DTC P0505: Idle Control System Failure

NOTE: For terminal identification, see TERMINAL IDENTIFICATION section. For circuit and wire color identification, see WIRING DIAGRAMS - NON-TURBO article.

Manufacturer does not provide component testing procedure without using scan tool. Ensure engine coolant temperature is 185-205°F (85-95°C). Place transmission in Park (A/T) or Neutral (M/T). Turn off all accessories except A/C. Ensure A/C clutch is operating when A/C system is on. Allow engine to idle. Go to next step.

Using scan tool, read Idle Air Control (IAC) position sensor step. See IAC POSITION SENSOR STEP SPECIFICATIONS table. If scan tool does not read as specified, replace IAC position sensor. If readings are as specified, go to next step.

IAC POSITION SENSOR STEP SPECIFICATIONS

A/C Switch Position

Standard Step Value

Off

2-25

Off To On

Increase From 10-70

⁽¹⁾

Increase From 5-50

⁽¹⁾	A/C On on 3000GT. Move gear selector lever to Drive position.

Disconnect IAC motor connector. Turn ignition switch to ON position. Check voltage between chassis ground and IAC motor connector terminals No. 2 and 5. If battery voltage does not exist on either circuit, repair wiring harness as necessary. If battery voltage exists on both circuits, go to next step.

Turn ignition switch to OFF position. Disconnect PCM connector and IAC motor connector. Ground specified PCM connector terminal and using DVOM, check continuity between chassis ground and specified IAC motor connector terminal. See PCM-TO-IAC MOTOR HARNESS CIRCUIT IDENTIFICATION table. If continuity does not exist, repair wiring harness as necessary. If continuity exists, go to next step.

PCM-TO-IAC MOTOR HARNESS CIRCUIT IDENTIFICATION

Application	PCM Terminal No.	IAC Motor Terminal No.
All Models	4	1
5		4
17		3
18		6

Test is complete. Intermittent problem may exist. Road test vehicle (if necessary) and attempt to duplicate conditions that caused original complaint. Recheck for DTCs. If no DTCs are displayed, go to INTERMITTENT DTCS .