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DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC B2A10-14 (Adaptive Cruise Control Unit) (2014 2015 2016 2017)
DTC B2A10-14 : Brake Light Relay Circuit Malfunction
| DTC Description | DTC | Freeze Frame |
|---|---|---|
| B2A10-14 Brake Light Relay Circuit Malfunction |
DTC (ACC)
- DTC check 1
-1. Turn the vehicle to the ON mode.
-2. Clear the DTC with the HDS.
-3. Turn the vehicle to the OFF (LOCK) mode, then the ON mode.
-4. Check for DTCs with the HDS.
DTC Description DTC Freeze Frame B2A10-14 Brake Light Relay Circuit Malfunction Is DTC B2A10-14 indicated?
YES
Go to step 17.
NO
Go to step 2.
- DTC check 2
-1. Turn the vehicle to the OFF (LOCK) mode, then the ON mode.
-2. Check for DTCs with the HDS when pressing the brake pedal.
DTC Description DTC Freeze Frame B2A10-14 Brake Light Relay Circuit Malfunction Is DTC B2A10-14 indicated?
YES
Go to step 3.
NO
Go to step 11.
- Brake light check
-1. Check the brake lights when pressing the brake pedal.
Do the brake lights come on?
YES
Go to step 4.
NO
Go to step 5.
- Open wire check (BRK DIAG line)
-1. Turn the vehicle to the OFF (LOCK) mode.
-2. Disconnect the following connector.
ACC unit 20P connector -3. Measure the voltage between test points 1 and 2.
Test condition Vehicle OFF (LOCK) mode ACC unit 20P connector: disconnected Test circuit BRK DIAG Test point 1 ACC unit 20P connector No. 8 (GRN) Test point 2 Body ground Is there battery voltage when the brake pedal is pressed?
YES
The BRK DIAG wire is OK. Go to step 19.
NO
Repair an open in the wire between the ACC unit and the branch of the BRK DIAG line.
- Brake pedal position switch check 1
-1. Start the engine.
-2. Check the parameter (s) below with the HDS.
Signal Current conditions Values Unit BRAKE SW (N.O.) Does the indication show ON when the brake pedal is pressed, and show OFF when the brake pedal is released?
YES
Go to step 6.
NO
Go to step 8.
- Brake light relay check
-1. Turn the vehicle to the OFF (LOCK) mode.
-2. Check the brake light relay .
Is the brake light relay OK?
YES
Go to step 7.
NO
Replace the brake light relay.
- Open wire check (BRK DIAG line)
-1. Disconnect the following connectors.
Brake light relay 5P socket (if connected) Taillight 4P connector -2. Check for continuity between test points 1 and 2.
Test condition Vehicle OFF (LOCK) mode Taillight 4P connector: disconnected Brake light relay 5P socket: disconnected Test circuit BRK DIAG Test point 1 Taillight 4P connector No. 3 (GRN) Test point 2 Brake light relay 5P socket No. 1 (GRN) Is there continuity?
YES
Repair an open in the wire between the brake light relay and the brake pedal position switch.
NO
Repair an open in the wire between the brake light relay and the taillight.
- Fuse check
-1. Turn the vehicle to the OFF (LOCK) mode.
-2. Check the following fuse.
Fuse No. C19 (7.5 A) Location Under-hood fuse/relay box Is the fuse OK?
YES
The fuse is OK. Reinstall the fuse, then go to step 9.
NO
Replace the fuse. If the fuse blows again, repair the short to ground on the No. C19 (7.5 A) fuse circuit.
- Brake pedal position switch check 2
-1. Test the brake pedal position switch .
Is the brake pedal position switch OK?
YES
Go to step 10.
NO
- Open wire check (+B STOP line)
-1. Disconnect the following connector.
Brake pedal position switch 4P connector -2. Measure the voltage between test points 1 and 2.
Test condition Vehicle OFF (LOCK) mode Brake pedal position switch 4P connector: disconnected Test circuit +B STOP Test point 1 Brake pedal position switch 4P connector No. 2 (PUR) Test point 2 Body ground Is there battery voltage?
YES
Repair an open in the wire between the brake light relay and the brake pedal position switch.
NO
Repair an open in the wire between the No. C19 (7.5 A) fuse in the under-hood fuse/relay box and brake pedal position switch.
