P2AFF
Engine Coolant Temperature Sensor 4 Circuit High
Voltage on the engine coolant temperature 4 sensor signal line is above the expected window. Wire shorted to B+ or sensor open.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: easy
Symptoms
- Check engine light on
- Cooling fan runs constantly or not at all
- Cabin heater weak or excessively hot
- Possible long warm-up time or hard cold start
Common causes
Ordered by how often each turns out to be the cause.
- Signal wire shorted to B+Common
- Open sensorPossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Engine Coolant Temperature Sensor 4
- Wiring Harness
- ECM
P2AFF is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.