Safety Warning
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.
Diagnostic Test
- CHECK FOR DTC C1090-ABS BRAKE LAMP CONTROL CIRCUIT LOW NOTE:
This DTC must be active for the results of this test to be valid.
- Turn the ignition on.
- With the scan tool, record and erase DTCs.
- Start Engine.
- Apply brake pedal firmly with at least 80 bar (1160 psi.).
- With the scan tool, read DTCs.
Does the scan tool display: C1090-ABS BRAKE LAMP CONTROL CIRCUIT LOW?
Yes
- Go To 2
No
- Perform the ABS-INTERMITTENT CONDITION TEST. Refer to STANDARD PROCEDURE .
- CHECK CONNECTOR/TERMINAL FOR DAMAGE NOTE:
Check all terminals for broken, bent, pushed out, or corroded terminals.
- Turn the ignition off.
- Inspect the ABS Module harness connector and the Brake Lamp Activation Relay harness connector.
Is the ABS Module or any of the connectors/terminals damaged?
Yes
- Repair as necessary.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
No
- Go To 3
- CHECK (B401) BRAKE LAMP ACTIVATION RELAY CONTROL SHORTED TO GROUND Fig 1: Probing Brake Lamp Activation Relay Control Circuit Using 12-Volt Test Light Connected To Ground
Courtesy of CHRYSLER GROUP, LLC
- Turn the ignition off.
- Disconnect the ABS Module harness connector.
- Start the engine.
- Using a 12-volt test light connected to ground, probe the (B401) Brake Lamp Activation Relay Control Circuit at the ABS Module harness connector.
Does the test light illuminate brightly?
Yes
- Replace the Anti-Lock Brake System (ABS) Module in accordance with the service information.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
No
- Go To 4
- CHECK (F941) FUSED RUN/START RELAY OUTPUT
Courtesy of CHRYSLER GROUP, LLC
- Turn the ignition off.
- Disconnect the Brake Lamp Activation Relay.
- Start the engine.
- Using a 12-volt test light connected to ground, probe the (F941) Fused Run/Start Relay Output Circuit at the Brake Lamp Activation Relay harness connector.
Does the test light illuminate brightly?
Yes
- Go To 5
No
- Check for open Fuse, if ok repair open or short to ground in the (F941) Fused Run/Start Relay Output Circuit.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
- BRAKE LAMP ACTIVATION RELAY
Courtesy of CHRYSLER GROUP, LLC
- Turn the ignition off.
- Measure the resistance of the (B401) Brake Lamp Activation Relay Control Circuit between the Brake Lamp Activation relay and the ABS Module harness connector.
Is the resistance 5 Ohms ?
Yes
- Replace the Brake Lamp Activation Relay in accordance with the Service Information.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
No
- Repair open in the (B401) Brake Lamp Activation Relay Control circuit.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.