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P011A

Engine Coolant Temperature Sensor 1/2 Correlation

ECT sensors 1 and 2 readings disagree beyond plausible limits — typically near startup both should match within tolerance.

  • Check engine light: Yes
  • Emissions related: Yes
  • Repair difficulty: easy

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

Common causes

Ordered by how often each turns out to be the cause.

  • One sensor driftedCommon

Parts involved

  • ECT Sensor 1
  • ECT Sensor 2

P011A is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.