C0161 Code: ABS/TCS Brake Switch Circuit
The GM brake module gets a brake-light switch signal that doesn't make sense. Check your brake lights first.
Unverified: this manufacturer-specific definition comes from a single source or varies by model. Confirm it with a brand-specific scan tool.
Safety first · Consult a professional
- Braking system affected: ABS may be disabled. Drive carefully and have it checked promptly.
At a glance
Severity: Moderate
- Meaning
- ABS/TCS Brake Switch Circuit
- System
- Brakes, ABS & Chassis · Chassis
- Safe to drive?
- With caution
- Typical repair cost
- $0–$250
- DIY difficulty
- Easy
C0161 is a GM code set by the electronic brake control module when the brake (stoplamp) switch circuit misbehaves. The switch on the pedal bracket sends battery voltage to the brake lights and to the EBCM when you press the pedal; the module compares that with wheel deceleration and, on newer models, with brake pressure or pedal position. If the switch signal stays on, never appears, or flickers when it shouldn't, the module stores C0161 and disables traction control, StabiliTrak and sometimes ABS. Because the same switch also runs the brake lights, cruise control and shift interlock, this code can go along with real safety problems at the back of the car.
Can I keep driving? Check straight away that your brake lights work; if they don't, or stay on all the time, fix that before driving any distance. Otherwise braking is normal but traction and stability control are off.
Try this first – 5-minute fix
- Check the brake lights Have someone watch the lights while you press and release the pedal, or back up to a wall at night. All three should light instantly with light pedal pressure and go out fully when you let go.
- Inspect the switch and pedal pad Look under the dash at the switch above the pedal arm. Make sure its plunger touches the pedal or bumper pad and that the pad isn't cracked or missing; a dangling switch is a very common find.
- Replace or readjust the switch Brake light switches are inexpensive and usually twist or clip out. Adjust the new one exactly as the service information says, since many self-adjust when you pull the pedal up after fitting.
- Clear codes and test Clear the EBCM and engine codes, then drive and use the brakes a few times. Confirm cruise control works and the warnings stay off.
How to read C0161
- C Chassis
- 0 Generic (SAE)
- 1 Brakes, ABS & Chassis
- 61 Specific fault
Symptoms
- Brake lights stuck on, dead, or only working with a firm press
- ABS, traction control or StabiliTrak warning on
- Cruise control won't set or cancels by itself
- Shifter hard to move out of Park on some models
- Push-button start doesn't respond to the brake pedal
- Engine code P0571 stored alongside
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Worn, sticky or misadjusted brake light switch on the pedal bracket
- Burned-out brake lamp bulbs or failed third brake light changing the circuit load
- Missing or broken pedal bumper pad letting the switch plunger sit wrong
- Trailer wiring or LED conversion feeding voltage back into the stoplamp circuit
- Damaged wiring or loose connector at the switch or EBCM
- Blown stoplamp fuse
Diagnosis step by step
Watch the switch input live
In the EBCM data, the brake switch status should change from Released to Applied the instant the pedal moves, before any real pressure builds. A delay, flicker or permanently applied status confirms the switch or circuit.
Tools: OBD-II scanner
Check the fuse and supply
Test for battery voltage on the switch supply terminal with the key off and on, depending on the vehicle. No voltage there points to the stoplamp fuse or its feed.
Tools: Multimeter
Test the switch output
With the pedal released, the output should be close to 0 V; pressed, within about 0.5 V of battery voltage. A switch that shows a few volts at rest or needs a hard press to switch is worn or misadjusted.
Tools: Multimeter
Look for backfeed
If aftermarket trailer wiring, LED bulbs or an extra brake light are fitted, unplug them and retest. Voltage appearing on the stoplamp circuit with the pedal released means something is feeding it.
Tools: Multimeter, Flashlight
Check wiring to the module
Measure from the switch output to the EBCM input pin while flexing the harness at the pedal bracket. Look for chafing where the harness passes the pedal hinge.
Tools: Multimeter
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Readjust switch or replace pedal bumper pad | Yes | $0–$60 |
| Replace brake light switch | Yes | $25–$180 |
| Replace brake bulbs or third brake light | Yes | $10–$200 |
| Repair trailer wiring backfeed or stoplamp circuit | No | $80–$250 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Field data
| Chevrolet | 3 | Malibu Maxx, Silverado 1500, Traverse |
|---|
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Depends
C0161 doesn't affect an OBD emissions test. Non-working brake lights fail any state safety inspection, and a lit ABS or stability warning can too.
Frequently asked questions
Why does a brake light switch disable traction control?
Traction and stability control must never fight the driver's braking. If the module can't trust the switch, it can't be sure when you're braking, so it switches those systems off to be safe.
Can burned-out bulbs cause C0161?
On some GM models, yes. The bulbs form part of the circuit load, so with them out the switch signal line can float to a voltage the module reads as partly applied.
The engine computer also stored P0571. Is that a second problem?
Usually not. The engine computer reads the same switch for cruise control, so P0571 and C0161 together almost always point to one faulty switch or circuit.
Is C0161 the same as C0040 on Ford or Jeep?
It's a similar fault. The newer SAE list calls C0040 'Brake Pedal Switch A', which some non-GM vehicles use, while GM uses C0161 for its brake switch circuit.
Sources
- Manufacturer public service information (cross-checked)
- NHTSA Complaints API
- Methodology: How We Build Code Pages · Data Sources We Use · Editorial Policy