What it means
CHT sensor A signal voltage below expected range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Cylinder head temperature sensor A sends a signal to the control module on engines that use this sensor instead of a conventional coolant-temperature sensor. P017C sets when the signal falls below the circuit’s expected range, often because the signal wire is grounded or the connector has poor contact.
Common causes
Most likely first.
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on
- Temperature gauge or warning may behave abnormally
- Hard starting or rough running
- Reduced engine performance
How to diagnose it
- Use freeze-frame and live data to confirm sensor A is reading unusually low or has dropped out.
- Inspect sensor A’s connector for moisture, corrosion, pushed-back pins, and the signal harness for chafing against ground.
- With the code active, gently move the harness while watching the sensor reading to help find an intermittent short or contact fault.
- Test sensor A’s signal wire for a short to ground and check connector contact and circuit continuity against the manufacturer's specifications.
- If the wiring passes, test cylinder head temperature sensor A and replace it only if its output remains below range.
Common fixes
- Repair chafed insulation where sensor A’s signal wire is shorted to ground.
- Restore corroded or pushed-back connector terminals and seal out moisture.
- Repair damaged harness wiring or poor circuit continuity.
- Replace cylinder head temperature sensor A if it fails testing.
Can I keep driving?
Drive cautiously only if the temperature warning and engine behavior remain normal; stop if an overheating warning appears or the engine runs abnormally. A low signal can mislead temperature-based control and may prevent the module from recognizing an overheating condition.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.