Multiplex Integrated Control Unit

Control System DTCs

DTC Troubleshooting: U128D

DTC U128D : MICU Lost Communication With Gauge Control Module

NOTE:
* Refer to the Electrical Wiring Diagrams for the location of the under-dash fuse/relay box connectors.
* If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A.

1. Problem verification:

-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 2.
-NO- Intermittent failure, the system is OK at this time. Check for loose or poor connections.

2. Fuse check:

-1. Check the following fuses.










Is each fuse OK?
-YES- Go to step 3.
-NO- Replace the fuse. If the fuse blows again, repair a short to ground in the No. A29 (10 A) and/or No. B5 (10 A) fuse circuit(s).

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

-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.






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










Is there battery voltage?
-YES- The +B BACK UP wire is OK. Go to step 4.
-NO- Repair an open or high resistance in the wire.

4. Open wire check (IG1 METER line):

-1. Turn the ignition switch to ON (II).

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










Is there battery voltage?
-YES- The IG1 METER wire is OK. Go to step 5.
-NO- Repair an open or high resistance in the wire.

5. Open wire check (GND lines):

-1. Turn the ignition switch to LOCK (0).

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














Is there continuity?
-YES- The GND wires are OK. Go to step 6.
-NO- Repair an open or high resistance in the ground wire or poor ground (G502).

6. Open wire check (B CAN lines):

-1. Disconnect the following connector.






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










Is there continuity?
-YES- An open or poor connection in the B CAN-L wire between the MICU and the gauge control module.
-NO- An open or poor connection in the B CAN-H wire between the MICU and the gauge control module.