OBD-II code · Powertrain (generic)
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.
Is it safe to drive with P00B4?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySignal wire open
- Less likelyConnector pins corroded - high contact resistance
- Less likelySupply wire pinched against B+ source
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–1.5 h
- Emissions test
- Likely to fail
- Parts involved
- Radiator Coolant Temp Sensor, Sensor Wiring
Related codes
- P00B1Radiator Coolant Temperature Sensor Circuit
- P00B2Radiator Coolant Temperature Sensor Circuit Range/Performance
- P00B3Radiator Coolant Temperature Sensor Circuit Low
- P00B5Radiator Coolant Temperature Sensor Circuit Intermittent/Erratic
- P00B6Radiator Coolant Temperature/Engine Coolant Temperature Correlation
- P00B7Engine Coolant Flow Low/Performance
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.