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Diagnostic Aids

Perform this test only when instructed by QUICK TEST or directed here by a driveability symptom. This test is only intended to diagnose:

To prevent replacing good components, check the following non-EEC areas for faults:

Fig 1: IMRC Circuit
G93A40758

1) Code 551: Check IMRC Solenoid Resistance  Code 551 indicates IMRC solenoid output voltage did not change when IMRC was activated during KOEO SELF-TEST. Possible causes for this fault are:

Turn ignition off. Disconnect IMRC solenoid wiring harness connector. Measure resistance between IMRC solenoid terminals. If resistance is not 50-100 ohms, replace solenoid and repeat QUICK TEST. If resistance is 50-100 ohms, go to step 2).

2) Check Voltage Of VPWR Circuit  Turn ignition on. Measure voltage between VPWR terminal of IMRC solenoid wiring harness connector and negative battery terminal. If voltage is more than 10.5 volts, go to step 3). If voltage is 10.5 volts or less, repair open circuit and repeat QUICK TEST.

3) Check Continuity Of IMRC Solenoid Circuit  Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 32 at breakout box and IMRC terminal of IMRC solenoid wiring harness connector. If resistance is 5 ohms or less, go to step 4). If resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST.

4) Check IMRC Circuit For Short To Ground  Turn ignition off. Measure resistance between test pin No. 32 and test pins No. 40, 46 and 60. If resistance is 100,000 ohms or more, go to step 5). If resistance is less than 100,000 ohms, repair short circuit and repeat QUICK TEST.

5) Check IMRC Circuit For Short To Power  Turn ignition off. Measure resistance between test pin No. 32 and test pins No. 37 and 57 atbreakout box. If resistance is 100,000 ohms or more, replace PCM and repeat QUICK TEST. If resistance is less than 100,000 ohms, repair short circuit and repeat QUICK TEST. If fault is still present, replace PCM. Repeat QUICK TEST.

6) Check IMRC Valves  Turn ignition off. Disconnect vacuum lines from both IMRC valves. Use vacuum pump to apply 10 in. Hg vacuum to each IMRC valve. If both valves hold vacuum, go to step 7). If valve(s) do not hold vacuum, replace as necessary and repeat QUICK TEST.

7) Check Operation Of IMRC Valves  Apply 10 in. Hg to each air valve. If both valves and mechanical linkage move in response to applied vacuum, go to step 8). If valves and/or linkage do not move, repair as necessary and repeat QUICK TEST.

8) Check Vacuum IMRC Valves  Check vacuum lines from IMRC valves to solenoids. Inspect vacuum lines for damage and blockage. If vacuum lines are damaged or blocked, repair as necessary. If vacuum lines are okay, go to step 9).

9) Enter OUTPUT STATE CHECK  Use only VOM or DVOM for this step. DO NOT use scan tester. Turn ignition off. Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at Data Link Connector (DLC). Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at DLC. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate PCM has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases to 10.5 volts or more, remain in OUTPUT STATE CHECK and go to step 10). If voltage does not increase to 10.5 volts, depress throttle to WOT and release. If STO voltage does not go high, go to CIRCUIT TEST QC.

10) Check IMRC Solenoid Electrical Operation  Turn ignition off. Disconnect IMRC solenoid wiring harness connector. Connect DVOM positive lead to connector VPWR terminal. Connect negative lead to connector IMRC terminal. Observe DVOM while cycling throttle open and closed. If DVOM does not cycle 0.5 volt, return to step 1). If DVOM does cycle 0.5 volt, go to next step.

11) Check IMRC Solenoid Vacuum  Disconnect IMRC solenoid vacuum hose and wiring harness connector. Turn ignition on. Use vacuum pump to apply 16 in. Hg vacuum to each IMRC valve. If vacuum is not held for 20 seconds, replace solenoid and repeat QUICK TEST. If vacuum is held, go to next step.

12) Check IMRC Solenoid Mechanical Operation  Remain in OUTPUT STATE CHECK. Use vacuum pump to apply 16 in. Hg vacuum to each IMRC valve. Depress and release throttle. If vacuum is not released, replace solenoid and repeat QUICK TEST. If vacuum is released, go to next step.

13)  Disconnect IMRC solenoid vacuum hose. Start engine. Check vacuum at disconnected hose. If vacuum is present at hose, system is okay. If vacuum is not present, check supply hose to IMRC solenoid. Repair as necessary, and repeat QUICK TEST.

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