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 .
• Refer to the DTC code shown on the display, and then inspect the connectors and terminals based on the instructions in the table below.
• The DTC may be stored due to the grounding failure or the power source failure at the transmitting control unit (the grounding inspection and the power source inspection on each control unit are required prior to this checking process).

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
   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.

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 B (36P)

   -3. Disconnect the transmitting control unit connector(s).

   Refer to the DTC shown on the display, then disconnect the connector(s) based on the instructions (see table).

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

   -4. Measure the resistance 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 B (36P): 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 B (36P)	No. 20	Gauge control module connector A (32P)	No. 30
   	B-CAN_L		No. 21		No. 31
   U1291	B-CAN_H	Body control module connector B (36P)	No. 20	Relay control module connector A (6P)	No. 2
   	B-CAN_L		No. 21		No. 3

   Is there 1.0 Ω or less?

   YES 

   The B-CAN_H wire and the B-CAN_L wire are OK. Refer to the DTC shown on the display, then replace the control unit based on the instructions (see table).

   DTC	Operation for transmitting control unit
   U128D	Gauge control module
   U1291	Relay control module

   NO 

   Repair an open in the B-CAN_H wire and/or the B-CAN_L wire.