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.
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
- Red coolant warning or overheating warning
- Radiator fan runs loud or constantly
- Possibly reduced power
Most likely causes
- Sensor damaged by moisture (O-ring)
- Genuine temperature problem (air in cooling system, thermostat)
- Contact resistance at the connector
- Software or calibration
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 P017B means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- 7B: Specific fault in that system
Frequently asked questions
Can I keep driving with code P017B?
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 P017B?
The most common causes are: sensor damaged by moisture (O-ring); genuine temperature problem (air in cooling system, thermostat); contact resistance at the connector.
Related codes
- P017ACylinder Head Temperature Sensor A Circuit
- P017CCylinder Head Temperature Sensor A Circuit Low
- P017DCylinder Head Temperature Sensor A Circuit High
- P017ECylinder Head Temperature Sensor A Circuit Intermittent/Erratic
- P0116Engine Coolant Temperature Sensor 1 Circuit Range/Performance
- P2181Cooling System Performance
Sources
- law.cornell.edu: 13 CCR 1968.2
- static.nhtsa.gov: MC 10193039 0001
- static.nhtsa.gov: MC 10242911 0001
- static.nhtsa.gov: MC 11008400 0001
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.