C1185

Symptoms

• ABS warning light on (often intermittent — on Ford trucks the light can be sensitive to bumps, a classic sign of a cracked solder joint)
• ABS inoperative
• on affected GM trucks
• ABS and StabiliTrak lights with 'Service StabiliTrak' messages.

Probable causes

• 1) Ford trucks 1997-2004 (F-150, Expedition and similar): almost always cracked solder joints on the ABS module's internal circuit board — extremely common failure. 2) Damaged or corroded wiring/connectors causing high resistance or loss of connection between the power source and the ABS module. 3) Corroded chassis ground connection causing a voltage drop the module reads as power failure. 4) Failed plug-in ABS relay in the fuse box (burned coil or pitted contacts). 5) GM trucks 2017-2019: TSB 18-NA-144 documents the chassis harness chafing against the frame
• shorting the ABS power circuit and mimicking module failure
• 2007-2014 Silverado/Sierra/Tahoe are also known for EBCM failure.

Diagnostic steps

1. Read ABS codes with a scan tool and confirm C1185 is current.
2. Check the ABS fuses and the ABS power relay if the vehicle uses a plug-in relay in the fuse box.
3. Inspect wiring and connectors between the battery/fuse box and the ABS module for damage, corrosion or chafing — on 2017-2019 GM trucks specifically check the main chassis harness against the frame per TSB 18-NA-144.
4. Check and clean the chassis ground connections for the ABS module; a corroded ground causes a voltage drop the module interprets as power failure.
5. On 1997-2004 Ford trucks, suspect the ABS module itself: the internal solder joints crack (intermittent light over bumps is the classic symptom) — repair or replace the module.
6. Clear codes and verify the ABS light stays off during a road test, including over rough surfaces.