Engine

P017C — Cylinder Head Temperature Sensor Circuit Low

Severity: medium Drive with care, to a shop

What P017C means

The engine control module detected that the signal voltage from the cylinder head temperature sensor is below the expected range. The sensor is normally a thermistor whose resistance changes with temperature, letting the ECM calculate how hot the cylinder head is. A voltage that is too low usually points to a signal wire shorted to ground or a failed sensor. The ECM uses this data to protect the engine from overheating.

Symptoms

  • Check Engine light on
  • Cylinder head temperature reading missing or clearly wrong
  • Reduced engine power (limp mode) in some cases
  • Cooling fan running incorrectly
  • Possible increase in fuel consumption

Possible causes

  1. Failed cylinder head temperature sensor (internal short)
  2. Signal wire shorted to ground from damaged insulation
  3. Moisture or oil in the connector, corroded terminals
  4. Wiring harness chafed against engine parts
  5. ECM fault (uncommon)

How to diagnose

  1. Scan for codes and freeze frame data, and look for other temperature-related codes
  2. On a cold engine, compare the cylinder head temperature reading with coolant temperature
  3. Inspect the sensor connector and harness for chafing, melting, moisture or corrosion
  4. Unplug the sensor: if the code changes to a high/open circuit, the sensor is the likely culprit
  5. Measure the sensor resistance and compare with the spec for your vehicle
  6. Check the signal wire for a short to ground with the sensor and ECM connectors disconnected
  7. Verify the 5 V reference at the sensor connector
  8. If wiring and sensor are good, test the ECM

Common fixes

  • Replace the cylinder head temperature sensor
  • Repair or replace the damaged wiring section
  • Clean or replace the connector
  • Diagnose, repair or reprogram the ECM if a fault is confirmed

Questions and answers

What does P017C mean?

The ECM found a low voltage signal in the cylinder head temperature sensor circuit. The most common causes are a bad sensor or a signal wire shorted to ground.

Can I drive with P017C?

For a short time, yes, but overheating protection may not work. Monitor coolant temperature and get it repaired soon.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.