The cylinder head temperature sensor A is an NTC thermistor that measures the temperature of the cylinder head metal or of the coolant in the head. Some Ford engines use it instead of a coolant temperature sensor and calculate a coolant value from it; VW group V8 petrol engines use it as sender G407. CARB requires such sensors to be monitored like the coolant sensor. P017C means the signal voltage is too low – a short to ground of the signal wire or a short inside the sensor; the control module would read an implausibly hot cylinder head. 'Low' refers to the signal, not the temperature. Audi and Bentley document it as a short to ground, most often caused by water inside sender G407 after O-ring damage. Ford flags the same condition on its own code below 0.244 V for 5 s. A substitute value is used; an overheating warning with a cold engine is a typical sign.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Symptoms
- Check engine light on
- Overheating or coolant warning despite a cold engine
- Radiator fan runs constantly
Most likely causes
- Water or coolant inside the sensor (O-ring damaged)
- Signal wire chafed against ground
- Sensor shorted internally
- Engine control module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P017C means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- 7C: Specific fault in that system
Frequently asked questions
Can I keep driving with code P017C?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P017C?
The most common causes are: water or coolant inside the sensor (O-ring damaged); signal wire chafed against ground; sensor shorted internally.
Related codes
- P017ACylinder Head Temperature Sensor A Circuit
- P017BCylinder Head Temperature Sensor A Range/Performance
- P017DCylinder Head Temperature Sensor A Circuit High
- P017ECylinder Head Temperature Sensor A Circuit Intermittent/Erratic
- P0117Engine Coolant Temperature Sensor 1 Circuit Low
Sources
- law.cornell.edu: 13 CCR 1968.2
- static.nhtsa.gov: MC 10193039 0001
- static.nhtsa.gov: MC 11008400 0001
- newtonnet.co.uk: fordobd2012
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.