What it means
Generic electrical fault on cylinder head temperature sensor A (CHT sensor — used on engines without conventional ECT).
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 reports engine temperature to the control module on engines that use this sensor instead of a conventional engine-coolant temperature sensor. P017A sets when the module detects a general electrical fault in sensor A’s circuit.
Common causes
Most likely first.
- Cylinder head temperature sensor A failed
- Damaged wiring or poor connector contact
- Sensor circuit fuse or shared power supply fault
Symptoms
- Check engine light on
- Temperature gauge or warning may behave abnormally
- Hard starting or rough running
- Reduced engine performance
How to diagnose it
- Read freeze-frame data and compare sensor A’s reported temperature with ambient temperature before starting and with engine warm-up behavior.
- Inspect sensor A’s connector and nearby wiring for corrosion, loose pins, heat damage, or chafing.
- Check the sensor circuit fuse and any shared power supply if other sensors or temperature readings are also affected.
- Test sensor A’s circuit power, ground, and signal continuity using the wiring information and the manufacturer's specifications.
- If the circuit is intact, test cylinder head temperature sensor A and compare its response with the manufacturer's specification.
Common fixes
- Secure a loose sensor A connector or restore clean terminal contact.
- Repair damaged wiring in the cylinder head temperature sensor A circuit.
- Replace a failed circuit fuse or repair its confirmed shared supply fault.
- Replace cylinder head temperature sensor A if it fails testing.
Can I keep driving?
Drive only if the temperature warning is normal and the engine behaves normally; stop if a temperature warning appears or the engine overheats. An unreliable temperature signal can impair starting and engine control, and missed overheating can cause serious engine damage.
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.