P00B4
Radiator Coolant Temperature Sensor Circuit High
Radiator coolant temperature sensor signal voltage above expected range. The engine coolant temperature sensor feeds warm-up enrichment, fan control and closed-loop entry — a stuck-cold reading keeps the engine in open loop and rich forever.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: easy
Common causes
Ordered by how often each turns out to be the cause.
- Signal wire openCommon
- Connector pins corroded - high contact resistanceLess likely
- Supply wire pinched against B+ sourceLess likely
Parts involved
- Radiator Coolant Temp Sensor
- Sensor Wiring
P00B4 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.