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DTC codes / P01xx · Fuel and air metering / P01E6

P01E6Engine Coolant Temperature Sensor 3 Circuit High

P01E6 indicates that the engine control module (ECM) has detected an abnormally high voltage on the signal circuit of engine coolant temperature (ECT) sensor 3. The ECM expects a voltage within a calibrated range that corresponds to the current coolant temperature, and a sustained high voltage typically means the signal circuit is open, shorted to voltage, or the sensor's internal resistance has increased beyond specification.

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

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Inaccurate or erratic coolant temperature gauge readings, if the vehicle is equipped with a gauge
  • Poor fuel economy or rich fuel mixture because the ECM may default to a cold-engine strategy
  • Cooling fan running continuously or not engaging at the correct temperature
  • Difficulty starting or rough idle when the engine is cold
  • Possible overheating if the ECM misjudges coolant temperature and fails to command the fan

Common causes, most likely first

  1. Open circuit in the signal wire between ECT sensor 3 and the ECM, such as a broken wire or corroded connector terminal
  2. Faulty ECT sensor 3 with an internal open circuit or excessive resistance
  3. Short to voltage on the signal circuit, often from chafed wiring contacting a power wire
  4. Poor electrical connection at the sensor or ECM connector, including loose pins or water intrusion
  5. Failed ECM driver or internal circuit for the sensor input, though this is less common
  6. Aftermarket sensor with incorrect resistance characteristics installed previously

How to diagnose and fix it

  1. Connect a scan tool and record the ECT sensor 3 voltage and temperature readings with the key on and engine cold, then compare to ambient temperature to confirm the fault is present
  2. Visually inspect the sensor and its connector for damage, corrosion, or loose terminals, and check the wiring harness for obvious chafing or breaks
  3. Measure the resistance of ECT sensor 3 with a multimeter and compare it to the manufacturer's temperature-resistance chart for the current coolant temperature
  4. Backprobe the signal circuit at the ECM connector and measure voltage with the key on; an open circuit will show a high voltage close to reference voltage
  5. Perform a voltage drop test on the ground circuit for the sensor to rule out a poor ground that can skew the reading
  6. If the wiring and connector are good but the sensor resistance is out of specification, replace ECT sensor 3 with a quality OEM-equivalent part
  7. Clear the diagnostic trouble codes and verify the repair by running the engine until the coolant reaches operating temperature and confirming the sensor reading tracks correctly

High Voltage Does Not Always Mean a Bad Sensor

  • A high voltage reading on the ECT sensor 3 circuit is more often caused by an open signal wire or a corroded connector than by a failed sensor itself, so always check the harness before replacing parts.
  • Some vehicles use multiple coolant temperature sensors for different control functions, and a fault in sensor 3 may not affect the temperature gauge or the primary sensor used for fuel control, leading drivers to ignore the warning light.
  • A short to voltage on the signal circuit can be intermittent and may only set the code when the engine harness moves or vibrates, so a wiggle test of the harness while watching live data is a valuable diagnostic step.
  • The ECM may substitute a default coolant temperature value when this code is set, which can cause the cooling fan to run constantly or fuel trim to be biased rich, and these symptoms may be mistaken for other faults.
  • Aftermarket sensors with incorrect resistance curves are a common cause of repeat codes after a repair, so using a sensor that meets the original equipment specification is critical for a lasting fix.

Can I keep driving with P01E6?

You can generally drive the vehicle short distances to a repair shop, but avoid sustained high-speed driving or heavy loads because the ECM may not control the cooling fan correctly and the engine could overheat. If the temperature gauge climbs above normal or you notice steam, stop safely and shut the engine off.

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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