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DTC P0505 - Idle Control System Malfunction

NOTE: For terminal identification, see TERMINAL IDENTIFICATION in SELF-DIAGNOSTICS section. For circuit and wire color identification, see WIRING DIAGRAMS - 2.4L article.
  1. Ensure engine coolant temperature is less than 68°F (20°C). Using a stethoscope, listen for operating sound of Idle Air Control (IAC) motor when ignition switch is placed in ON position. If operating sound can be heard, go to next step. If no operating sound can be heard, go to step  5 .
  2. Turn ignition off. Connect Test Harness (MB991348) between IAC motor and connector. Check voltage between ground and test harness terminals No. 2 and 4. Voltage should momentarily go from 1.5-4.0 volts to less than one volt or more than 4.5 volts right after ignition switch is turned on. If voltage is as specified on both circuits, replace PCM. If voltage is not as specified, go to next step.
  3. Disconnect IAC motor connector. Check voltage between ground and IAC motor connector terminals No. 1, 2 and 4. Voltage should be 4.8-5.2 volts. Check continuity between ground and IAC motor connector terminal No. 3. Go to next step.
  4. If voltage is as specified and continuity exists, check IAC motor connector. If IAC motor connector is okay, replace IAC motor. If voltage is not as specified or continuity does not exist, check IAC motor connector and wiring harness between PCM and IAC motor connector. If connector and wiring are okay, replace PCM.
  5. Connect Test Harness (MB991348) between IAC motor and connector. Turn ignition switch on. Check voltage between ground and test harness terminal No. 5. Voltage should be 2 volts or more to 0-1 volt (momentarily after ignition is turned on). Check voltage between ground and test harness terminal No. 6. Voltage should be 4 volts or more to 0-1 volt (momentarily after ignition is turned on). If voltages are as specifed, replace IAC motor. If voltages are not as specified, check harness connectors and wiring between PCM and IAC motor. If connectors and wiring are okay, replace PCM.
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