P011F
Engine Coolant Temperature 2 / Ambient Air Temperature Correlation.
- Generic
- Powertrain
- Generic code
- Low severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 1
- AreaFuel and air metering
- 1F
- FaultThe specific fault in that area
What it means
P011F means the control unit compared the reading from the second engine coolant temperature sensor (ECT 2) with the ambient air temperature reading and found they did not agree as expected. The check is normally made after the engine has been switched off long enough for everything to cool to a similar temperature. A mismatch points to a sensor, wiring or data fault in either the ECT 2 or the ambient temperature circuit, or to a genuine cooling system problem.
Symptoms
- Engine warning light on
- Incorrect or erratic coolant temperature gauge reading
- Cooling fans running unexpectedly or at the wrong time
- Hard or rough starting, especially when cold
- Poor fuel economy or rough running while warming up
- No noticeable symptoms other than the stored code
Possible causes
- Faulty or drifting ECT 2 sensor reading out of rangelikely
- Faulty ambient air temperature sensor or its signal giving a wrong valuelikely
- Damaged wiring, corroded terminals or poor connector contact in the ECT 2 or ambient sensor circuitlikely
- Engine not fully cooled when the test ran, for example a short soak or heat soak in the engine bay, affecting the comparisonpossible
- Cooling system fault such as low coolant, air in the system or a stuck thermostat or valve affecting the ECT 2 locationpossible
- Fault in the data source for ambient temperature on vehicles that receive it over the network from another modulepossible
- Control unit internal fault or outdated softwarerare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting coolant temperatures and ambient temperature at the time the code set.
- Check for other temperature sensor codes, as these help to show which sensor is at fault.
- With the engine fully cold after a long soak, compare live ECT 2, ECT 1 (if fitted), intake air and ambient temperature readings; they should all be close.
- Inspect the ECT 2 and ambient sensor wiring and connectors for damage, water ingress, corrosion and loose pins.
- Check coolant level and condition, and look for leaks or signs of air in the system.
- Measure the ECT 2 sensor resistance or signal voltage against the manufacturer's temperature table, and check the sensor reference and ground circuits.
- Verify the ambient temperature value against a known accurate thermometer and check how this vehicle gets that signal (own sensor or network data).
- Check for applicable software updates or technical bulletins for the model and engine, as the sensor location and strategy vary.
How to fix
- Replace the ECT 2 sensor if its readings are inaccurate or out of specification.
- Replace the ambient air temperature sensor if it reads incorrectly.
- Repair or replace damaged wiring and clean or renew corroded connectors.
- Top up and bleed the cooling system, and repair any leaks or faulty thermostat or valve found.
- Repair the source of the ambient temperature data if it comes from another module.
- Apply a manufacturer software update only if an outdated calibration is confirmed as the cause.
Can I keep driving?
The car can normally be driven and booked in for diagnosis. If the temperature gauge reads abnormally high or coolant is being lost, stop and have the cooling system checked before driving further.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.