Powertrain, generic (extended)

P2D2C Engine Coolant Temperature Measurement System - Multiple Sensor Correlation

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Engines with split or map-controlled cooling carry several coolant sensors, for example at head, block, inlet, outlet, radiator and heater core. After a cold soak all should read alike; P2D2C reports that the set as a whole disagrees and the module cannot single out one sensor. No manufacturer documents P2D2C publicly. GM's 2025 tables do the comparison under P0116 instead: once per valid cold start the coolant sensor is checked against two others from a configurable list that also includes oil, intake and outside air, Type B over two trips. CARB demands rationality checks of the ECT sensor and an approved plan for engines that read two sensors placed in different coolant loops. Warm-up enrichment and thermostat diagnosis may suffer.

Likely causes

One coolant sensor in the set has drifted
Uneven soak, e.g. block heater or short stop, misread as a fault
Low coolant or air leaving one sensor dry
Corroded terminal shifting one reading

Symptoms

  • Check engine light
  • Temperature gauge or fan behaviour unusual
  • Rough cold running or higher fuel use when warming up

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–400
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

engine coolant temperature sensor 1engine coolant temperature sensor 2ecm

Related codes

P0116P011AP2183P00B6P011BP012F

References: gsi.ext.gm.com, law.cornell.edu.