What it means
The module detects that engine coolant temperature and intake air temperature readings do not correlate within the expected limits.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The engine coolant temperature sensor measures engine temperature, while the intake air temperature sensor measures incoming air; the control module compares both readings for plausibility. P011B sets when coolant and intake temperatures do not correlate as expected for the vehicle's operating conditions.
Common causes
Most likely first.
- Coolant or intake air temperature sensor drifting or biased
- Faulty sensor wiring or connector
- Poor electrical connection or corrosion
- Less commonly, a module fault
Symptoms
- Check engine light on
- Cooling fan runs constantly or not at all
- Cabin heater weak or excessively hot
- Possible long warm-up time or hard cold start
How to diagnose it
- Before a cold start, compare ECT and IAT live data with ambient temperature; large unexplained differences can identify a biased reading.
- Review freeze-frame data and watch both temperature readings during warm-up to see which one responds implausibly.
- Inspect the ECT and IAT sensor connectors and wiring for corrosion, loose contacts, or heat and chafing damage.
- Check coolant level and look for conditions such as an engine that warms unusually slowly, which can affect the ECT comparison.
- Test the sensor outputs and circuits that disagree against the manufacturer's specifications before suspecting the control module.
Common fixes
- Reconnect a loose ECT or IAT connector and secure its harness.
- Repair corroded connectors or damaged wiring in the sensor circuit that is producing the implausible reading.
- Correct low coolant or repair a thermostat fault if it prevents normal engine warm-up.
- Replace the ECT or IAT sensor shown by testing to be biased or out of specification.
Can I keep driving?
If the engine temperature stays normal and it runs smoothly, a short drive is generally possible; stop if it overheats. The mismatch can affect cold-start fueling and emissions, and a cooling-system fault behind it could worsen.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.