ABS Power Relay Output Open Circuit
The C1186 code indicates that the ABS control module has detected an open circuit in the output of the ABS power relay. This relay supplies battery voltage to the solenoid valves and pump of the hydraulic modulator. An open circuit prevents the ABS system from activating, disabling the anti-lock braking function and turning on the ABS warning light on the dashboard.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty ABS power relay with open internal contacts
- Blown fuse in the ABS relay power circuit (commonly a 40A or 60A fuse in the engine fuse box)
- Damaged, corroded, or disconnected wiring between the relay, fuse, and ABS module (HU/ECU)
- Poor ground connection for the relay or ABS module
- Internal failure of the hydraulic control unit (HCU) or electronic brake control module (EBCM)
3. Symptoms You Will Notice
- ABS warning light illuminated on the dashboard
- ABS system inoperative (wheels may lock during hard braking)
- Possible loss of traction control or stability assist functions
4. Step-by-Step Diagnosis
Check the ABS power relay fuse (typically 40A or 60A) in the engine fuse box; replace if blown.
Test the ABS power relay for proper operation: apply battery voltage to the coil and check for continuity across the switch contacts.
Inspect wiring and connectors between the relay, fuse, and ABS module for damage, corrosion, or loose connections.
Verify the ground circuit for the relay and ABS module is clean and tight.
If all external circuits check out, the ABS module (HCU/EBCM) may be faulty and require professional diagnosis or replacement.
5. Frequently Asked Questions
Is it safe to drive?▼
Driving is possible but not recommended, especially in slippery conditions. The ABS system will not function, increasing the risk of wheel lockup and loss of control during hard braking. Have the issue diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs vary widely. A simple relay or fuse replacement can cost $20–$100. Wiring repairs range from $100–$300. If the ABS module needs replacement, expect $500–$1,500 including parts and labor.