OBD-II code · Powertrain (generic)
P0126 Insufficient Coolant Temperature for Stable Operation
Coolant temperature stays below the value expected for stable engine operation. Almost always points to a thermostat stuck open or a sensor reading lower than the actual engine temperature.
Is it safe to drive with P0126?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyThermostat stuck open
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–2.5 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Thermostat, Coolant Temperature Sensor
Related codes
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.