DTC Troubleshooting: U1281, U128D
DTC U1281: Auto Light Control Unit Lost Communication with MICU (Body Control Module)
DTC U128D: Auto Light Control Unit Lost Communication with Gauge Control Module
NOTE:
According to the detected DTC(s), check for the power circuit and the ground circuit of the control unit which cannot communicate with the automatic lighting control unit-sensor.
Refer to the DTC shown on the display, then inspect the connectors and terminals based on the instructions.
If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A.

DTC Description
DTC
U1281 Auto Light Control Unit Lost Communication with MICU (Body Control Module)
  
U128D Auto Light Control Unit Lost Communication with Gauge Control Module
  

1.
Problem verification:

Problem verification
?1.
Turn the vehicle to the ON mode.

?2.
Clear the DTC 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 for DTCs with the HDS.
DTC Description
DTC
U1281 Auto Light Control Unit Lost Communication with MICU (Body Control Module)
  
U128D Auto Light Control Unit Lost Communication with Gauge 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 automatic lighting control unit-sensor.?
2.
Open wire check (B-CAN_H line, B-CAN_L line):

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.
Automatic lighting control unit-sensor 5P connector

?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
U1281
Body control module connector B (36P)
U128D
Gauge control module connector A (32P)

?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
Automatic lighting control unit-sensor 5P connector: disconnected
Transmitting control unit connector(s) for indicated DTCs: disconnected

DTC
Circuit name
Receiving control unit
Transmitting control unit
Connector
Terminal
Connector
Terminal
U1281
B-CAN_H
Automatic lighting control unit-sensor 5P connector
No. 1
Body control module connector B (36P)
No. 20
B-CAN_L
No. 2
No. 21
U128D
B-CAN_H
Automatic lighting control unit-sensor 5P connector
No. 1
Gauge control module connector A (32P)
No. 30
B-CAN_L
No. 2
No. 31

Is there continuity?

     
YES
     
     
     
The B-CAN_H wire and the B-CAN_L wire are OK.
Refer to the DTC shown on the display, then substitute or replace the control unit based on the instructions (see table).?
DTC
Operation for transmitting control unit
U1281
Substitute a known-good body control module, then recheck. If DTC U1281 goes away after substitution, replace the original body control module.
U128D
Substitute a known-good gauge control module, then recheck. If DTC U128D goes away after substitution, replace the original gauge control module.
     
NO
     
     
     
Repair an open in the B-CAN_H wire and/or the B-CAN_L wire between the automatic lighting control unit-sensor and the transmitting control unit.?