What does it mean?
P1505 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Idle Charge Actuator Signal Low of Coil #1 .
Symptoms
- Check engine light on together with an unstable idle
- Idle hunting up and down or sagging below the normal speed
- Stalling at idle, worst with the A/C on or with an automatic in gear
- Rough running for the first minutes after a cold start
- Lazy return to idle when lifting off the throttle
- Engine falls back to a fixed emergency idle strategy
Likely causes
- Control wire for coil 1 shorted to ground where the insulation is rubbed through
- Partially shorted turns inside coil 1 of the idle actuator
- Moisture or oil inside the actuator connector bridging terminals
- Corroded supply or ground for the actuator, which makes the module read the drive signal as low
- Failed low-side driver in the module holding the circuit pulled down
- Damaged harness section where it passes a bracket or the hot side of the intake
How to fix it
- Note all stored codes and freeze frame data; companion idle codes point to a shared supply or ground
- Inspect the connector and harness routing for chafing and moisture ingress
- Unplug the actuator and check whether the control circuit still reads low with the ignition on; a low reading with the connector open means wiring or driver, not the actuator
- Measure coil 1 resistance and compare it with coil 2 as a reference; a much lower value indicates shorted turns
- Check the control wire for continuity to ground with both ends disconnected
- Replace the idle actuator if a coil is shorted, and repair the harness where insulation is damaged
- Carry out the idle relearn afterwards and confirm the duty cycle settles in live data