Engine

P011B — Engine Coolant / Intake Air Temperature Correlation Fault

Severity: medium Safe to drive

What P011B means

After the engine sits for several hours, the engine coolant temperature (ECT) sensor and the intake air temperature (IAT) sensor should read nearly the same. If the ECM sees a large difference on a cold start, or the readings change in a way that doesn't make sense as the engine warms up, it sets P011B. The cause is most often one of the sensors, its connector or wiring, and less often a cooling system problem.

Symptoms

  • Check Engine light on
  • Rough or unstable idle
  • Hard starting when cold
  • Reduced fuel economy
  • Weaker performance
  • Erratic temperature readings on a scan tool

Possible causes

  1. Faulty engine coolant temperature sensor
  2. Faulty intake air temperature sensor
  3. Corroded connectors or damaged wiring to the sensors
  4. Poor ground or open/short in a sensor circuit
  5. Low coolant, trapped air or a stuck thermostat
  6. ECM software or internal fault (rare)

How to diagnose

  1. Scan for codes and review freeze frame data, noting any other temperature sensor codes
  2. Let the car cool for several hours, then compare ECT and IAT on a scan tool; they should be close
  3. Check coolant level and condition, and bleed air from the system if needed
  4. Inspect both sensor connectors and the harness for corrosion, chafing or moisture
  5. Measure sensor resistance with a multimeter and compare it to the spec for your vehicle
  6. Check the reference voltage and ground on the sensor circuits
  7. Check thermostat operation: the engine should warm up steadily and reach normal temperature
  8. If everything checks out, look for an ECM software update

Common fixes

  • Replace the engine coolant temperature sensor
  • Replace the intake air temperature sensor
  • Clean or replace connectors and repair damaged wiring
  • Top off coolant, bleed the system or replace the thermostat
  • Update ECM software or replace the ECM (last resort)

Questions and answers

What does P011B mean?

The ECM found that the coolant and intake air temperature sensor readings don't agree, even though they should be almost equal on a cold engine. A bad sensor or its wiring is usually the cause.

Can I drive with a P011B code?

Usually yes, but not for long. Wrong temperature data can make a cold engine run poorly and use more fuel, so have it checked soon.

How can I quickly check the sensors for P011B?

Let the engine cool completely and compare both sensor readings on a scan tool. If they differ a lot, test the suspect sensor's resistance and inspect its connector.

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.