P0126 fault code: what it means

P0126: Coolant temperature too low for stable operation. Usually the thermostat.

Engine and gearbox (powertrain) · Minor

Usual causes, most likely first

1. thermostat stuck open
2. ECT sensor

P0126 by make

Not sure what P0126 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.