C0242: Engine computer reporting a fault that blocks traction control
PCM indicated traction control system malfunction
Severity: Inspect soon
Saab service information (GM-based) says this code means traction and stability control are switched off for the ignition cycle, so that safety net is missing until the fault behind it is fixed.
C0242 in short
C0242 means the engine computer told the brake control module it has a fault and cannot allow traction control to work, so traction and stability control switch off. The cause is usually another engine code. Normal driving is possible, but without that safety net, so have it checked soon.
The brake control module runs traction control by asking the engine computer to cut engine torque when a wheel slips. If the engine computer reports a fault that stops it from doing that, the brake module stores C0242 and turns traction control off.
Saab service information, on a GM-based car, says the code sets when the engine computer sends a message that torque reduction is not allowed, and that traction and stability control stay off for that ignition cycle with the indicator lit. A code reference lists the same meaning for Holden, another GM brand.
The code is a symptom of something else. Both sources point to the engine computer's own codes first.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: A fault stored in the engine computer
Common general cause- Why it ranks here
- The brake module sets C0242 only because the engine computer says it cannot support traction control, so an engine-side fault is the usual reason.
- What would change this
- Rises if other engine codes are stored. Falls if the engine computer has no codes at all.
Cause 2: Engine control module fault
Possible — needs testing- Why it ranks here
- Saab's procedure replaces the engine module only when its own code (P0856) is the only one stored, so this is a last step on that car and not a first suspect on others.
- What would change this
- Rises if the engine computer is the only module with a code and wiring checks pass. Falls if other engine codes explain it.
Cause 3: Electronic brake control module
Possible — needs testing- Why it ranks here
- Saab says to replace the brake module only if the code returns after the engine module work, so it ranks last.
- What would change this
- Rises if C0242 returns after the engine side is cleared. Falls if the engine computer still reports a fault.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read the codes in the engine computer and the brake control module, and note every code stored with C0242.
IfThe engine computer has other stored codes
It meansFix those first; C0242 follows from them.
IfOnly C0242 is stored and the engine computer has no codes
It meansHave a shop check the engine and brake module data link and the modules themselves.
Step 2: Have a shop clear the codes and see which module resets first, then test power, ground and communication to the engine and brake modules.
Warning:This is a brake-system component. Module replacement and programming should be done by a shop.
IfThe engine computer sets a code again
It meansThe engine side is the source.
IfOnly C0242 returns after the engine side is clear
It meansThe brake control module is suspect.
Symptoms
- Traction control or stability control warning light on
- Traction control no longer intervenes when the road is slippery
- Check engine light on at the same time, if the engine computer has a fault
- Brake or ABS warning light on together with the stability control light Gets more serious: stop and have it checked.
How to fix
This is a safety-critical system, so we explain the code but don't give repair steps. Have it inspected by a qualified technician.
Parts and cost context
- Engine control module (ECM / PCM):Replacement is a last step and needs programming. Labor varies; get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
We don't have reviewed vehicle-specific evidence for C0242 yet. The causes and tests above apply across vehicles.
Related codes
No curated relationships for C0242 yet.
C0242 questions
Do I need to replace the ABS module for C0242?
Not first. Both sources say the cause is on the engine side, and Saab replaces the brake module only if the code returns after the engine work.
Will the brakes still work?
The sources say traction and stability control are switched off. They do not describe loss of normal braking, but a red brake warning light means stop and have it checked.
Sources and review
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error