DTC U128D: Backup Control Unit Lost Communication With Gauge Control Module (Keyless Access Backup Control Unit)

DTC (Backup Control Unit)

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 .

1. Problem verification:

   - 1. Turn the vehicle to the ON mode.

   - 2. Clear the DTCs with the HDS.

   - 3. Turn the vehicle to the OFF (LOCK) mode and then the ON mode.

   - 4. Wait for at least 6 seconds.

   - 5. Check for DTCs with the HDS.

   DTC Description	DTC
   U128D Backup control unit lost communication with gauge control module

   Is DTC U128D indicated?

   YES 

   Go to step 2 below.

   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):

   - 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 below.

3. Fuse check:

   - 1. Check the following fuse.

   Fuse	No. B29 (10 A)
   Location	Under-hood fuse/relay box

   Is the fuse OK?

   YES 

   Go to step 4 below.

   NO 

   Replace the fuse. If the fuse blows again, repair a short to ground in the No. B29 (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 32P connector

   - 3. 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 line):

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

   - 2. Disconnect the following connectors.

   Keyless access control unit connector C (20P)

   Gauge control module 32P connector

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

   Test condition	Vehicle OFF (LOCK) mode
   	Gauge control module 32P connector: disconnected
   	Keyless access control unit connector C (20P): disconnected
   Test point 1	Keyless access control unit connector C (20P) No. 1
   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 below.

   NO 

   An open or poor connection in the B-CAN_H wire.

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

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

   Test condition	Vehicle OFF (LOCK) mode
   	Gauge control module 32P connector: disconnected
   	Keyless access control unit connector C (20P): disconnected
   Test point 1	Keyless access control unit connector C (20P) No. 11
   Test point 2	Gauge control module 32P connector No. 24

   Is there continuity?

   YES 

   The B-CAN_L wire is OK. Replace the keyless access control unit .

   NO 

   An open or poor connection in the B-CAN_L wire.