What does it mean?
P1509 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Bypass Air Solenoid 2 Circuit Malfunction .
Symptoms
- Check engine light on with an uneven idle
- Idle sits low and dips further when a load is applied
- Stalling at idle or when coasting to a stop
- Poor cold-start behaviour with a slow warm-up idle
- Engine speed does not rise as expected with the A/C on
- No audible click from the solenoid when it should be commanded
Likely causes
- Open or shorted winding in bypass air solenoid 2
- Corroded or wet connector at the solenoid
- Broken or chafed control wire between the module and the solenoid
- Carbon or varnish blocking the bypass passage so the solenoid cannot deliver the requested airflow
- Missing supply voltage from a blown fuse or a poor relay contact
- Failed module output driver
How to fix it
- Command the solenoid with a bidirectional scan tool and listen or feel for it operating
- Measure the solenoid winding resistance and compare it with the first bypass solenoid
- Check for supply voltage and a good ground at the solenoid connector with the ignition on
- Check the control wire back to the module for continuity and for a short to ground
- Remove the solenoid and clean the bypass passage of carbon
- Replace bypass air solenoid 2 if it is electrically open or mechanically stuck
- Recheck idle in live data and relearn the idle values after the repair