What does it mean?
P1643 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Supercharger Bypass Valve Actuator Control System - Stuck Closed .
Symptoms
- MIL on, sometimes with reduced power or limp mode
- Boost present when it should not be: surging, rough or hunting idle
- Poor part-throttle drivability and hesitation on light acceleration
- Supercharger whine or whistle at light throttle and cruise
- Higher fuel consumption and elevated intake air temperature on live data
Likely causes
- Bypass valve blade or shaft seized with carbon and oil deposits
- Torn or leaking vacuum actuator diaphragm that can no longer pull the valve open
- Cracked, collapsed or disconnected vacuum hose to the actuator
- Bypass control solenoid failed, clogged or not switching vacuum
- Vacuum reservoir or check valve not holding vacuum on part throttle
- Bent or seized linkage between actuator and valve
- Open or shorted control circuit and connector at the bypass solenoid
How to fix it
- Inspect the bypass valve and linkage with the engine off and move it by hand; it should travel freely and return
- Apply vacuum to the actuator with a hand pump; it must hold vacuum and stroke the valve fully
- Check the vacuum hose, reservoir and check valve for cracks, collapse and leaks
- Test the bypass solenoid: measure coil resistance and command it with the scan tool while feeling for a click and checking vacuum passes through
- Clean carbon from the valve seat and shaft if the blade drags
- Repair the wiring and connector between the solenoid and the module, checking for open and shorted circuits
- Replace the actuator or the bypass valve assembly if it still will not open, then clear and road test