Fault code C1201 – a step-by-step guide to diagnosing and fixing it

Error code C1201 is displayed and the check engine light is on - what does this mean?

The DTC C1201 is recognized by the OBD/EOBD system and indicates an error in the ABS control module or in the communication between different vehicle control units. This fault code mainly affects the anti-lock braking system (ABS) and can have different specific meanings for different manufacturers, especially Toyota, Lexus and other Asian brands.

What causes can this error code have?

• Defective ABS control unit
• Interrupted power supply to the ABS module
• Damaged cable connections in the ABS system
• Faulty CAN bus communication
• Defective ABS sensors on the wheels
• Corroded or loose plug connections
• Weak or defective vehicle battery
• Damaged fuses in the ABS circuit
• Software error in the control unit
• Mechanical damage to the ABS hydraulic block

What symptoms occur in parallel with fault code C1201?

• ABS warning light: The ABS indicator light is permanently illuminated in the dashboard
• Loss of ABS function: The anti-lock braking system no longer works properly
• Starting problems: The vehicle may have starting difficulties
• Other warning lights: Additional indicator lights such as ESP or traction control may be activated
• Communication errors: Diagnostic devices cannot communicate with all control units
• Unusual brake noises: Clicking or buzzing noises when braking

How to fix the problem of trouble code C1201?

• Repairing trouble code C1201 requires a systematic approach to identify the exact cause.
• Battery check and replacement: Check the vehicle battery for sufficient voltage (at least 12.6V) and replace it if necessary, as weak batteries often cause C1201 codes
• Check fuses: Check all ABS-related fuses in the engine compartment and interior and replace blown fuses
• Inspect wiring connections: Inspect all cable connections to the ABS control unit for corrosion, damage or loose connections and repair them
• Test ABS sensors: Measure the resistance of all wheel speed sensors and replace defective sensors according to the manufacturer's specifications
• Perform a control unit reset: Clear the fault code with an OBD scanner and perform a test drive to see if the code reoccurs
• Professional diagnosis: If problems persist, have a comprehensive system diagnosis carried out at a specialist workshop, as the ABS control unit may need to be replaced