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Circuit Test D1

NOTE: Perform this test when Service Code 34 is displayed during QUICK TESTS or when directed here by other test procedures. Code 34 may be result of high volume exhaust vent system reducing backpressure. If this is suspected, perform test in well-ventilated area without exhaust vent connected.
Fig 1: EGR On/Off Circuit
G108586

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: air or vacuum leaks, EGR flow restrictions or EGR valve.

  1. Code 34: Enter Output State Check. KOER Code 34 indicates that with engine RPM above idle and stable, a specified RPM drop did not occur when EGR was cycled. Possible causes for this fault are:
    • Faulty EGR On/Off control solenoid
    • Faulty EGR solenoid
    • Faulty EGR vent solenoid
    • Faulty EVP sensor
    • Faulty wiring harness
    • Faulty ECA
    • Manifold vacuum line blocked or leaking

    Use only VOM/DVOM, not diagnostic tester, for this step. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect negative DVOM lead to STO at SELF-TEST connector and positive lead to positive battery terminal. Jumper STI to SIGNAL RETURN at SELF-TEST connector. Rerun KOEO SELF-TEST until end of CONTINUOUS SELF-TEST code display (DVOM will read zero volts). Depress and release throttle and observe DVOM reading. If DVOM reading changes to a higher voltage, stay in OUTPUT STATE CHECK and go to next step. If DVOM did not show high voltage, depress throttle to WOT and release. If STO voltage does not go high, go to CIRCUIT TEST D16 , step 1). Leave test equipment hooked up.

  2. Checking Solenoid Electrical Operation. Set DVOM on 20 volt scale. Connect DVOM positive lead to VPWR circuit at EGR solenoid and negative lead to EGR output circuit. Depress and release throttle several times to cycle EGR solenoid output on and off. If output does not cycle on and off, remove STI jumper wire and go to step 5). If output cycles on and off, go to next step.
  3. Checking Solenoid For Vacuum Cycling. Connect vacuum pump to solenoid vacuum supply port and vacuum gauge to output port of solenoid. Apply minimum vacuum of 6 in. Hg. Depress and release throttle several times to cycle EGR solenoid output while maintaining vacuum at supply port. Note gauge reading. If vacuum output does not cycle, replace EGR solenoid and repeat QUICK TEST. If vacuum output cycles, go to next step.
  4. Checking Manifold Vacuum Lines. With vacuum lines disconnected at EGR solenoid, start engine. If vacuum is present, EEC system is not cause of problem. Check exhaust gas recirculation system. If vacuum is not present, correct vacuum source blockage or leak and repeat QUICK TEST.
  5. Measuring Solenoid Resistance. Turn key off and wait 10 seconds. Disconnect EGR solenoid. Set DVOM on 200-ohm scale and measure solenoid resistance. If reading is less than 65 ohms or more than 110 ohms, replace EGR solenoid and repeat QUICK TEST. If reading is between 65 and 110 ohms, go to next step.
  6. Checking VPWR Circuit. With KOEO, set DVOM on 20-volt scale. Measure voltage between VPWR circuit at EGR solenoid harness connector and battery ground. If reading is less than 10.5 volts, repair open in harness and repeat QUICK TEST. If reading is 10.5 volts or more, go to next step.
  7. Checking Continuity of EGR Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 35 at the breakout box and EGR circuit at harness connector. If reading is 5 ohms or more, repair open circuit and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
  8. Checking Circuit For Short to Ground. Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. Disconnect EGR solenoid. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 35 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, repair short to ground and repeat QUICK TEST. If all readings are 10K ohms or more, go to next step.
  9. Checking For Short to Power Circuit. Turn key off and wait 10 seconds. Leave breakout box installed. Disconnect ECA and EGR solenoid. With DVOM on 200K-ohm scale, measure resistance between test pin No. 35 and test pins No. 37 and 57. If any reading is less than 10K ohms, repair short to power and repeat QUICK TEST. If code is still repeated, replace ECA. If all readings are 10K ohms or more, replace ECA and repeat QUICK TEST.
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