DTC U128D (HVAC Control Unit)

DTC U128D  : Climate Control Unit Lost communication with gauge control module (HVAC control unit)

DTCs (AC)

1. Problem verification

   -1. Clear the DTC with the HDS.

   -2. Turn the vehicle to the OFF (LOCK) mode, then the ON mode.

   -3. Wait for at least 6 seconds.

   -4. Do the Self-Diagnostic Function with the HDS or the HVAC control unit .

   -5. Check for DTCs.

   DTC Description	DTC
   U128D Climate Control Unit Lost communication with gauge control module (HVAC control unit)

   Is DTC U128D indicated?

   YES 

   Go to step 2.

   NO 

   Intermittent failure, the system is OK at this time. Check for loose wires or poor connections.

2. Determine possible failure area (gauge control module power and ground, B-CAN lines)

   -1. Select Gauges from the Body Electrical System Select menu, then select Data List.

   Does the Data List appear?

   YES 

   Go to step 3.

   NO 

   Go to step  5.

3. Open wire check (B-CAN_H line)

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

   -2. Disconnect the following connectors.

   Gauge control module 32P connector

   HVAC control unit connector A (32P)

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

   Test condition	Vehicle OFF (LOCK) mode
   	Gauge control module 32P connector: disconnected
   	HVAC control unit connector A (32P): disconnected
   Test point 1	Gauge control module 32P connector No. 26
   Test point 2	HVAC control unit connector A (32P) No. 23

   Is there continuity?

   YES 

   The B-CAN_H wire is OK. Go to step 4.

   NO 

   Repair an open in the wire between the HVAC control unit and the gauge control module.

4. 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
   	HVAC control unit connector A (32P): disconnected
   Test point 1	Gauge control module 32P connector No. 27
   Test point 2	HVAC control unit connector A (32P) No. 24

   Is there continuity?

   YES 

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

   NO 

   Repair an open in the wire between the HVAC control unit and the gauge control module.

5. Fuse check

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

   -2. Check the following fuse.

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

   Is the fuse OK?

   YES 

   Go to step 6.

   NO 

   Replace the fuse, and recheck. If the fuse blow again, repair a short in the No. A26 (10 A) fuse circuit.

6. Open wire check (+B BACKUP line)

   -1. Disconnect the following connector.

   Gauge control module 32P connector

   -2. 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
   Test point 2	Body ground

   Is there battery voltage?

   YES 

   Check for an open in the wire(s) between the gauge control module and body ground. If the wire(s) is OK, check for poor ground at G401.

   NO 

   Repair an open in the wire between the No. A26 (10 A) fuse in the under-hood fuse/relay box and the gauge control module.