Engine

P017B — Cylinder Head Temperature Sensor Signal Out of Range

Severity: medium Drive with care, to a shop

What P017B means

P017B is an ISO/SAE reserved code, so its definition can differ between manufacturers. Scan tools most often read it as the cylinder head temperature sensor signal being out of range or behaving implausibly. This sensor tells the engine computer how hot the head really is, and the computer uses it to protect the engine and adjust operation. When the reading doesn't match expected values or other temperature sensors, the code is set.

Symptoms

  • Check Engine light on
  • Erratic or incorrect engine temperature readings
  • Rough idle or reduced performance
  • Cooling fan running constantly on some vehicles
  • No noticeable symptoms on some vehicles

Possible causes

  1. Failed or drifting cylinder head temperature sensor
  2. Damaged wiring, corroded terminals or a poor connector at the sensor
  3. Open circuit, or short to ground or voltage in the signal wire
  4. A real cooling problem such as low coolant, trapped air or a stuck thermostat
  5. PCM fault (uncommon)

How to diagnose

  1. Scan all codes and review freeze-frame data, looking for other cooling or temperature sensor codes
  2. Check coolant level and condition, and look for leaks or air pockets
  3. Compare the head temperature and coolant temperature readings on a cold engine; they should be close
  4. Inspect the harness and connector for chafing, moisture, corrosion and a loose fit
  5. Measure sensor resistance and compare it with the manufacturer's chart at a known temperature
  6. Check reference voltage, signal wire and ground with a multimeter
  7. Test the thermostat and cooling fan operation
  8. If wiring and sensor are good, check for PCM software updates from the manufacturer

Common fixes

  • Replace the cylinder head temperature sensor
  • Repair the wiring or replace the damaged connector
  • Fix any cooling system fault and bleed the system
  • Update PCM software, or replace the module as a last resort

Questions and answers

What does P017B mean?

It is a reserved code most often linked to an implausible cylinder head temperature sensor signal. The exact meaning depends on the manufacturer, so check the documentation for your vehicle.

Can I drive with P017B?

Only briefly and carefully, while watching engine temperature. Don't put off diagnosis, because real overheating could go unnoticed.

How do I clear P017B?

Find and fix the cause first, then clear the code with a scan tool. If the fault remains, the code will return.

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.