DTC Troubleshooting: B1931
DTC B1931: Backup Control Unit No Response
DTC Description
DTC
B1931 Backup Control Unit No Response
 

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

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
Test point 2

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.

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
Test point 2
Body ground

Test point 1
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
Test point 2
Engine start/stop switch 12P connector No. 9

Test point 1
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
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
Test point 2
Engine start/stop switch 12P connector No. 2


Is there continuity?

     
YES
     
     
     
     
NO
     
     
     
Repair an open or high resistance in the wire.?