DTC Troubleshooting: B123F (A-A3), B123F (17) (2017 2018 2019)

DTC B123F or DTC screen A-A3 or DTC indicator 17  : Automatic lighting control unit/sunlight sensor error

DTCs (AC)

1. Problem verification

   -1. Clear the DTCs with the HDS.

   -2. Turn the vehicle to the OFF (LOCK) mode and then the ON mode.

   -3. Do the Self-Diagnostic Function with the HDS or the climate control unit .

   -4. Check for DTCs.

   DTC Description	DTC
   B123F Automatic lighting control unit/sunlight sensor error

   Is DTC B123F or Error on the DTC screen A-A3 (climate control panel without display) or 17 (climate control panel with display) indicated?

   YES 

   Go to step 2.

   NO 

   Intermittent failure, the system is OK at this time.

2. Equipment check 1

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

   -2. Confirm the vehicle have an automatic lighting system.

   Does the combination light switch have an AUTO position?

   YES 

   Go to step 3.

   NO 

   Go to step  4.

3. Equipment check 2

   -1. Confirm the vehicle have an automatic wiper system.

   Does the wiper/washer switch have an AUTO position?

   YES 

   Go to step 4.

   NO 

   Go to step  9.

4. Open wire check (TSUN line)

   -1. Disconnect the following connectors.

   Climate control unit connector A (32P)

   Sunlight sensor 2P connector

   -2. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector A (32P): disconnected
   	Sunlight sensor 2P connector: disconnected
   Test point 1	Climate control unit connector A (32P) No. 10
   Test point 2	Sunlight sensor 2P connector (female terminals) No. 2:

   Courtesy of HONDA, U.S.A., INC.

   Is there continuity?

   YES 

   The TSUN wire is not open. Go to step 5.

   NO 

   Repair an open in the TSUN wire.

5. Open wire check (SENSOR COM line)

   -1. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector A (32P): disconnected
   	Sunlight sensor 2P connector: disconnected
   Test point 1	Climate control unit connector A (32P) No. 12
   Test point 2	Sunlight sensor 2P connector (female terminals) No. 1:

   Courtesy of HONDA, U.S.A., INC.

   Is there continuity?

   YES 

   The SENSOR COM wire is OK. Go to step 6.

   NO 

   Repair an open in the SENSOR COM wire.

6. Shorted wire check (TSUN line)

   -1. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector A (32P): disconnected
   	Sunlight sensor 2P connector: disconnected
   Test point 1	Climate control unit connector A (32P) No. 10
   Test point 2	Body ground

   Is there continuity?

   YES 

   Repair a short to ground in the TSUN wire.

   NO 

   The TSUN wire is not shorted. Go to step 7.

7. Shorted wire check (TSUN line to SENSOR COM line)

   -1. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector A (32P): disconnected
   	Sunlight sensor 2P connector: disconnected
   Test point 1	Climate control unit connector A (32P) No. 10
   Test point 2	Climate control unit connector A (32P) No. 12

   Is there continuity?

   YES 

   Repair a short in the TSUN wire to SENSOR COM wire.

   NO 

   The TSUN wire and SENSOR COM wire are OK. Go to step 8.

8. Sunlight sensor check

   -1. Reconnect the following connectors.

   Climate control unit connector A (32P)

   Sunlight sensor 2P connector

   -2. Test the sunlight sensor .

   Is the sunlight sensor OK?

   YES 

   Replace the climate control unit .

   NO 

   Replace the sunlight sensor .

9. Fuse check:
   NOTE:

   Check for DTCs. If a DTC U1280 or Error on the DTC screen I-A1 (climate control panel without display) or 80 (climate control panel with display) indicated, troubleshoot the DTC first.

   -1. Check the following fuse.

   Fuse	No. A18 (10 A)
   Location	Under-hood fuse/relay box

   Is the fuse OK?

   YES 

   Go to step 10.

   NO 

   Replace the fuse, and recheck. If the fuse blows again, repair a short in the No. A18 (10 A) fuse circuit.

10. Determine possible failure area (B-CAN lines, others)

    -1. Disconnect the following connector.

    Automatic lighting control unit-sensor 5P connector

    -2. Measure the voltage between test points 1 and 2.

    Test condition	Vehicle OFF (LOCK) mode
    	Automatic lighting control unit-sensor 5P connector: disconnected
    Test point 1	Automatic lighting control unit-sensor 5P connector No. 3

    Test point 2

    Automatic lighting control unit-sensor 5P connector No. 4

    Is there battery voltage?

    YES 

    Go to step 11.

    NO 

    Go to step  14.

11. Open wire check (B-CAN_H line)

    -1. Disconnect the following connector.

    Climate control unit connector A (32P)

    -2. Check for continuity between test points 1 and 2.

    Test condition	Vehicle OFF (LOCK) mode
    	Automatic lighting control unit-sensor 5P connector: disconnected
    	Climate control unit connector A (32P): disconnected
    Test point 1	Automatic lighting control unit-sensor 5P connector No. 1
    Test point 2	Climate control unit connector A (32P) No. 25

    Is there continuity?

    YES 

    The B-CAN_H wire is OK. Go to step 12.

    NO 

    Repair an open in the B-CAN_H wire.

12. Open wire check (B-CAN_L line)

    -1. Check for continuity between test points 1 and 2.

    Test condition	Vehicle OFF (LOCK) mode
    	Automatic lighting control unit-sensor 5P connector: disconnected
    	Climate control unit connector A (32P): disconnected
    Test point 1	Automatic lighting control unit-sensor 5P connector No. 2
    Test point 2	Climate control unit connector A (32P) No. 8

    Is there continuity?

    YES 

    The B-CAN_L wire is OK. Go to step 13.

    NO 

    Repair an open in the B-CAN_L wire.

13. DTC check

    -1. Reconnect the following connectors.

    Automatic lighting control unit-sensor 5P connector

    Climate control unit connector A (32P)

    -2. Clear the DTC with the HDS.

    -3. Turn the vehicle to the OFF (LOCK) mode then the ON mode.

    -4. Wait for at least 8 seconds.

    -5. Do the Self-Diagnostic Function with the climate control unit .

    -6. Check for DTCs.

    DTC Description	DTC
    B123F Automatic lighting control unit/sunlight sensor error
    U128D Climate Control Unit Lost communication with gauge control module

    Is DTC B123F or Error on the DTC screen A-A3 (climate control panel without display) or 17 (climate control panel with display) and DTC U128D or Error on the DTC screen I-A2 (climate control panel without display) or 83 (climate control panel with display) indicated?

    YES 

    Replace the climate control unit .

    NO 

    Replace the automatic lighting control unit-sensor .

14. Open wire check (+B BACK UP line)

    -1. Measure the voltage between test points 1 and 2.

    Test condition	Vehicle OFF (LOCK) mode
    	Automatic lighting control unit-sensor 5P connector: disconnected
    Test point 1	Automatic lighting control unit-sensor 5P connector No. 4
    Test point 2	Body ground

    Is there battery voltage?

    YES 

    Check for an open in the GND wire. If the wire is OK, check for poor ground at G402.

    NO 

    Repair an open in the +B BACK UP wire.