C0110 – Pump Motor Circuit indicates that the ABS/ESC control module has detected an electrical fault in the hydraulic pump motor circuit. This pump is essential for generating brake pressure during ABS activation and stability control events. When the circuit fails, the system may lose its ability to modulate brake pressure, resulting in warning lights and reduced stability control. This guide explains what C0110 means, common symptoms, causes, how to diagnose it, and the most effective fixes.
What Does C0110 Mean?
C0110 is a chassis-related OBD-II fault code set when the ABS module senses an abnormal voltage, open circuit, short, or high resistance in the pump motor circuit. The ABS system relies on a high-pressure electric pump to control hydraulic pressure during wheel-lock prevention and stability control events. Any interruption in power, ground, or motor operation results in reduced braking assistance under slippery conditions.
This failure may stem from a bad pump motor, corroded ground, blown fuse, internal ABS module failure, or wiring issues leading to inconsistent current flow. Because the pump only operates during ABS activity, the code may appear intermittently before becoming permanent.
Quick Reference
- OBD-II Family: C-Code (Chassis)
- Scope: Generic
- System: ABS / ESC Hydraulic Pump
- Difficulty Level: Moderate
- Estimated Repair Cost: €120–€900+
- Last Updated: 22 November 2025
Real-World Example / Field Notes
A sedan arrived with ABS and traction-control lights on. The pump motor wasn’t running during ABS self-test. Testing revealed a blown ABS pump fuse caused by an internal short in the pump motor. Replacing the ABS pump assembly fixed the problem permanently.
Another case involved an SUV where C0110 appeared intermittently. The pump ground strap near the frame rail was heavily corroded, causing high resistance and sporadic pump activation. Cleaning the ground surface and installing a new strap restored full ABS function.
Symptoms of C0110 – Pump Motor Circuit
- ABS warning light: Pump unable to build hydraulic pressure.
- Traction control or ESC light: Stability functions disabled.
- Longer stopping distances: No ABS modulation.
- Poor braking on slippery roads: Wheels may lock easily.
- No pump sound: Pump motor fails to activate during key-on self-test.
- Brake pedal pulsation (rare): Inconsistent pressure build-up.
Common Causes of C0110
Most Common Causes
- Failed ABS pump motor
- Corroded or loose pump motor ground connection
- Blown ABS pump fuse or relay failure
- Open or shorted wiring between pump and ABS module
- Internal ABS module circuitry failure
Less Common Causes
- Low system voltage causing pump underperformance
- Pump relay sticking or overheating
- Moisture intrusion in ABS pump assembly
- Corroded pump electrical connector pins
- Vehicle frame rust causing high resistance at grounding points
Diagnosis: Step-by-Step Guide
Diagnosing C0110 requires checking electrical power and ground integrity, verifying pump operation, and inspecting the ABS module’s control output.
Tools You’ll Need
Advanced scan tool, multimeter, wiring diagrams, backprobe kit, test light, jumper leads, and optional oscilloscope.
- Scan all modules: Identify additional ABS or voltage-related codes.
- Check pump fuse and relay: Replace if blown, loose, or overheated.
- Listen for pump self-test: Most vehicles activate the pump briefly at startup.
- Check pump ground: Remove, clean, and verify solid metal-to-metal contact.
- Test pump power supply: Confirm full battery voltage reaches the pump when commanded.
- Backprobe pump control wire: Ensure ABS module is sending activation signals.
- Check pump motor resistance: Open or shorted windings indicate failure.
- Inspect wiring harness: Look for chafing, corrosion, or trapped wires.
- Direct power test (with caution): Briefly apply 12V to pump motor to verify operation.
- Check ABS module: If pump and wiring are good, suspect internal module fault.
Pro Tip: If the pump runs during direct 12V testing but not during vehicle commands, the ABS module or pump relay is the likely culprit—not the pump itself.
Possible Fixes & Repair Costs
- Replace ABS pump motor: €200–€550+
- Repair or clean pump ground: €20–€80
- Replace pump fuse or relay: €10–€40
- Repair ABS pump wiring: €60–€200
- Replace ABS control module: €350–€900+
- Charging system repair: €120–€400
Can I Still Drive With C0110?
Yes, but it is less safe. ABS and traction control may not function, causing the wheels to lock during hard braking or on slippery roads. Stability control may also be disabled. Avoid driving in rain, snow, or high-speed conditions until repairs are completed.
Related Codes
- C0194 – Chassis Wheel Speed Signal Plausibility
- C0193 – Traction Control Torque Request Signal Range/Performance
- C0192 – Chassis Wheel Speed Signal Plausibility
- C0191 – Traction Control Torque Request Signal Low
- C0190 – Traction Control Torque Request Signal
- C0189 – Brake Wheel Speed Signal Plausibility
- C0188 – Stop Lamp Switch Circuit Range/Performance
- C0187 – Brake Wheel Speed Signal Plausibility
- C0186 – Chassis Wheel Speed Sensor Circuit Fault
- C0185 – Chassis Wheel Speed Signal Plausibility
Key Takeaways
- C0110 indicates an electrical failure in the ABS pump motor circuit.
- Common causes include a bad pump motor, corroded grounds, blown fuses, or wiring faults.
- ABS and ESC are typically disabled when this code appears.
- Testing pump power, ground, and control signals quickly identifies the root cause.
FAQ
Does C0110 always mean the pump motor is bad?
No. Wiring faults, relays, blown fuses, and poor grounds frequently trigger this code.
Can low voltage cause C0110?
Yes. A weak battery or alternator can reduce pump performance and set the code.
Is C0110 dangerous?
Potentially. ABS and traction control may not function, especially in slippery conditions.
Can I test the pump with 12V directly?
Yes, but only for a short moment and with proper caution to avoid damage.
Should I replace the ABS module?
Only after confirming the pump, wiring, fuses, and relay are functioning correctly.