What it means
CHT sensor A signal voltage above 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 temperature signal to the control module on engines that use a cylinder-head sensor rather than a conventional coolant-temperature sensor. P017D sets when that signal rises above the expected circuit range, which can happen with an open signal path, poor contact, or a wire shorted to voltage.
Common causes
Most likely first.
- Signal wire open
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Temperature gauge or warning may behave abnormally
- Hard starting or rough running
- Reduced engine performance
How to diagnose it
- Check freeze-frame and live data to confirm sensor A is reading unusually high or has dropped out at a high value.
- Inspect sensor A’s connector and harness for loose pins, corrosion, broken wires, or wiring pinched against a power source.
- Check continuity through the signal and ground paths, and test the signal wire for a short to voltage using the manufacturer's specifications.
- Move the harness gently while watching live data to help locate an intermittent open or short.
- If the circuit checks pass, test cylinder head temperature sensor A and verify its output against the manufacturer's specification.
Common fixes
- Repair an open or broken wire in the sensor A circuit.
- Restore corroded or loose connector contacts.
- Repair a signal wire pinched against a voltage source or damaged harness insulation.
- Replace cylinder head temperature sensor A if it fails output testing.
Can I keep driving?
Avoid driving if the temperature warning is abnormal or the engine runs poorly; stop if overheating is suspected. A high or invalid reading can disrupt temperature-based engine control, while an inaccurate temperature indication can make overheating harder to assess.
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.