Diagnostic Aids
Perform this test when instructed during QUICK TEST or other test step. This test is only intended to diagnose the following:
- Idle Air Control (IAC) valve.
- Idle Speed Control (ISC) valve.
- Harness circuits: IAC, ISC and VPWR.
- PCM.
CIRCUIT PIN IDENTIFICATION
| Circuit | PCM Pin No. | Wire Color |
|---|---|---|
| ISC | 81 | Light Blue |
- 1) DTC P0505: ISC Circuit Fault
DTC P0505 indicates a fault in IAC 2 circuit. Disconnect harness connector from Idle Speed Control (ISC). Measure resistance between ISC solenoid terminals. If resistance is about 10 ohms at 77°F (25°C), go to next step. If resistance is not about 10 ohms at 77°F (25°C), replace ISC. - 2) Check Power Supply
Turn ignition off. Disconnect ISC connector. Turn ignition on. Measure voltage between ground and ISC connector ignition power circuit (Blue/Yellow wire) at IAC 2 valve harness connector. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair Blue/Yellow wire from fuse panel. Restore all electrical connections and repeat QUICK TEST . - 3) Check ISC Circuit
Turn ignition off. Disconnect PCM and ISC and inspect harness connectors for damage. Measure resistance of ISC circuit (Light Blue wire) between PCM harness connector and ISC solenoid connector. Resistance should be less than 5 ohms. Also measure resistance of ISC circuit (Light Blue wire) between PCM connector terminal No. 81 and ground. Resistance should be greater than 10 k/ohms. If resistance measurements are as specified, go to next step. If either resistance measurement is not as specified, repair open or short to ground in Light Blue wire. Restore all electrical connections and repeat QUICK TEST .NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 10). No test procedures have been omitted. - 10) Check Idle Air Control (IAC) Valve
Turn ignition off. Disconnect Idle Speed Control (ISC) connector. Apply power and ground to ISC terminals. See Fig 1. If a click is heard when applying battery power to ISC valve, go to next step. If no click is heard when applying battery power to ISC valve, replace ISC valve. - 11) Check Power To ISC Valve
Turn ignition on. Turn A/C and blower motor on. Measure voltage between A/C relay wire at ISC harness (Blue/Yellow wire) and ground. If voltage is greater than 10 volts, go to next step. If voltage is 10 volts or less, go to TEST KM . - 12) Check IAC Valve Ground
Turn ignition off. Disconnect ISC harness connector. Measure resistance of ground circuit (Black wire) between ISC harness connector and ground. If resistance is less than 5 ohms, replace ISC. If resistance is 5 ohms or more, repair open circuit in Black wire.