Fault code C1800 – a step-by-step guide to diagnosing and fixing it

Error code C1800 is displayed and the check engine light is on - what does this mean?

The DTC C1800 is recognized by the OBD/EOBD system and indicates a fault in the anti-lock braking system (ABS), specifically an interruption or defect in the ABS control unit or the corresponding wiring. This trouble code can have slightly different meanings for different manufacturers, but basically refers to the ABS electronics.

What causes can this error code have?

• Defective ABS control unit
• Damaged wiring to the ABS module
• Corroded or loose plug connections
• Defective ABS sensors
• Broken ground wire
• Power supply problems in the ABS system
• Defective ABS hydraulic unit
• Software error in the control unit

What symptoms occur in parallel with fault code C1800?

• ABS warning light: The ABS indicator light in the dashboard is permanently illuminated
• Brake problems: The anti-lock braking system is no longer working properly
• Longer braking distances: Wheels may lock up, especially on slippery surfaces
• ESP failure: Electronic stability programs may also be affected
• Diagnostic fault messages: Other related fault codes may occur

How to fix the problem of fault code C1800?

• The repair requires a systematic diagnosis of the ABS system and appropriate measures.
• Check and replace the ABS control unit: Diagnose the faulty control unit and replace it with a new or repaired module if necessary
• Check wiring and plug connections: Check all cable connections to the ABS system for damage, corrosion or loose contacts and repair them
• Test and replace ABS sensors: Check the wheel speed sensors for function and replace defective sensors
• Check the power supply: Measure the power supply to the ABS system and check fuses and relays
• Carry out a software update: If there are known software errors, update the control unit with the latest firmware