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 the DTCs.
- Start engine.
- Apply brake pedal firmly with at least 80 bar (1160 psi.).
- With the scan tool, read the DTCs.
Does the scan tool display: C1090-ABS BRAKE LAMP CONTROL CIRCUIT LOW?
Yes
- Go To 2
No
- Perform the ABS INTERMITTENT CONDITION diagnostic procedure. 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 Anti-Lock Brake Module harness connector and the Brake Lamp Activation Relay harness connector.
Is the ABM 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 (B122) BRAKE LAMP ACTIVATION RELAY CONTROL SHORTED TO GROUND
Courtesy of CHRYSLER GROUP, LLC
- Turn the ignition off.
- Disconnect the ABM.
- Start the engine.
- Using a 12-volt test light connected to ground, probe the (B122) Brake Lamp Activation Relay Control Circuit at the ABM harness connector.
Does the test light illuminate?
Yes
- Replace the ABM in accordance with the Service Iinformation.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
No
- Go To 4
- CHECK (A924) FUSED B+
- Turn the ignition off.
- Disconnect the Brake Lamp Activation Relay.
- Start the engine.
- Using a 12-volt test light connected to ground, probe the (A924) Fused B+ 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 okay repair open or short to ground in the (A924) Fused B+ Circuit or short to ground in (B122) Brake Lamp Activation Relay Control circuit.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
- BRAKE LAMP ACTIVATION RELAY Fig 3: Measuring Resistance Of Brake Lamp Activation Relay Control Circuit Between Brake Lamp Activation Relay And ABM
Courtesy of CHRYSLER GROUP, LLC
- Turn the ignition off.
- Measure the resistance of the (B122) Brake Lamp Activation Relay Control Circuit between the Brake Lamp Activation relay and the ABM.
Is the resistance below 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 (B122) Brake Lamp Activation Relay Control circuit.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
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.