Powertrain, generic (extended)

P2C38 Cylinder Head Temperature Sensor B Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

A cylinder head temperature sensor is an NTC thermistor seated in the head metal that tells the module how hot the engine really is, even without coolant. P2C38 is the general circuit fault of a second such sensor, B: the signal is open, shorted or otherwise unusable, without separating low from high (P2C3A/P2C3B do that, P2C39 judges plausibility). Ford uses it on the 2025 Explorer and Aviator with 2.3 L or 3.0 L EcoBoost: TSB 24-2393 (built until 15 Oct 2024) describes an over-temperature warning with P1299 plus P2C38 or P2C39 although fan and coolant are fine, and cures it by reprogramming the PCM. For sensor A Ford's 2024 summary flags below 0.244 V or above 4.96 V after 5 s. CARB treats head temperature sensors used for emission control like coolant sensors.

Likely causes

PCM software causing false faults (Ford 2025 Explorer/Aviator, TSB 24-2393)
Loose or corroded connector at the head sensor
Failed head temperature sensor B
Heat-damaged or chafed wiring near the cylinder head

Symptoms

  • MIL and engine over-temperature warning
  • Fail-safe cooling mode with reduced power possible
  • Temperature warning even though coolant level and fan are fine

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–600
Time0.5–3 h

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

Parts involved

cylinder head temperature sensor bwiring harnessecm

Related codes

P2C39P2C3AP2C3BP2C3CP2C3DP017A

References: static.nhtsa.gov, fordservicecontent.com, law.cornell.edu.