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DTC P0505-A: Idle Air Control Motor Circuits

NOTE: For connector terminal ID, see CONNECTOR IDENTIFICATION . For wiring diagram, see WIRING DIAGRAMS article.
  1. Using scan tool, read Diagnostic Trouble Codes (DTCs). If scan tool display GLOBAL GOOD TRIP is equal to zero, go to step  4. If scan tool display GLOBAL GOOD TRIP is not equal to zero, go to next step.
  2. Using scan tool, read FREEZE FRAME data. Ensure hex code matches DTC on scan tool. Hex code should be 19. If DTC matches hex code on scan tool, go to next step. If DTC does not match hex code on scan tool, repair DTC using FREEZE FRAME data. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES .
  3. Read FREEZE FRAME data on scan tool. Try to duplicate conditions identified on scan tool. Pay particular attention to code set conditions: engine RPM, coolant temperature and engine load. Using scan tool, observe GLOBAL GOOD TRIP counter. If GLOBAL GOOD TRIP counter changed to zero, operate vehicle for one good trip, then erase DTCs. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If GLOBAL GOOD TRIP counter does not change to zero, go to next step.
  4. Turn ignition off for 10 seconds. Start engine. Allow engine to idle for 20 seconds. If engine will not idle, hold throttle open slightly to keep engine running. Using scan tool, actuate Idle Air Control (IAC) motor to 1400 RPM. Release throttle. If engine speed is 1300-1500 RPM, go to next step. If engine speed is not 1300-1500 RPM, go to step  10.
  5. Using scan tool, actuate IAC motor to 900 RPM. If engine speed is 800-1000 RPM, go to next step. If engine speed is not 800-1000 RPM, go to step  10.
  6. Condition to set trouble code is not present at this time. IDLE AIR CONTROL MOTOR CIRCUITS DTC sets if Powertrain Control Module (PCM) senses a short to ground or battery voltage on any 4 IAC driver circuits for 2.75 seconds while IAC motor is active. Possible causes are: driver circuit shorted to ground, driver circuit shorted to battery, driver circuits shorted together, failed PCM, shorted IAC motor, faulty connections or wiring.
  7. Inspect all related wiring and connectors and repair as necessary. If no problems were found with wiring and connectors, go to next step. If related wiring and connectors were repaired, perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES .
  8. Start engine. Using scan tool, actuate IAC motor wiggle test. Idle speed should raise and lower with scan tool display. If IAC motor operates properly, go to next step. If IAC motor does not operate properly, go to step  10.
  9. Wiggle wiring harness from IAC motor to Powertrain Control Motor (PCM). If IAC motor stopped operating at any time, repair wiring harness as necessary where wiggling caused problem to appear. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If IAC motor did not stop operating at any time, stop IAC motor wiggle test. See INACTIVE TROUBLE CODE CONDITION  under SELF-DIAGNOSTICS. Test is complete. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES .
    NOTE: For remaining test steps, see IAC DRIVER CIRCUIT ID  table for IAC motor connector wire color identification.
  10. Using scan tool, stop all actuation tests. Turn ignition off. Disconnect IAC motor connector. Using an ohmmeter, check resistance of IAC driver No. 1 circuit between IAC motor connector and ground. If resistance is less than 5 ohms, repair short to ground in driver No. 1 circuit. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If resistance is more than 5 ohms, go to next step.
  11. Check resistance of IAC driver No. 2 circuit between IAC motor connector and ground. If resistance is less than 5 ohms, repair short to ground in driver No. 2 circuit. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If resistance is more than 5 ohms, go to next step.
  12. Check resistance of IAC driver No. 3 circuit between IAC motor connector and ground. If resistance is less than 5 ohms, repair short to ground in driver No. 3 circuit. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If resistance is more than 5 ohms, go to next step.
  13. Check resistance of IAC driver No. 4 circuit between IAC motor connector and ground. If resistance is less than 5 ohms, repair short to ground in driver No. 4 circuit. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If resistance is more than 5 ohms, go to next step.
  14. Start engine and idle. Using a voltmeter, check voltage of IAC motor connector driver No. 1 circuit. If voltage is more than 5 volts at any time, go to next step. If voltage is 5 volts or less at any time, go to DTC P0505-B: IDLE AIR CONTROL MOTOR CIRCUITS .
  15. Check voltage of IAC motor connector driver No. 2 circuit. If voltage is more than 5 volts at any time, go to next step. If voltage is 5 volts or less at any time, go to DTC P0505-C: IDLE AIR CONTROL MOTOR CIRCUITS .
  16. check voltage of IAC motor connector driver No. 3 circuit. If voltage is more than 5 volts at any time, go to next step. If voltage is 5 volts or less at any time, go to DTC P0505-D: IDLE AIR CONTROL MOTOR CIRCUITS .
  17. check voltage of IAC motor connector driver No. 4 circuit. If voltage is more than 5 volts at any time, go to next step. If voltage is 5 volts or less at any time, go to DTC P0505-E: IDLE AIR CONTROL MOTOR CIRCUITS .
  18. Turn ignition off. Disconnect PCM connector. Inspect PCM connector for damaged or pushed out terminals. Repair as necessary. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If connector is okay, go to next step.
  19. Using an ohmmeter, check resistance between the following circuits at IAC motor connector. Record resistance readings.
    • IAC motor connector driver No. 1 and driver No. 2
    • IAC motor connector driver No. 1 and driver No. 3
    • IAC motor connector driver No. 1 and driver No. 4
  20. If resistance between any 2 wires was less than 5 ohms, repair those wires for shorting together. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If resistance between all pairs of wires was 5 ohms or more, go to next step.
  21. Using an ohmmeter, check resistance between the following wires at IAC motor connector. Record resistance readings.
    • IAC motor connector driver No. 2 and driver No. 3
    • IAC motor connector driver No. 2 and driver No. 4
  22. If resistance between any 2 wires was less than 5 ohms, repair those wires for shorting together. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If resistance between all pairs of wires was 5 ohms or more, go to next step.
  23. Using an ohmmeter, check resistance between the following wires at IAC motor connector. Record resistance readings.
    • IAC motor connector driver No. 3 and driver No. 4
  24. If resistance between wires was less than 5 ohms, repair wires for shorting together. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If resistance between wires was 5 ohms or more, replace IAC motor. Perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES .
IAC DRIVER CIRCUIT ID

Application Wire Color
Driver No. 1 Gray/Red
Driver No. 2 Yellow/Black
Driver No. 3 Brown/White
Driver No. 4 Violet/Black
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