Diagnostic Aids
Perform this test only when instructed by QUICK TEST, or directed here by a driveability symptom. This test is intended to diagnose only the following components or circuits:
- Harness circuits (VPWR and IAC)
- IAC solenoid
- ECA
To prevent replacing good components, check the following non-EEC areas for faults:
- Vacuum tank leaks
- Vacuum hose leaks
1) Code 81: Check IAC Solenoid Resistance Code 81 indicates IAC solenoid output voltage did not change when IAC was activated during KOEO SELF-TEST. Possible causes for this fault are as follows:
- IAC circuit open
- IAC shorted or disconnected
- ECA output driver open or grounded
Turn ignition off and wait 10 seconds. Set DVOM on 200-ohm scale and disconnect IAC solenoid connector from harness. Measure resistance between IAC and VPWR circuits of solenoid at solenoid terminals. If resistance is 50-100 ohms, go to next step. If resistance is NOT 50-100 ohms, replace solenoid and rerun QUICK TEST.
2) Check Voltage Of VPWR Circuit With Key On Engine Off (KOEO), disconnect IAC solenoid. Set DVOM on 20-volt scale. Measure voltage between VPWR circuit of IAC solenoid vehicle harness connector and battery negative post. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, reconnect IAC solenoid, repair open circuit in harness and rerun QUICK TEST.
3) Check Continuity Of IAC Solenoid Circuit Turn ignition off and wait 10 seconds. Disconnect 60-pin ECA connector. Inspect pins for corrosion or damage, and service as necessary. Install breakout box, leaving ECA and IAC solenoid disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 32 at breakout box and IAC solenoid vehicle harness connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit. Remove breakout box, reconnect all components and repeat QUICK TEST.
4) Check For Short To Ground Turn ignition off and wait 10 seconds. With breakout box installed and ECA disconnected, set DVOM on 200-k/ohm scale. Disconnect IAC solenoid. Measure resistance between test pin No. 32 and test pins No. 40, 46 and 60 at breakout box. If resistance is greater than 100 k/ohms, go to next step. If resistance is less than 100 k/ohms, repair short circuit, reconnect components and repeat QUICK TEST.
5) Check IAC Circuit For Short To Power Turn ignition off and wait 10 seconds. With breakout box installed and ECA disconnected, set DVOM on 200-k/ohm scale. Disconnect IAC solenoid. Measure resistance between test pin No. 32 and test pins No. 37 and 57 at breakout box. If resistance is greater than 100 k/ohms, replace ECA. Remove breakout box, reconnect components and repeat QUICK TEST. If resistance is less than 100 k/ohms, repair short circuit, reconnect components and retest. If fault is still present, replace ECA.
6) Check Front & Rear Intake Air Valves With ignition off, disconnect vacuum lines from both intake air valves. Check each air valve with a vacuum pump. Apply 10 in. Hg vacuum. If both valves hold vacuum, go to next step. If valves do not hold vacuum, replace valve(s) as necessary. Reconnect all components and rerun QUICK TEST.
7) Check Operation Of Both Intake Air Valve Systems With ignition off, apply 10 in. Hg to each air valve. If both valves and mechanical linkage move in response to the applied vacuum, go to next step. If valves and linkage are faulty, service as necessary and rerun QUICK TEST.
8) Check Vacuum To Both Intake Air Valves With ignition off, check vacuum lines from air valves to IAC solenoid. Inspect lines for damage or blockage. If vacuum lines are okay, go to next step. If vacuum lines are damaged or blocked, service as necessary and retest.
9) Check Vacuum Source To IAC Solenoid Disconnect IAC solenoid vacuum supply hose from intake manifold. Start engine and check vacuum at disconnected manifold hose. If vacuum is present at hose, replace IAC solenoid and rerun QUICK TEST. If vacuum is not present, check supply hose to IAC solenoid. Service as necessary and rerun QUICK TEST.