P017BCylinder Head Temperature Sensor A Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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. P017B means the signal is electrically valid but implausible – for example it does not fit other temperature sensors after a long standstill or does not rise as expected. Audi documents it on 2019–2021 V8 TFSI models and Bentley on V8 models from 2018 onwards, together with a cooling system fault code and a red coolant warning: a damaged O-ring at the sensor tip lets water into the housing and damages the sensing element, often intermittently; the fix is a new sender. GM lists P017B only as an exclusion condition in its diesel software. Thresholds are not public.
- What you may notice
- Check engine light on
- Red coolant warning or overheating warning
- Radiator fan runs loud or constantly
- Possibly reduced power
- Likely causes
- LikelySensor damaged by moisture (O-ring)
- PossibleGenuine temperature problem (air in cooling system, thermostat)
- PossibleContact resistance at the connector
- RareSoftware or calibration
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.