DTC Troubleshooting: B1931 - Honda FIT GK 2014-2020

1.

Problem verification:

Problem verification

?1.	Turn the vehicle to the ON mode.

?2.	Clear the DTCs with the HDS.

?3.	Open the driver's window all the way down, and close all the doors, then turn the vehicle to the OFF (LOCK) mode.

?4.	Remove all the keyless remotes from inside the vehicle. Hold one keyless remote outside of the opened driver's window at least 20 cm (7.9 in) away from the vehicle.

?5.	With holding the keyless remote outside of the opened driver's window, press the engine start/stop switch, and wait for 30 seconds. Repeat this procedure a total of 5 times.

?6.

Check for DTCs with the HDS.

DTC Description	DTC
B1931 Backup Control Unit No Response

Is DTC B1931 indicated?


	YES

Go to step 2.


	NO

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

2.

Connector check:

Connector check

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

?2.	Check for loose connections in the engine start/stop switch 12P connector.

Is the connections OK?


	YES

Go to step 3.


	NO

Repair the poor connection of engine start/stop switch 12P connector, and then recheck the system.?

3.

Backup control unit SS1(+), SS2(-) lines check:

Backup control unit SS1(+), SS2(-) lines check

?1.

Disconnect the following connector.

Keyless access control unit connector B (36P)

?2.	Turn the vehicle to the ON mode, and keep pressing the engine start/stop switch.

?3.

Measure the voltage between test points 1 and 2.

Test condition	Vehicle ON mode Keyless access control unit connector B (36P): disconnected
Test point 1	Keyless access control unit connector B (36P) No. 10
Test point 2	Keyless access control unit connector B (36P) No. 11

Is there battery voltage when the engine start/stop switch is pressed?


	YES

Go to step 5.


	NO

Go to step 4.

4.

Engine start/stop switch check:

Engine start/stop switch check

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

?2.	Test the engine start/stop switch.

Is the engine start/stop switch OK?


	YES

Repair an open or high resistance in the SS1(+) and/or SS2(-) wire(s).?


	NO

The SS1(+) and SS2(-) wires are OK. Replace the engine start/stop switch.?

5.

Engine start/stop switch SS SW VCONT line check:

Engine start/stop switch SS SW VCONT line check

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

?2.

Reconnect the following connector.

Keyless access control unit connector B (36P)

?3.	Turn the vehicle to the ON mode.

?4.

Measure the voltage between test points 1 and 2.

Test condition	Vehicle ON mode
Test point 1	Engine start/stop switch 12P connector No. 12
Test point 2	Body ground

Is there battery voltage?


	YES

Go to step 6.


	NO

Go to step 8.

6.

Shorted wire check (DIN/DOUT, DCK lines):

Shorted wire check (DIN/DOUT, DCK lines)

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

?2.

Disconnect the following connectors.

Keyless access control unit connector B (36P)
Engine start/stop switch 12P connector

?3.

Check for continuity between test points 1 and 2 individually.

Test condition	Vehicle OFF (LOCK) mode Keyless access control unit connector B (36P): disconnected Engine start/stop switch 12P connector: disconnected
Test point 1	Keyless access control unit connector B (36P) No. 21
Test point 2	Body ground

Test point 1	Keyless access control unit connector B (36P) No. 20
Test point 2	Body ground

Is there continuity?


	YES

Repair a short to ground in the wire.?


	NO

The DIN/DOUT and DCK wires are not shorted. Go to step 7.

7.

Open wire check (DIN/DOUT, DCK lines):

Open wire check (DIN/DOUT, DCK lines)

?1.

Check for continuity between test points 1 and 2 respectively.

Test condition	Vehicle OFF (LOCK) mode Keyless access control unit connector B (36P): disconnected Engine start/stop switch 12P connector: disconnected
Test point 1	Keyless access control unit connector B (36P) No. 21
Test point 2	Engine start/stop switch 12P connector No. 9

Test point 1	Keyless access control unit connector B (36P) No. 20
Test point 2	Engine start/stop switch 12P connector No. 11

Is there continuity?


	YES

The DIN/DOUT and DCK wires are OK. Replace the keyless access control unit.?


	NO

Repair an open or high resistance in the wire.?

8.

Shorted wire check (SS SW VCONT line):

Shorted wire check (SS SW VCONT line)

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

?2.

Disconnect the following connectors.

Keyless access control unit connector B (36P)
Engine start/stop switch 12P connector

?3.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode Keyless access control unit connector B (36P): disconnected Engine start/stop switch 12P connector: disconnected
Test point 1	Keyless access control unit connector B (36P) No. 24
Test point 2	Body ground

Is there continuity?


	YES

Repair a short to ground in the wire.?


	NO

The SS SW VCONT wire is not shorted. Go to step 9.

9.

Open wire check (SS SW VCONT line):

Open wire check (SS SW VCONT line)

?1.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode Keyless access control unit connector B (36P): disconnected Engine start/stop switch 12P connector: disconnected
Test point 1	Keyless access control unit connector B (36P) No. 24
Test point 2	Engine start/stop switch 12P connector No. 2

Is there continuity?


	YES

Replace the keyless access control unit.?


	NO

Repair an open or high resistance in the wire.?