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P00B6

Radiator Coolant Temperature/Engine Coolant Temperature Correlation

Difference between radiator outlet and engine coolant temperatures is implausible — typically indicates a stuck thermostat.

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

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.

  • Thermostat stuck open (slow warm-up)Common

Parts involved

  • Thermostat
  • Radiator Coolant Temp Sensor
  • Engine Coolant Temp Sensor

P00B6 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.