OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

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.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number1 / 1A

Possible causes

  • One sensor drifted high

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

Inspection / repair

  • Difficulty: easy
  • DIY: possible
  • Estimated cost: 40–250 €
  • Estimated time: 0.3–1.5 h
  • Component: ect sensor 1
  • Component: ect sensor 2
  • MIL / check engine light
  • emissions-relevant
  • drive cycle required

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication