P00B5
Radiator Coolant Temperature Sensor Circuit Intermittent/Erratic
Cooling / temperature sensor
Generic OBD-II
High
What it means
P00B5 means the signal from the radiator coolant temperature sensor is cutting in and out or jumping erratically. This sensor (separate from the main engine coolant sensor) helps the ECM manage cooling-fan and thermal strategy. The cause is almost always an intermittent wiring or connector fault or a failing sensor — not the fan or relay itself.
High
Can I keep driving? Usually safe for short trips, but watch the temperature gauge — an erratic radiator coolant sensor can upset cooling-fan control, so don't ignore any overheating.
Common symptoms
What you'll notice
- Check-engine light on
- Cooling fans running erratically or at the wrong time
- Fluctuating or implausible temperature readings
- Occasional hard cold start
Common causes
Most likely first
- Faulty radiator coolant temperature sensorLikely
- Intermittent open or short in the sensor wiringCommon
- Loose or corroded sensor connectorCommon
- Rarely, an ECM/PCM faultLess often
How to diagnose & fix
Work through it in order
- Wiggle-test the sensor connector and harness while watching live data for the signal to drop out.
- Inspect the connector for corrosion or spread terminals and reseat it.
- Measure sensor resistance across a temperature range; replace if it reads erratic or out of spec.
- If wiring and sensor are good, suspect the ECM. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P00B5?+
Short trips are usually fine, but because this sensor can influence fan operation, keep an eye on the temperature gauge and stop if the engine overheats.
Can I just clear P00B5?+
You can, but an intermittent fault like this typically returns; the fix is finding the loose connection or failing sensor.
Related codes
Often seen with P00B5
Read & clear P00B5 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX