DTC U128D: Power 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 - Refer to: Body Electrical Troubleshooting - B-CAN System Diagnosis Test Mode A - Initial Communication and DTC ChecksBody 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 CommunicatingBody Electrical Troubleshooting - B-CAN System Diagnosis Test Mode C - No DTCs and Output Won't Shut OFFBody Electrical Troubleshooting - B-CAN System Diagnosis Test Mode D - No DTCs and Output Won't Turn ON .

• 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 Power 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 GAUGES from the BODY ELECTRICAL SYSTEM SELECT menu, and then select DATA LIST.

  Does the DATA LIST appear?

  YES 

  Go to step 6.

  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.

  NO 

  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).

  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 connector.

  Keyless access control unit connector B (28P) Gauge control module connector A (32P)

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

  Test condition	Vehicle OFF (LOCK) mode Gauge control module connector A (32P): disconnected Keyless access control unit connector B (28P): disconnected
  Test point 1	Gauge control module connector A (32P) No. 30
  Test point 2	Keyless access control unit connector B (28P) No. 6

  Is there continuity?

  YES 

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

  NO 

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

• 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 connector A (32P): disconnected Keyless access control unit connector B (28P): disconnected
  Test point 1	Gauge control module connector A (32P) No. 31
  Test point 2	Keyless access control unit connector B (28P) No. 7

  Is there continuity?

  YES 

  The B-CAN_L wire is OK. Replace the gauge control module .

  NO 

  An open or poor connection in the B-CAN_L wire between the gauge control module and the power tailgate control unit.