Engine Management

Scan Tool 25 (MIL 25):

Trouble Code Number
- Scan tool 25
- General Scan Tool P0505
- MIL 25

Fault Message
- Idle Air Control (IAC) Motor Circuits

Background
- The idle air control (IAC) stepper motor is used to prevent the engine from stalling at idle.
- With the throttle plate completely closed, placing a load on the engine (A/C or power steering operation) might cause the engine to stall or run rough.
- As the PCM anticipates load, it operates the IAC motor, opening the throttle bypass passage and allowing more air into the intake manifold.
- Malfunction of this system could cause rough idle and unstable emissions.
- The PCM cannot detect an open circuit or determine if the stepper motor is stuck in one position.

Range of Check
- Battery voltage: 10 V or more
- Ignition switch: ON

Set Condition
- A short or open circuit condition is detected in a motor circuit for 3 seconds.

Probable Cause
- Driver circuit shorted to ground
- Driver circuit shorted to battery
- Driver circuits shorted to together
- PCM failed
- Shorted IAC motor