Cooling

P01E7 — Engine Coolant Temperature Sensor 3 Circuit Intermittent

Severity: medium Drive with care, to a shop

What P01E7 means

The engine control module detected that the signal from the third engine coolant temperature (ECT 3) sensor drops out or jumps in a way that doesn't match real engine warm-up. The sensor is normally a thermistor, and the module reads its temperature from the voltage across it. That data helps control the cooling fan, fuel mixture and other functions. Which sensor is number 3 and where it sits depends on the engine.

Symptoms

  • Check Engine light comes on and off
  • Erratic coolant temperature readings
  • Cooling fan runs at the wrong time or constantly
  • Rough running or hard starting
  • Worse fuel economy

Possible causes

  1. Failing ECT 3 sensor
  2. Poor contact or corrosion in the sensor connector
  3. Damaged, chafed or broken wiring harness
  4. Wire shorted to ground or power, or an open circuit
  5. Rarely, a fault in the control module input
  6. Low coolant or an air pocket around the sensor

How to diagnose

  1. Scan for codes and freeze frame data and look for other temperature-related codes
  2. Check the coolant level and bleed any air from the system
  3. Compare ECT 3 readings with other temperature sensors and actual temperature on a scan tool
  4. Inspect the sensor connector and harness for corrosion, oil and chafing
  5. Wiggle the harness and connector with the engine running while watching live data
  6. Measure sensor resistance cold and warm and compare with specs
  7. Check the 5 V reference and ground at the connector
  8. If wiring and sensor are good, test the control module

Common fixes

  • Replace the ECT 3 sensor
  • Clean or replace the connector and terminals
  • Repair or replace damaged wiring
  • Top off and bleed the cooling system
  • As a last resort, diagnose, reprogram or replace the control module

Questions and answers

What does P01E7 mean?

The engine computer sees an unstable, on-and-off signal from the third coolant temperature sensor. The sensor, its connector or the wiring is the usual culprit.

Can I drive with P01E7?

Briefly, if the gauge reads normal. Don't put off the repair, because bad data can make the fan run incorrectly and the engine could overheat.

How do I fix P01E7?

Check the coolant level, connector and wiring first. If those are fine, replace the sensor, clear the code and see if it returns.

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.