What it means
The ABS or traction control module has detected a fault in the brake switch circuit. It sets the code when the brake switch signal fails the vehicle’s circuit or plausibility checks; the precise conditions vary by vehicle.
How it works
The ABS or traction-control module monitors the brake switch circuit to determine when the driver presses the brake pedal. C0161 sets when the switch signal is electrically faulty or does not pass the vehicle’s plausibility checks, which can interfere with brake lights, cruise control, or stability functions.
Common causes
Most likely first.
- Faulty or misadjusted brake switch
- Damaged wiring or connector
- Blown brake light fuse
- Poor connection or ground
- Fault in the ABS or traction control module
Symptoms
- ABS or traction control warning light
- Traction or stability control may be unavailable
- Brake lights may not work correctly
- Cruise control may not operate
How to diagnose it
- Check whether the brake lights illuminate consistently when the pedal is pressed, and note any cruise-control or ABS/traction warnings.
- Read freeze-frame data and related codes, then compare the brake-switch status in live data with the pedal released and pressed.
- Inspect the brake switch, its adjustment, connector, and wiring for looseness, damage, or corrosion.
- Check the brake-light fuse and the switch’s power, ground, and output circuits using the vehicle wiring diagram and manufacturer’s specification.
- If the switch and wiring pass their checks, follow the vehicle-specific procedure to test the ABS or traction-control module input.
Common fixes
- Replace a blown brake-light fuse after checking for the cause of the fuse failure.
- Adjust or reconnect the brake switch if it is mispositioned or loose.
- Repair damaged wiring, connectors, or grounds in the brake switch circuit.
- Replace the brake switch if its signal fails the specified test.
- Repair or replace the ABS or traction-control module only if its input circuit is confirmed faulty.
Can I keep driving?
Check the brake lights before driving; if they do not work reliably, do not drive in traffic because following drivers may not see you slowing. Even with working brake lights, ABS or stability assistance and cruise control may be unavailable, so drive cautiously and get the fault checked promptly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.