Powertrain, generic (extended)

P2AFE Engine Coolant Temperature Sensor 4 Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Coolant sensors are NTC thermistors, so a signal from sensor 4 that is too low stands for an impossibly hot reading, usually a signal wire grounded or a shorted element. GM documents P2AFE for the 2.7 L turbo four (L3B) in its 2019 tables: the configurable temperature input system sets it when the resistance of the sensor 4 channel drops below about 41 Ω, corresponding to 150 °C, for 5 s within a 6 s window; Type B, so the MIL follows on the second trip. In bulletin 21-NA-149 GM names P2AFE as one consequence of engine harness chafing on 2019 to 2021 Silverado and Sierra 1500 trucks, the 2.7 L included. Because a hot reading is first taken at face value, the fans may run at full speed. P2AFF is the opposite fault, P2AFD the plausibility check.

Likely causes

Signal wire shorted to ground, for example by harness chafing
Internally shorted sensor
Faulty input in the engine control module

Symptoms

  • Check engine light after two trips
  • Cooling fans running at full speed
  • Implausibly high coolant temperature in live data

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–300
Time0.3–2 h

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

Parts involved

engine coolant temperature sensor 4wiring harnessecm

Related codes

P2AFFP2AFCP2AFDP2BB4P2184P01E5P2B2D

References: gsi.ext.gm.com, static.nhtsa.gov, ntn-snr.com.