Engine

P011F — Coolant Temp Sensor 2 / Ambient Air Temp Correlation

Severity: low Safe to drive

What P011F means

The engine control module compares the reading from the second engine coolant temperature sensor with the ambient air temperature sensor. After the engine has sat long enough to cool completely, the two values should be close. If they differ by more than expected, the ECM sets P011F and may turn on the check engine light. It points to a sensor or circuit supplying an inaccurate reading.

Symptoms

  • Check engine light on
  • Worse fuel economy
  • Rough or uneven idle
  • Temperature gauge readings that look wrong
  • Harder cold starts (sometimes)

Possible causes

  1. Faulty engine coolant temperature sensor 2
  2. Faulty ambient air temperature sensor
  3. Damaged wiring or poor connections at the sensors
  4. Corroded terminals, open circuit, or short to ground or power
  5. ECM software or calibration issue (rare)

How to diagnose

  1. Scan for all codes and review freeze frame data, looking for other temperature sensor codes
  2. With a fully cold engine, compare ECT 2 and ambient temperature readings on a scan tool
  3. Compare both with the actual temperature using a separate thermometer
  4. Inspect connectors and harness for corrosion, chafing and moisture
  5. Measure sensor resistance and compare it with the manufacturer's chart at that temperature
  6. Check the 5 V reference and ground at the sensor connector
  7. Test the wiring to the ECM for opens and shorts
  8. Check for ECM software updates or service bulletins for your vehicle

Common fixes

  • Replace the faulty coolant temperature sensor
  • Replace the ambient air temperature sensor
  • Repair the wiring and clean or replace the connectors
  • Update or reflash the ECM if the manufacturer offers a fix

Questions and answers

What does P011F mean?

The readings from coolant temperature sensor 2 and the ambient air temperature sensor don't agree within the expected range. A bad sensor or wiring problem is the most common reason.

Can I drive with P011F?

Usually yes, for short trips. Fuel economy may suffer and engine control can be less precise, so have it diagnosed soon.

How do I fix P011F?

Start with the connectors and wiring, then test the sensor resistance. Replace the bad sensor, clear the code and confirm it doesn't 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.