OBD-II trouble code
C0161: ABS/TCS Brake Switch Circuit Malfunction
The ABS/traction control module detected an illogical or missing signal from the brake switch. The brake light switch tells the system when you're braking; a bad signal can disable ABS/traction features and sometimes affect cruise control.
Quick facts
- System
- Chassis
- Category
- ABS / Traction Control
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $20 – $200
- DIY difficulty
- Beginner DIY
What does C0161 mean?
The brake (stop lamp) switch tells several systems when the brake pedal is pressed. The anti-lock brake system (ABS) and traction control system (TCS) use that brake-applied signal to coordinate their function — for example, backing off traction control when you brake. C0161 sets when the ABS/TCS module sees a brake switch signal that is missing, contradictory, or illogical: the switch says 'braking' when other data says otherwise, or the signal is absent when it should be present. In short, the module can't trust the brake-switch input.
The most common cause is a failed or misadjusted brake light switch, since these inexpensive switches wear out and are a frequent culprit. Wiring and connector problems, a blown brake-lamp fuse, and occasionally a module fault can also trigger it. Because the ABS/TCS module relies on knowing when you brake, a fault can disable ABS and traction/stability features (warning lights on) and, on some vehicles, disable cruise control or cause brake lights that stay on or don't work. Diagnosis starts with the brake light switch and its adjustment — a quick, cheap check that resolves many C0161 cases — before moving to wiring and the module.
Common causes
- Failed or misadjusted brake light (stop lamp) switch
- Damaged or corroded wiring/connector at the brake switch
- Blown brake-lamp fuse
- Brake pedal position/switch out of adjustment after pedal or bracket work
- Poor ground affecting the switch signal
- ABS/TCS module fault (less common)
Symptoms
- ABS and/or traction-control warning lights on
- ABS and traction/stability features disabled
- Brake lights staying on, not working, or behaving erratically
- Cruise control not engaging on some vehicles
- Normal (base) braking still works
Diagnostic steps
- 1.Scan the ABS/TCS module and record all codes.
- 2.Check brake light operation — lights that stay on or don't work point straight at the switch.
- 3.Inspect and test the brake light switch and its adjustment at the pedal.
- 4.Check the brake-lamp fuse and the switch's wiring and connector for damage or corrosion.
- 5.Verify the brake-switch signal reaches the ABS/TCS module in live data when the pedal is pressed.
- 6.Replace or readjust the brake switch (or repair wiring) and clear the code; re-verify braking-signal behavior.
Repair cost
$20 – $200
A brake light switch is inexpensive — parts are often $10-$60 with quick labor, so many C0161 repairs are $30-$150. Wiring or connector repairs vary. The switch and its adjustment are the cheapest, most likely fix and should be checked first.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with brake light switch replacement preselected. Adjust labor rate and vehicle category to fit your situation.
Related repairs
DIY vs shop
This is a beginner-friendly repair. Common hand tools, a free afternoon, and a willingness to follow a procedure are usually enough. The risk of causing a bigger problem is low if you read up on your specific vehicle first.