P1258critical severityPowertrain
Engine Coolant Overtemperature Protection Mode Active
on 2002 Chevrolet Impala 3.4L V6 · FWD
What this code means
The PCM has activated engine protection mode due to excessive coolant temperature. The PCM may reduce power output, disable cylinders, or limit RPM to prevent engine damage from overheating. This is a serious code that requires immediate attention.
Symptoms
- Reduced Engine Power message
- Engine overheating
- Temperature gauge in red zone
- Loss of power
- Engine may shut down
- A/C system disabled
Common causes
- Low coolant level
- Failed water pump
- Stuck closed thermostat
- Blocked radiator
- Faulty coolant temperature sensor
- Head gasket failure
- Cooling fan failure
- Collapsed radiator hose
Diagnostic steps
- Check coolant level immediately
- Inspect for coolant leaks
- Test thermostat operation
- Check water pump for flow
- Test cooling fans
- Inspect radiator for blockage
- Pressure test cooling system
- Check head gasket (combustion gas test)
Repair notes
Do not continue driving. Check coolant level and look for leaks immediately. Continued overheating will cause severe engine damage including head gasket failure and warped heads.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1