Powertrain, generic (extended)

P2AFC Engine Coolant Temperature Sensor 4 Circuit

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

P2AFC is the general circuit code for a fourth engine coolant temperature sensor. Engines with split cooling, electric pumps or separate head, block, radiator and heater circuits carry several such sensors, and how they are numbered is up to each maker. No manufacturer documents a set condition for P2AFC publicly; for the 2019 L3B 2.7-litre engine GM instead assigns separate low and high codes to this sensor (P2AFE, P2AFF). Supplier NTN-SNR describes P2AFC in its coolant sensor catalogue as an electrical defect in the circuit of sensor 4. CARB requires coolant temperature inputs to be monitored for broken circuits and for values outside their range. Expect an open line, a loose plug or a failed NTC element; the engine computer then falls back on a substitute value.

Likely causes

Open wire or loose connector at sensor 4

Failed NTC element in sensor 4

Faulty input stage in the engine control module

Symptoms

Check engine light on
Cooling fans running more than usual on substitute value
Thermal management in default mode

Repair estimate

DifficultyEasyDIY possible

Parts and labour€30–250

Time0.3–1.5 h

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

Parts involved

engine coolant temperature sensor 4wiring harnessecm

References: law.cornell.edu, ntn-snr.com, gsi.ext.gm.com.