P011A

Engine Coolant Temperature Sensor 1/2 Correlation

P011A is a generic OBD-II powertrain diagnostic trouble code: Engine Coolant Temperature Sensor 1/2 Correlation. It is logged by the engine control unit when the coolant monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P011A
Group
Powertrain
System
Coolant
Severity
Warning (MIL on)
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What P011A means

DTC P011A is set when the PCM detects a discrepancy in the voltage signals reported by two separate Engine Coolant Temperature (ECT) sensors — ECT Sensor 1 and ECT Sensor 2 — that exceeds a programmed correlation threshold. This code only applies to vehicles equipped with multiple ECT sensors, a configuration common on modern engines that use one sensor near the thermostat outlet to control fuelling and timing, and a second sensor elsewhere in the cooling circuit (such as near the radiator inlet) for cooling fan control or OBD monitoring. Under normal operation, the PCM expects the readings from the two sensors to remain within a predictable relationship relative to each other at any given time. When the difference between the sensors exceeds the calibrated limit — even if each individual sensor appears to be within its own voltage range — the PCM stores P011A. Typical causes include a failing sensor whose resistance has drifted, low coolant level exposing one sensor to air rather than liquid, an air pocket in the cooling system producing a false reading, or a faulty thermostat that creates an abnormal temperature gradient between the two measurement points. Cooling fan operation, temperature gauge accuracy, and cold-start enrichment can all be adversely affected while this code is active.

Common causes

Most-frequently reported root causes when P011A is logged.

  • 1
    Defective ECT Sensor 1 or Sensor 2 with drifted resistance characteristics
  • 2
    Low engine coolant level exposing one of the sensors to air rather than liquid coolant
  • 3
    Air pocket or air lock in the cooling system creating a false temperature differential
  • 4
    Faulty thermostat stuck open or closed, producing an abnormal temperature gradient between sensor locations
  • 5
    Open, shorted, or high-resistance wiring in either ECT sensor circuit
  • 6
    Corroded or loose sensor connector causing voltage offset on one sensor channel
  • 7
    PCM software fault or internal failure causing incorrect correlation calculation

Symptoms drivers notice

Malfunction Indicator Lamp (MIL / check engine light) illuminated
Inaccurate or erratic coolant temperature gauge reading
Incorrect or excessive cooling fan operation — fan may run too early, too late, or continuously
Rich or lean cold-start mixture due to inaccurate ECT input to fuelling calculations
Rough idle or hesitation during engine warm-up phase
Reduced fuel economy caused by prolonged cold-start enrichment if the PCM perceives the engine as remaining cold

How to diagnose P011A

A typical diagnostic flow when this code is present.

  1. 1
    Verify engine coolant is filled to the correct level with the proper specification coolant; purge any air pockets by running the engine with the heater on full and the cap off until the thermostat opens
  2. 2
    Confirm the thermostat, water pump, radiator, and cooling fans are operating correctly before proceeding — a cooling system that cannot reach or maintain normal operating temperature will prevent an accurate correlation diagnosis
  3. 3
    Connect a scan tool and compare live ECT Sensor 1 and Sensor 2 readings simultaneously from cold start through full warm-up; the difference should narrow as the engine reaches operating temperature
  4. 4
    Visually inspect both ECT sensor connectors and wiring harnesses for corrosion, backed-out terminals, or heat damage
  5. 5
    Disconnect each sensor individually and measure its resistance with a DVOM at known coolant temperatures; compare readings to the manufacturer's temperature-resistance curve in the service manual
  6. 6
    Test each sensor's signal circuit and ground circuit continuity from sensor connector to PCM; repair any high-resistance connections found
  7. 7
    If all components test within specification, consult Technical Service Bulletins for PCM calibration updates that adjust the correlation threshold, or consider PCM replacement as a last resort

Vehicles where we've handled P011A

Platforms in our catalogue with confirmed P011A coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Can I still drive safely with P011A active?

Short-term driving is generally safe, but the engine's cooling fan control and fuelling accuracy are compromised. If the temperature gauge reads abnormally or the engine shows signs of overheating, stop immediately. Have the code diagnosed before extended driving.

Does P011A always mean one of the ECT sensors has failed?

No. The code indicates a correlation problem — both sensors may be individually within voltage range, but they are disagreeing with each other. Low coolant, an air pocket, or a stuck thermostat can cause this code without either sensor having failed outright.

How is P011A different from P0115 or P0116?

P0115 and P0116 are single-sensor codes flagging a range or circuit fault on ECT Sensor 1. P011A is a two-sensor correlation code — it requires the vehicle to have a second ECT sensor and specifically flags a mismatch between the two readings.

Will fixing a coolant air pocket resolve P011A?

If an air pocket is causing one sensor to read incorrectly (sensing air instead of liquid coolant), properly bleeding the cooling system may resolve the code. This is a common and easily overlooked cause, particularly after coolant system repairs or replacement.

Disabling P011A in software

RaceTune can permanently disable P011A — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECU families we can disable P011A on

We hold the DaVinci A2L disable definitions for these families, so the exact P011A path and mask addresses are mapped. verified marks a confirmed disable definition. We support many more — upload your file and our identifier will match it automatically.

  • Bosch EDC17C50 verified
  • Bosch EDC17C56 verified

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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