DTC Troubleshooting: B123F (17) - Honda FIT GK 2014-2020

1.

Problem verification:

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 DTC indicator 17 indicated?


	YES

The failure is duplicated. Go to step 2.


	NO

Intermittent failure, the system is OK at this time.?

2.

Fuse check:

Fuse check

NOTE: Check for DTCs. If a DTC U1280 or DTC indicator 80 indicated, troubleshoot the DTC first.

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

?2.

Check the following fuse.

Fuse

No. B29

Is the fuse OK?


	YES

Go to step 3.


	NO

Replace the fuse, and recheck. If the fuse blows again, repair a short in the No. B29 fuse circuit.?

3.

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

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
Test condition	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 4.


	NO

Go to step 7.

4.

Open wire check (B-CAN_H line):

Open wire check (B-CAN_H line)

?1.

Disconnect the following connector.

Climate control unit 32P connector

?2.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	Climate control unit 32P connector: disconnected
	Automatic lighting control unit-sensor 5P connector: disconnected
Test point 1	Climate control unit 32P connector No. 19
Test point 2	Automatic lighting control unit-sensor 5P connector No. 1

Is there continuity?


	YES

The B-CAN_H wire is OK. Go to step 5.


	NO

Repair an open in the B-CAN_H wire.?

5.

Open wire check (B-CAN_L line):

Open wire check (B-CAN_L line)

?1.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	Climate control unit 32P connector: disconnected
	Automatic lighting control unit-sensor 5P connector: disconnected
Test point 1	Climate control unit 32P connector No. 21
Test point 2	Automatic lighting control unit-sensor 5P connector No. 2

Is there continuity?


	YES

The B-CAN_L wire is OK. Go to step 6.


	NO

Repair an open in the B-CAN_L wire.?

6.

DTC check:

DTC check

?1.

Reconnect the following connectors.

Climate control unit 32P connector

Automatic lighting control unit-sensor 5P connector

?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 8 seconds.

?5.	Do the Self-Diagnostic Function with the HDS or 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 DTC indicator 17 and U128D or DTC indicator 81, 82, or 83 indicated?


	YES

Replace the climate control unit.?


	NO

Replace the automatic lighting control unit-sensor.?

7.

Open wire check (+B BACK UP line):

Open wire check (+B BACK UP line)

?1.

Measure the voltage between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
Test condition	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 between the automatic lighting control unit-sensor and body ground. If the wire is OK, check for poor ground at G403.?


	NO

Repair an open in the +B BACK UP wire.?