DTC U128D, U1291 (Body Control Module)

DTC U128D  : BCM Lost Communication With Gauge Control Module

DTC U1291  : BCM Lost Communication With Relay Control Module

NOTE: 

• If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A .
• According to the detected DTC (s), check for the power circuit and the ground circuit of the control unit which cannot communicate with the body control module.
• Refer to the DTC shown on the display, then inspect the connectors and terminals based on the instructions.

DTC (Body Control Module)

1. Problem verification

   -1. Clear the DTC 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 BCM lost communication with gauge control module

   DTC Description	DTC
   U1291 BCM lost communication with relay control module

   Are any DTCs indicated?

   YES 

   Go to step 2.

   NO 

   Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the transmitting control units and the body control module.

2. Open wire check (B-CAN_H line, B-CAN_L line)

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

   -2. Disconnect the receiving control unit connector.

   Body control module connector A (66P)

   -3. According to the detected DTC on the following table, disconnect the transmitting control unit connector (s).

   DTC	Connector
   U128D	Gauge control module connector A (32P)
   U1291	Relay control module connector A (6P)

   -4. Check for continuity between the receiving control unit and the transmitting control unit on the B-CAN_H circuit and the B-CAN_L circuit.

   Test condition

   Vehicle OFF (LOCK) mode Body control module connector A (66P): disconnected Transmitting control unit connector (s) for indicated DTCs: disconnected

   DTC	Circuit name	Receiving control unit		Transmitting control unit
   		Connector	Terminal	Connector	Terminal
   U128D	B-CAN_H	Body control module connector A (66P)	No. 54	Gauge control module connector A (32P)	No. 22
   	B-CAN_L		No. 55		No. 23
   U1291	B-CAN_H	Body control module connector A (66P)	No. 54	Relay control module connector A (6P)	No. 2
   	B-CAN_L		No. 55		No. 3

   Is there continuity?

   YES 

   The B-CAN_H wire and the B-CAN_L wire are OK. Go to step 3.

   NO 

   Repair an open in the B-CAN_H wire and/or the B-CAN_L wire between the body control module and the transmitting control unit.

3. Determine possible failure area (the receiving control unit or the transmitting control unit)

   -1. Reconnect all the connectors.

   -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 the DTCs with the HDS.

   DTC Description	DTC
   U128D BCM lost communication with gauge control module
   U1291 BCM lost communication with relay control module

   Are both DTCs indicated?

   YES 

   Check for loose terminals and poor connections in the body control module connectors. If they are OK, replace the body control module .

   NO 

   The body control module is OK at this time. According to the detected DTC on the following table, substitute or replace the control unit based on the instructions (see table).

   DTC	Operation for transmitting control unit
   U128D	Substitute a known-good gauge control module , then recheck. If DTC U128D goes away after substitution, replace the original gauge control module .
   U1291	Substitute a known-good relay control module , then recheck. If DTC U1291 goes away after substitution, replace the original relay control module .