C1278: OBD-II code C1278 is informational — the PCM has temporarily inhibited traction control (usually to protect the engine or transmission), not a hardware fault.

Symptoms

• The traction control warning lamp may illuminate briefly, then extinguish when the inhibiting condition clears.
• Traction control interventions are suspended while the PCM is protecting the engine (overheat, misfire, transmission slip, etc.).
• Standard braking and ABS remain fully functional; only traction control is temporarily suppressed.

Common causes

• An active engine coolant overheat or high transmission fluid temperature condition that suspends TCS to protect the drivetrain.
• A running misfire or fuel trim fault causing the PCM to inhibit torque changes from TCS until the root cause is fixed.
• An accompanying powertrain DTC (misfire, coolant, transmission slip) is the actual underlying problem, not C1278 itself.

What to do?

Read all PCM and TCM codes first — C1278 is a companion, not the root cause. Fix any active powertrain fault (misfire, cooling, transmission), then clear codes and retest. If C1278 sets without any powertrain code, verify serial data bus communication between the PCM and the EBCM.