams for the location of the under-dash fuse/relay box connectors.

1. 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 MICU Lost Communication With Gauge Control Module

Is DTC U128D indicated?

YES

Go to step 2.

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):
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:

1. Check the following fuses.

Fuse	No. A29 (10 A)
Location	Under-hood fuse/relay box

Is each fuse OK?

YES

Go to step 4.

Replace the fuse. If the fuse blows again, repair a short to ground in the No. A29 (10 A) fuse circuit.

4. Open wire check (+B BACK UP line):

1. Turn the vehicle to the OFF (LOCK) mode.

2. Disconnect the following connector.

Gauge control module connector A (32P)

3. Measure the voltage between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode Gauge control module connector A (32P): disconnected
Test point 1	Gauge control module connector A (32P) No. 1
Test point 2	Body ground

Is there battery voltage?

YES

Repair an open or high resistance in the ground wire or poor ground (G502).

Repair an open or high resistance in the wire.

5. Open wire check (B-CAN_H lines):

1. Turn the vehicle to the OFF (LOCK) mode.

2. Disconnect the following connector.

Under-dash fuse/relay box connector K (12P)

3. Check for continuity between test points 1 and 2.

Test condition

Vehicle OFF (LOCK) mode

Gauge control module connector A (32P): disconnected

Under-dash fuse/relay box connector K (12P): disconnected

Test point 1

Under-dash fuse/relay box connector K (12P) No. 2

Test point 2

Gauge control module connector A (32P) No. 30

Is there continuity?

YES

The B-CAN_H wire is OK. Go to step 6.

An open or poor connection in the B-CAN_H wire between the MICU and the gauge control module.

6. Open wire check (B-CAN_L lines):

1. Check for continuity between test points 1 and 2.