What does it mean?
P1510 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: ISC Solenoid Valve Signal No. 1 Circuit Malfunction (low input) .
Symptoms
- Check engine light on with an unstable or low idle
- Engine stalls when decelerating to a stop
- No idle-up when the A/C, blower or steering load is applied
- Rough idle and a hesitation just off closed throttle
- Idle speed varies between starts without an obvious reason
- Automatic transmission engagement feels harsh because idle is out of range
Likely causes
- Short to ground on the signal 1 control wire
- Open supply to the solenoid, which the module interprets as a low signal
- Water or oil in the solenoid connector bridging the terminals
- Shorted turns inside the solenoid winding for that channel
- Corroded ground point shared by the idle control circuit
- Failed module driver stage on that output
How to fix it
- Record freeze frame and check for parallel codes on the other signal channels, which usually means a shared supply or ground problem
- Unplug the solenoid and check whether the signal circuit still reads low with the ignition on
- Measure the winding resistance of the affected channel and compare it with the other channels
- Check supply voltage and ground quality at the connector, including a voltage drop test on the ground side
- Check the control wire for a short to ground with both ends disconnected
- Clean the throttle body and bypass passage while the solenoid is off, then refit it
- Replace the idle speed control solenoid if the affected winding is out of specification, then relearn idle