DTC Troubleshooting: U1281 (I-A3), U1281 (91), U128D (I-A2), U128D (83), U1290 (I-A6), U1290 (8F)
DTC U1281 or DTC screen I-A3 or DTC indicator 91: Climate Control Unit Lost Communication with MICU (body control module)
DTC U128D or DTC screen I-A2: Climate Control Unit Lost communication with gauge control module
DTC U128D or DTC indicator 83: Climate Control Unit Lost communication with gauge control module (VSP message)
DTC U1290 or DTC screen I-A6 or DTC indicator 8F: Climate Control Unit Lost Communication With Seat Heater Control Unit (front)
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 climate control unit.
Refer to the DTC shown on the display, then inspect the connectors and terminals based on the instructions.

DTC Description
DTC
U1281 Climate Control Unit Lost Communication with MICU (body control module)
  
U128D Climate Control Unit Lost communication with gauge control module
  
U1290 Climate Control Unit Lost Communication With Seat Heater Control Unit (front)
  

1.
Problem verification:

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.
Do the Self-Diagnostic Function with the climate control unit.

?5.
Check for DTCs.
DTC Description
DTC
U1281 Climate Control Unit Lost Communication with MICU (body control module)
  
U128D Climate Control Unit Lost communication with gauge control module
  
U1290 Climate Control Unit Lost Communication With Seat Heater Control Unit
  

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 climate control unit.?
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.
Climate control unit connector A (32P)

?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)
U1290
Front seat heater control unit 24P connector

?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
Climate control unit connector A (32P): 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
Climate control unit connector A (32P)
No. 25
Body control module connector B (36P)
No. 20
B-CAN_L
No. 8
No. 21
U128D
B-CAN_H
Climate control unit connector A (32P)
No. 25
Gauge control module connector A (32P)
No. 30
B-CAN_L
No. 8
No. 31
U1290
B-CAN_H
Climate control unit connector A (32P)
No. 25
Front seat heater control unit 24P connector
No. 10
B-CAN_L
No. 8
No. 9

Is there continuity?

     
YES
     
     
     
The B-CAN_H wire and B-CAN_L wire is 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.
U1290
Substitute a known-good front seat heater control unit, then recheck. If DTC U1290 goes away after substitution, replace the original front seat heater control unit.
     
NO
     
     
     
Repair an open in the B-CAN_H wire and/or the B-CAN_L wire between the climate control unit and the transmitting control unit.?