DTC B1931: Backup Control Unit No Response
| DTC Description | DTC |
|---|---|
| B1931: Backup Control Unit No Response |
DTC (Backup 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 .
- Problem verification
- 1. Clear the DTCs with the HDS.
- 2. Open the driver's window all the way down, and close all the doors, then turn the vehicle to the OFF (LOCK) mode.
- 3. Remove all the keyless remotes from inside the vehicle. Hold one keyless remote outside of the opened driver's window at least 8.0 in (20 cm) away from the vehicle.
- 4. With holding the keyless remote outside of the opened driver's window, press the power switch, and wait for 30 seconds. Repeat this procedure a total of 5 times.
- 5. 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.
- Connector check
- 1. Turn the vehicle to the OFF (LOCK) mode.
- 2. Check for loose connections in the power switch 10P connector.
Is the connection OK?
YES
Go to step 3.
NO
Repair the poor connection of power switch 10P connector, and then recheck the system.
- Backup control unit SS1 (+), SS2 (-) lines check
- 1. Disconnect the following connector.
KEYLESS ACCESS CONTROL UNIT CONNECTOR B (28P) - 2. Measure the voltage between test points 1 and 2.
Test condition Vehicle ON mode, press and hold the power switch Keyless access control unit connector B (28P): disconnected
Test circuit SS1(+), SS2 (-) Test point 1 Keyless access control unit connector B (28P) No. 12 (BLU) Test point 2 Keyless access control unit connector B (28P) No. 8 (GRN) Is there battery voltage?
YES
Go to step 5.
NO
Go to step 4.
- Power switch check
- 1. Turn the vehicle to the OFF (LOCK) mode.
- 2. Test the power switch.
Is the switch OK?
YES
Repair an open or high resistance in the wire.
NO
The SS1 (+) and SS2 (-) wires are OK. REPLACE THE POWER SWITCH .
- 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 (28P)POWER SWITCH 10P CONNECTOR - 3. Check for continuity between test points 1 and 2 individually.
Test condition Vehicle OFF (LOCK) mode Keyless access control unit connector B (28P): disconnected
Power switch 10P connector: disconnected
Test circuit DIN/DOUT Test point 1 Keyless access control unit connector B (28P) No. 24 (LT BLU) Test point 2 Body ground Test circuit DCK Test point 1 Keyless access control unit connector B (28P) No. 23 (WHT) 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 6.
- 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 (28P): disconnected
Power switch 10P connector: disconnected
Test circuit DIN/DOUT Test point 1 Keyless access control unit connector B (28P) No. 24 (LT BLU) Test point 2 Power switch 10P connector No. 9 (LT BLU) Test circuit DCK Test point 1 Keyless access control unit connector B (28P) No. 23 (WHT) Test point 2 Power switch 10P connector No. 10 (WHT) 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.
- 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 (28P)POWER SWITCH 10P CONNECTOR - 3. Check for continuity between test points 1 and 2.
Test condition Vehicle OFF (LOCK) mode Keyless access control unit connector B (28P): disconnected
Test circuit SS SW VCONT Test point 1 Keyless access control unit connector B (28P) No. 25 (PUR) 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 8.
- 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 (28P): disconnected
Power switch 10P connector: disconnected
Test circuit SS SW VCONT Test point 1 Keyless access control unit connector B (28P) No. 25 (PUR) Test point 2 Power switch 10P connector No. 7 (PUR) Is there continuity?
YES
REPLACE THE KEYLESS ACCESS CONTROL UNIT .
NO
Repair an open or high resistance in the wire.