OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

P00B5

Radiator Coolant Temperature Sensor Circuit Intermittent/Erratic

Intermittent signal from radiator coolant temperature sensor. 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.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number– / B5

Possible causes

  • Connector loose or corroded high
  • Connector with intermittent contact under vibration low
  • Harness routed against vibrating component low

Inspection / repair

  • Difficulty: easy
  • DIY: possible
  • Estimated cost: 30–200 €
  • Estimated time: 0.3–1 h
  • Component: radiator coolant temp sensor
  • Component: sensor wiring
  • MIL / check engine light
  • emissions-relevant
  • drive cycle required

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication