P017B Cylinder Head Temperature Sensor A Range/Performance

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.

Likely causes

Symptoms

• Check engine light on
• Red coolant warning or overheating warning
• Radiator fan runs loud or constantly
• Possibly reduced power

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.