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DTC codes / P01xx · Fuel and air metering / P017D

P017DCylinder Head Temperature Sensor A Circuit High

P017D means the powertrain control module (PCM) has detected an abnormally high voltage signal from the cylinder head temperature (CHT) sensor A circuit, which typically indicates an open circuit, a short to voltage, or a sensor that has failed high. The PCM uses this sensor to infer cylinder head metal temperature for fuel and spark control, so a high reading can make the engine run poorly or trigger the warning light.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough idle or stumbling when the engine is cold
  • Poor fuel economy or rich-running smell from the exhaust
  • Hard starting or extended cranking, especially in cold weather
  • Overheating gauge or warning if the PCM substitutes a default temperature
  • Intermittent driveability issues that appear when the engine bay is hot or wet

Common causes, most likely first

  1. Open circuit in the CHT sensor signal wire or ground circuit
  2. Short to voltage on the signal wire, often from chafed insulation near hot components
  3. Failed CHT sensor with an internal open or high-resistance element
  4. Corroded, loose, or water-intruded connector pins at the sensor or PCM
  5. Damaged wiring harness from heat, vibration, or previous engine work
  6. PCM internal fault on the sensor input circuit (rare but possible)

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data to confirm P017D is the primary fault and not a companion code
  2. Inspect the CHT sensor connector and wiring for corrosion, looseness, or obvious damage, then clean and reseat
  3. Measure sensor resistance with a multimeter and compare to the manufacturer's temperature-resistance chart
  4. Backprobe the signal circuit at the PCM and check voltage with the key on, engine off, looking for a high or open reading
  5. Perform a voltage drop test on the sensor ground circuit to rule out high resistance
  6. Repair or replace the faulty section of harness, then clear codes and verify the CHT reading agrees with actual engine temperature
  7. If wiring and sensor test good, follow the factory diagnostic flow for PCM pin and internal circuit checks before condemning the PCM

What a high CHT reading really means

  • A high voltage on the CHT circuit usually means the PCM is seeing an open circuit or a short to voltage, not necessarily a failed sensor, so wire inspection comes before parts replacement.
  • Many vehicles use the CHT sensor in place of a conventional coolant temperature sensor, so a P017D can cause cooling fan and temperature gauge faults that owners misattribute to the thermostat.
  • The sensor element is often a thermistor whose resistance drops as temperature rises, so an open element reads high voltage and a shorted element reads low voltage, which is why P017D and P017C are opposites.
  • Heat soak after shutdown can temporarily push a marginal CHT circuit out of range, so intermittent codes may only appear after a hot restart and not during a cold-start test.
  • A poor ground at the engine block can elevate the CHT signal voltage and set P017D even when the sensor and signal wire test perfectly.

Can I keep driving with P017D?

You can usually drive a short distance to a repair shop if the engine runs normally and the temperature gauge behaves, but avoid heavy loads, towing, and long trips because a false high CHT reading can cause rich fueling, poor cold running, or cooling fan errors. Stop driving if the engine overheats or runs very poorly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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