DTC : U1281, U128D (Automatic Lighting Control Unit) (2016 2017 2018)

DTC U1281  : Auto light control unit lost communication with MICU

DTC U128D  : Auto light control unit lost communication with gauge control module

NOTE: 

• 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 (Automatic Lighting Control Unit)

NOTE:  If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A - Refer to:

Body Electrical Troubleshooting - B-CAN System Diagnosis Test Mode A - Initial Communication and DTC Checks .

1. Problem verification

   -1. Clear the DTCs with the HDS.

   Clear DTCs

   - 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
   U1281 Auto light control unit lost communication with MICU
   U128D Auto light control unit lost communication with gauge control module

   Are DTC U1281 or U128D indicated?

   YES 

   Go to step 2.

   NO 

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

2. Open wire check (B-CAN_H, 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 connectors.

   Gauge control module 32P connector

   Under-dash fuse/relay box connector M (12P)

   - 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 as specified in the table while in the vehicle OFF (LOCK) mode.

   DTC	CIRCUIT NAME	RECEIVING CONTROL UNIT	TRANSMITTING CONTROL UNIT
   U1281 Auto light control unit lost communication with MICU	B-CAN_H	Automatic Lighting Control Unit-Sensor 5P Connector No. 1	Under-Dash Fuse/Relay Box Connector M (12P) No. 7
   	B-CAN_L	Automatic Lighting Control Unit-Sensor 5P Connector No. 2	Under-Dash Fuse/Relay Box Connector M (12P) No. 1
   U128D Auto light control unit lost communication with gauge control module	B-CAN_H	Automatic Lighting Control Unit-Sensor 5P Connector No. 1	Gauge control module 32P connector No. 26 - Refer to: Gauge Control Module Connector for Inputs and Outputs (2016 2017 2018) .
   	B-CAN_L	Automatic Lighting Control Unit-Sensor 5P Connector No. 2	Gauge control module 32P connector No. 27 - Refer to: Gauge Control Module Connector for Inputs and Outputs (2016 2017 2018) .

   Is there continuity?

   YES 

   The B-CAN_L to B-CAN_H wire is OK. Go to step 3.

   NO 

   Repair an open or high resistance in the B-CAN_H and/or B-CAN_L wire (S) between the receiving control unit and the transmitting control unit.

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

   -1. Reconnect all connectors.

   - 2. Turn the vehicle to the ON mode.

   - 3. Clear the DTCs with the HDS.

   Clear DTCs

   - 4. Check for DTCs with the HDS.

   DTC Description	DTC
   U1281 Auto light control unit lost communication with MICU
   U128D Auto light control unit lost communication with gauge control module

   Are DTC U1281 and U128D indicated?

   YES 

   Check for loose terminals and poor connections in the automatic lighting control unit-sensor connector. Check is OK, replace the Automatic Lighting Control Unit-Sensor - Removal and Installation .

   NO 

   The automatic lighting control unit-sensor is OK at this time. Update or replace the transmitting control unit. (Refer to the DTC code shown on the display, and then update or replace the control unit based on the instructions in the table below.)

   DTC	TRANSMITTING CONTROL UNIT
   U1281 Auto light control unit lost communication with MICU	Update or replace the MICU
   U128D Auto light control unit lost communication with gauge control unit	Replace the gauge control module