Engine Coolant Bypass Valve A Stuck Closed
The coolant bypass valve A is stuck closed. Coolant cannot bypass the radiator during warm-up so warm-up takes longer and emissions in the warm-up phase rise.
Affected components
- Coolant bypass valve a
- Thermostat housing
Common causes
- High likelihood: Valve seized closed by debris
- Medium likelihood: Actuator linkage jammed in closed position
- Low likelihood: Carbon or debris buildup preventing free movement
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.