P2CF1

Auxiliary Thermostat B Stuck Open

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$17–67 (est.)

Symptoms

Long engine warm-up
Increased fuel consumption
Reduced engine temperature at idle
Insufficient interior heating in winter
Check Engine Light Is On

Causes

Mechanical wear of the thermostat
Thermostat valve stuck
Debris getting into the thermostat mechanism
Electrical problems (for electronic thermostats)
Corrosion of thermostat components

How to Fix

Cooling system diagnostics
Checking the functionality of thermostat B
Replacing a faulty thermostat
Flushing the cooling system
Reset error and test drive

Related codes

P0128 P0597 P0599