Cooling

P01E5 — Engine Coolant Temperature Sensor 3 Circuit Low

Severity: medium Drive with care, to a shop

What P01E5 means

The engine control module monitors the voltage in the coolant temperature sensor 3 circuit. The sensor is a thermistor: as coolant gets hotter its resistance and signal voltage drop. P01E5 sets when the voltage falls below the expected range. The ECM reads this as extreme heat or as a short of the signal wire to ground.

Symptoms

  • Check Engine light on
  • Scan tool shows an unrealistic coolant temperature, such as very hot on a cold engine
  • Cooling fan runs constantly or at odd times
  • Poor fuel economy
  • Hard cold starts or rough running
  • Temperature gauge jumps or disagrees with real temperature

Possible causes

  1. Failed coolant temperature sensor 3 (internal short or drift)
  2. Signal wire shorted to ground from damaged insulation
  3. Corroded, wet, or damaged sensor connector
  4. Open or shorted wiring harness near the sensor
  5. ECM fault (rare)

How to diagnose

  1. Read all codes and freeze frame data, and look for other temperature sensor codes
  2. Compare sensor 3 reading with other coolant temperature readings on a cold engine
  3. Inspect the connector and harness for rubbing, corrosion, moisture, and chafed insulation
  4. Unplug the sensor: if the scan tool reading changes to an open-circuit value, the sensor is likely bad
  5. Measure sensor resistance and compare to the manufacturer's chart for the current temperature
  6. Test the signal wire for a short to ground and for continuity to the ECM
  7. Check the 5 V reference at the connector using the wiring diagram
  8. Clear the code after repair and confirm it does not return

Common fixes

  • Replace coolant temperature sensor 3
  • Repair damaged wiring and insulation
  • Clean or replace the connector
  • Diagnose and, if confirmed faulty, replace or reflash the ECM

Questions and answers

What does P01E5 mean?

It means the coolant temperature sensor 3 circuit signal is low. The ECM sees a voltage below normal, most often from a bad sensor or a short to ground.

Can I drive with P01E5?

Briefly, if the engine temperature stays normal. False readings can affect the cooling fan and fueling, so don't put off the repair.

Is replacing the sensor enough?

Not always. Check the connector and wiring first, because a short or corrosion sets the same code and a new sensor won't fix it.

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.