OBD-II code · Powertrain (generic)
P0666 Control Module Internal Temperature Sensor A Circuit
A general circuit fault on the ECU's internal temperature sensor A - the sensor that monitors module operating temperature for thermal protection.
Is it safe to drive with P0666?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyInternal sensor fault
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 2–6 h
- Emissions test
- Usually unaffected
- Parts involved
- Ecu Internal Temperature Sensor A
Related codes
- P06ABControl Module Internal Temperature Sensor B Circuit
- P0663Intake Manifold Tuning Valve Control Circuit Open Bank 2
- P0664Intake Manifold Tuning Valve Control Circuit Low Bank 2
- P0665Intake Manifold Tuning Valve Control Circuit High Bank 2
- P0667Control Module Internal Temperature Sensor A Range or Performance
- P0668Control Module Internal Temperature Sensor A Circuit Low
- P0669Control Module Internal Temperature Sensor A Circuit High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.