P2AFFEngine Coolant Temperature Sensor 4 Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P2AFF reports an excessive sensor 4 signal. For an NTC thermistor that means an implausibly cold reading, mostly from an open circuit, an unplugged connector or a line shorted to voltage. GM's 2019 tables for the 2.7 L L3B set P2AFF once the resistance rises above roughly 355 kΩ, equal to −60 °C, for 5 s in a 6 s window, with an engine run time above 10 s among the enabling conditions; Type B with MIL after two trips. Oddly, the same GM table names the radiator coolant sensor in the P2AFF row while assigning P2AFE to coolant sensor 4, but both channels share the same threshold. GM bulletin 21-NA-149 also lists P2AFF for chafed engine harnesses on its 1500 pickups. The engine computer then works with a substitute value. P2AFE is the short-to-ground case.
- What you may notice
- Check engine light after two trips
- Implausibly cold coolant temperature in live data
- Thermal management running on a default value
- Likely causes
- LikelyOpen signal wire or unplugged connector
- PossibleChafed engine harness
- PossibleSensor element open internally
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.