Cylinder head temperature sensor A faulty internally (shorted); Signal wire chafed and shorted to earth; Corroded, wet or damaged sensor connector causing low signal voltage; Signal wire shorted to another earth or sensor return wire in the harness; Faulty or low reference voltage supply from the control unit; Fault inside the engine control unit.

P017C

Cylinder Head Temperature Sensor A Circuit Low.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
1: AreaFuel and air metering
7C: FaultThe specific fault in that area

What it means

P017C is a generic code meaning the engine control unit has seen the signal voltage from cylinder head temperature sensor A fall below the expected range, which points to a short to earth or a sensor fault. The control unit sets it when the circuit reads lower than the normal operating window for a set period. Sensor location and the exact trigger thresholds vary by model and engine.

Symptoms

Engine warning light on
Engine running in a reduced-power or protective mode
Poor or rough running, especially when cold
Cooling fan running constantly or at odd times
Temperature readings that look wrong or stuck on a scan tool
Hard starting or poor fuel economy

Possible causes

Cylinder head temperature sensor A faulty internally (shorted)likely
Signal wire chafed and shorted to earthlikely
Corroded, wet or damaged sensor connector causing low signal voltagepossible
Signal wire shorted to another earth or sensor return wire in the harnesspossible
Faulty or low reference voltage supply from the control unitrare
Fault inside the engine control unitrare

How to diagnose

Read the stored codes and freeze frame data, noting engine temperature and conditions when the code set, and check for other temperature or reference voltage codes
Compare the cylinder head temperature reading on live data with coolant temperature on a cold engine; they should be close
Inspect the sensor, connector and harness for chafing, heat damage, water ingress and corrosion
Unplug the sensor with the ignition on and see whether the reading changes; check the model-specific procedure and expected values
Measure the sensor resistance against the manufacturer's temperature table
Check the signal wire for a short to earth and for continuity back to the control unit
Check the reference voltage and earth at the connector against the wiring diagram
Clear the code and road test, confirming the reading rises sensibly as the engine warms

How to fix

Replace the cylinder head temperature sensor if its resistance is out of specification
Repair or replace the damaged wiring where the signal wire is shorted to earth
Clean or replace the corroded or damaged connector and seal it against moisture
Repair any harness short between the signal circuit and earth or the sensor return
Have the control unit tested and repaired or replaced only after the wiring and sensor are proven good

Can I keep driving?

Medium severity

The car can usually be driven short distances, but the control unit may be limiting power and cannot monitor head temperature properly. Get it checked soon and watch the temperature gauge, as an undetected overheating problem could damage the engine.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.