DTC : U128D (Keyless Access Backup Control Unit: 9-Speed A/T) (2016 2017 2018)

DTC U128D  : Backup Control Unit Lost Communication with Gauge Control Module

DTC (Backup Control Unit)

NOTE: 

• If you have any loss of communication DTCs for the PCM, troubleshoot those DTCs first.
• 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. Clear the DTCs with the HDS.

   Clear DTCs

   - 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 Backup 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)

   -1. Select B-CAN CONTROL UNITS INFORMATION from the BODY ELECTRICAL SYSTEM SELECT menu, and then select CHECK CONNECTED CONTROL UNITS.

   - 2. Check the DETECT/NOT AVAILABLE information of the GAUGE CONTROL MODULE.

   Is DETECT indicated?

   YES 

   Go to step 9.

   NO 

   Go to step 3.

3. Fuse check

   -1. Check the following fuses.

   Fuse	No. A26 (10 A)
   Location	Under-hood fuse/relay box

   Fuse	No. C7 (15 A)
   Location	Under-dash fuse/relay box

   Fuse	No. D1 (7.5 A)
   Location	Auxiliary under-dash fuse/relay box

   Is each fuse OK?

   YES 

   Go to step 4.

   NO 

   Replace the fuse. If the fuse blows again, repair a short to ground in the No. A26 (10 A), No. C7 (15 A), and/or the No. D1 (7.5 A) fuse circuit(s).

4. Relay check

   -1. Check the following relay.

   Relay	DC-DC converter IG1 relay 1
   Location	Auxiliary under-dash fuse/relay box

   Is relay OK?

   YES 

   Go to step 5.

   NO 

   Replace the DC-DC converter IG1 relay 1.

5. Open wire check (+B BACKUP 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. 1 - Refer to: Gauge Control Module Connector for Inputs and Outputs (2016 2017 2018) .
   Test point 2	Body ground

   Is there battery voltage?

   YES 

   The +B BACKUP wire is OK. Go to step 6.

   NO 

   Repair an open or high resistance in the wire.

6. Open wire check (IG1 METER (DC/DC) line)

   -1. Turn the vehicle to the ON mode.

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

   Test condition	Vehicle ON mode Gauge control module 32P connector: disconnected
   Test point 1	Gauge control module 32P connector No. 17 - Refer to: Gauge Control Module Connector for Inputs and Outputs (2016 2017 2018) .
   Test point 2	Body ground

   Is there battery voltage?

   YES 

   The IG1 METER (DC/DC) wire is OK. Go to step 7.

   NO 

   Repair an open or high resistance in the wire.

7. Open wire check (GND, PGND lines)

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

   - 2. Check for continuity 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. 4 - Refer to: Gauge Control Module Connector for Inputs and Outputs (2016 2017 2018) .
   Test point 2	Body ground

   Test point 1	Gauge control module 32P connector No. 32 - Refer to: Gauge Control Module Connector for Inputs and Outputs (2016 2017 2018) .
   Test point 2	Body ground

   Is there continuity?

   YES 

   The GND and PGND wires are OK. Go to step 8.

   NO 

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

8. Open wire check (B-CAN lines)

   -1. Disconnect the following connector.

   Keyless access/TPMS control unit connector C (20P)

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

   Test condition	Vehicle OFF (LOCK) mode Gauge control module 32P connector: disconnected Keyless access/TPMS control unit connector C (20P): disconnected
   Test point 1	Gauge control module 32P connector No. 26 - Refer to: Gauge Control Module Connector for Inputs and Outputs (2016 2017 2018) .
   Test point 2	Keyless access/TPMS control unit connector C (20P) No. 1 - Refer to: Keyless Access/TPMS Control Unit Connector for Inputs and Outputs (2016 2017 2018) .

   Is there continuity?

   YES 

   An open or poor connection in the B-CAN_L wire between the keyless access/TPMS control unit and the gauge control module.

   NO 

   An open or poor connection in the B-CAN_H wire between the keyless access/TPMS control unit and the gauge control module.

9. Open wire check (B-CAN lines)

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

   - 2. Disconnect the following connectors.

   Gauge control module 32P connector

   Keyless access/TPMS control unit connector C (20P)

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

   Test condition	Vehicle OFF (LOCK) mode Gauge control module 32P connector: disconnected Keyless access/TPMS control unit connector C (20P): disconnected
   Test point 1	Gauge control module 32P connector No. 26 - Refer to: Gauge Control Module Connector for Inputs and Outputs (2016 2017 2018) .
   Test point 2	Keyless access/TPMS control unit connector C (20P) No. 1 - Refer to: Keyless Access/TPMS Control Unit Connector for Inputs and Outputs (2016 2017 2018) .

   Is there continuity?

   YES 

   An open or poor connection in the B-CAN_L wire between the keyless access/TPMS control unit and the gauge control module.

   NO 

   An open or poor connection in the B-CAN_H wire between the keyless access/TPMS control unit and the gauge control module.