- Problem verification 1
-1. Do the BRAKE LIGHT RELAY function test with the HDS.
Brake Light Relay
Check for DTCs with the HDS.
DTC Description DTC Freeze Frame B2A10-14 Brake Light Relay Circuit Malfunction Is DTC B2A10-14 indicated?
YES
The failure is duplicated. Go to step 12.
NO
Intermittent failure, the system is OK at this time.
- Problem verification 2
-1. Do the BRAKE LIGHT RELAY function test with the HDS.
Brake Light Relay
Is there sound heard from the relay?
YES
Go to step 13.
NO
Go to step 14.
- Open wire check (+B STOP line) 2
-1. Turn the vehicle to the OFF (LOCK) mode.
-2. Disconnect the following connector.
Brake light relay 5P socket (if connected) -3. Measure the voltage between test points 1 and 2.
Test condition Vehicle OFF (LOCK) mode Brake light relay 5P socket: disconnected Test circuit +B STOP Test point 1 Brake light relay 5P socket No. 2 (PUR) Test point 2 Body ground Is there battery voltage?
YES
The +B STOP wire is OK. Replace the brake light relay.
NO
Repair an open in the wire between the No. C19 (7.5 A) fuse in the under-hood fuse/relay box and the brake light relay.
- Open wire check (IG1 DR2 line) 1
-1. Turn the vehicle to the OFF (LOCK) mode.
-2. Disconnect the following connector.
Brake light relay 5P socket (if connected) -3. Turn the vehicle to the ON mode.
-4. Measure the voltage between test points 1 and 2.
Test condition Vehicle ON mode Brake light relay 5P socket: disconnected Test circuit IG1 DR2 Test point 1 Brake light relay 5P socket No. 3 (WHT) Test point 2 Body ground Is there battery voltage?
YES
The IG1 DR2 wire is OK. Go to step 15.
NO
Repair an open in the wire between the brake light relay and the No. D24 (7.5 A) fuse in the driver's under-dash fuse/relay box.
- Brake light relay check 2
-1. Turn the vehicle to the OFF (LOCK) mode.
-2. Check the brake light relay.
Is the brake light relay OK?
YES
Go to step 16.
NO
Replace the brake light relay.
- Open wire check (BRK LAMP line)
-1. Turn the vehicle to the OFF (LOCK) mode.
-2. Disconnect the following connectors.
Brake light relay 5P socket (if connected) ACC unit 20P connector -3. Check for continuity between test points 1 and 2.
Test condition Vehicle OFF (LOCK) mode ACC unit 20P connector: disconnected Brake light relay 5P socket: disconnected Test circuit BRK LAMP Test point 1 ACC unit 20P connector No. 11 (GRY) Test point 2 Brake light relay 5P socket No. 5 (GRY) Is there continuity?
YES
The BRK LAMP wire is OK. Go to step 19.
NO
Repair an open in the wire between the ACC unit and the brake light relay.
- Brake light relay check 2
-1. Turn the vehicle to the OFF (LOCK) mode.
-2. Check the brake light relay .
Is the brake light relay OK?
YES
Go to step 18.
NO
Replace the brake light relay.
- Short wire check (BRK LAMP line)
-1. Disconnect the following connectors.
Brake light relay 5P socket (if connected) ACC unit 20P connector -2. Check for continuity between test points 1 and 2.
Test condition Vehicle OFF (LOCK) mode Brake light relay 5P socket: disconnected Test circuit BRK LAMP Test point 1 Brake light relay 5P socket No. 5 (GRY) Test point 2 Body ground Is there continuity?
YES
Repair a short to body ground between the ACC unit and the brake light relay.
NO
The BRK LAMP wire is OK. Go to step 19.
- ACC unit check (update)
-1. Reconnect the following connectors.
Brake light relay 5P socket (if disconnected) ACC unit 20P connector -2. Update the ACC unit if it does not have the latest software .
-3. Turn the vehicle to the OFF (LOCK) mode, then the ON mode.
-4. Check for DTCs with the HDS.
DTC Description DTC Freeze Frame Is DTC B2A10-14 indicated?
YES
Check for loose terminals in the ACC unit 20P connector. If the ACC unit was updated and the symptom/indication is still present, replace the ACC unit .
NO
Troubleshooting is complete. If any other DTCs are indicated, go to the indicated DTC's troubleshooting.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.