What does it mean?
P1506 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Idle Air Control Valve Circuit Short to B+ .
Symptoms
- Check engine light on with a noticeably high idle
- Idle stuck up around fast-idle speed even when the engine is hot
- Car creeps strongly in gear and engine braking feels weak
- Higher fuel consumption around town
- Idle does not respond when loads are switched on or off
- Occasional stalling or a flare when the circuit breaks down intermittently
Likely causes
- Control wire chafed against a permanently live conductor or a positive stud
- Corrosion or debris inside the valve connector bridging the supply pin to the control pin
- Internal short between the winding and the supply side of the valve
- Melted or crushed harness section routed close to a hot exhaust part or an alternator feed
- Incorrectly spliced accessory wiring tapped into the idle control circuit
- Failed driver in the module that no longer pulls the circuit down
How to fix it
- Confirm the high-idle complaint and check the commanded idle position in live data
- Unplug the valve and, with the ignition on and no command, measure the control pin to ground; battery voltage there points to a short to positive in the harness
- If the voltage disappears when the module connector is unplugged as well, suspect the module driver
- Inspect the harness where it runs alongside power feeds and near heat sources for melted insulation
- Check the connector for green corrosion and pin-to-pin leakage with a resistance measurement
- Repair the damaged harness section with proper insulation and routing
- Replace the idle air control valve only if it shows internal leakage between the supply and control terminals