OBD-II trouble code
C0242: PCM Indicated Traction Control Malfunction
The engine computer told the brake/stability module it cannot perform a requested torque reduction for traction control, usually because of a separate engine fault. Traction and stability control are disabled until the underlying problem is fixed.
Quick facts
- System
- Chassis
- Category
- ABS / Traction Control
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $75 – $700
- DIY difficulty
- Intermediate DIY
What does C0242 mean?
C0242 is a chassis code that sets when the Powertrain Control Module (PCM/ECM) sends a serial data message to the Electronic Brake Control Module (EBCM) indicating it cannot carry out a torque-reduction request for traction control. Traction control works by the brake module asking the engine module to briefly cut engine torque when a driven wheel spins. If the engine computer detects a fault in its own throttle or torque-management system, it reports that it cannot perform that reduction, and the brake module logs C0242 and disables traction and stability control.
Like its sibling C0240, this code is a messenger, not the root cause. It is the brake system reporting that the engine system has a problem — the real fault lives in the powertrain and will be reflected in accompanying powertrain (P) codes. The single most common cause on GM vehicles is a throttle or accelerator pedal position sensor voltage correlation fault, where the two throttle or pedal signals disagree and the PCM deems throttle control unreliable. Codes such as P2135 (throttle position correlation), P2138 (pedal position correlation), and P0641 (sensor reference voltage) resolve the large majority of C0242 cases when repaired.
Because the fault disables torque management, the vehicle often also enters a reduced-engine-power state as a protective measure. That is why a C0242 frequently arrives together with a 'Reduced Engine Power' or 'Service Traction Control' message.
C-code definitions vary by manufacturer, so confirm your specific make and model's meaning. The universal takeaway is the same: never condemn the EBCM or ABS module for C0242. Read all codes, fix the underlying powertrain fault, and this code clears with it.
Common causes
- Throttle position sensor voltage correlation fault (P2135) — the number-one cause on GM vehicles
- Accelerator pedal position sensor voltage correlation fault (P2138)
- Sensor reference voltage circuit fault (P0641) affecting multiple sensors
- Electronic throttle body or throttle actuator control failure
- Reduced-power / limp condition from another powertrain fault
- Internal PCM/ECM fault or a serial data problem between the PCM and EBCM
Symptoms
- Traction control and stability control (StabiliTrak/ESC) disabled with warning lights on
- Service Traction Control / Service StabiliTrak message
- Reduced Engine Power message and sluggish acceleration
- Check engine light with accompanying powertrain codes
- Loss of automatic wheel-slip control on slippery surfaces
Diagnostic steps
- 1.Scan all modules and record every code. The accompanying powertrain (P) codes — not C0242 itself — identify the real fault.
- 2.Prioritize any throttle/pedal correlation codes (P2135, P2138) or reference-voltage code (P0641); repairing these resolves over 90% of C0242 cases.
- 3.If a Reduced Engine Power message is present, follow the manufacturer's electronic throttle body and pedal-assembly test procedure.
- 4.Inspect throttle and pedal connectors and the 5-volt reference circuits for corrosion, chafing, and shorts.
- 5.Confirm the PCM has proper power, grounds, and voltage before suspecting the module itself.
- 6.Do NOT replace the EBCM/ABS module — fix the engine-side cause, clear codes, and verify traction control re-enables.
Repair cost
$75 – $700
Cost is driven by the underlying powertrain fault. Diagnosis is typically $75-$150. A throttle/pedal sensor or reference-voltage repair runs $150-$400, and an electronic throttle body replacement — a very common GM fix — commonly runs $250-$700 in parts and labor. C0242 needs no separate repair once the root cause is corrected.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with check engine light diagnosis preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.