Diagnostic Aids

Perform this test when instructed by QUICK TEST or if directed by other test procedures.

To prevent replacement of good components, be aware the following non-EEC related areas may be cause of problem:

• Damaged EGR valve.
• Damaged EGR transducer.
• Stuck throttle plate.
• Exhaust system restriction.
• Damaged canister, reservoir and/or vacuum hoses.

This CIRCUIT TEST is intended to diagnose the following:

• EGRT sensor.
• EGRT and SIG RTN wiring harness circuits.
• Powertrain Control Module (PCM).
  Fig 1: EGR Temperature (EGRT) Sensor Circuits/Connector Terminals

  

1. 1) Continuous Memory Code 327: Verification
   
   Code 327 indicates that at least once within previous 40 warm-up cycles, EGRT sensor signal was less than self-test minimum. Possible causes for this fault are:
   • Faulty EGRT sensor.
   • Open or grounded wiring harness.
   • Faulty PCM.

   Turn ignition off. Clear codes from PCM memory. Start engine, and let it run for at least 2 minutes. Repeat KOEO SELF-TEST  . If Code 327 is not displayed, go to step 90). If Code 327 is displayed, go to next step.

2. 2) Induce Opposite Code
   
   Clear codes from PCM memory. Disconnect EGRT sensor. Start engine, and let it run for at least 2 minutes. Repeat KOEO SELF-TEST  . If Code 337 is not displayed, go to next step. If Code 337 is displayed, replace EGRT sensor. Clear continuous memory, and repeat QUICK TEST  .
3. 3) Check EGRT Circuit For Short To Ground
   
   Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect EGRT sensor wiring harness connector. Measure resistance between test pin No. 43 and pins No. 40, 46 and 60 at breakout box. If all readings are 10,000 ohms or more, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST  . If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST  .
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 5). No test procedures have been omitted.
4. 5) Continuous Memory Code 337: Verification
   
   Code 337 indicates that at least once within previous 40 warm-up cycles, EGRT sensor signal was more than self-test maximum. Possible causes for this fault are:
   • Faulty EGRT sensor.
   • Open wiring harness circuit.
   • Faulty PCM.

   Clear codes from PCM memory. Start engine, and let it run for at least 2 minutes. Repeat KOEO SELF-TEST  . If Code 337 is not displayed, go to step 90). If Code 337 is displayed, go to next step.

5. 6) Check EGRT Circuit For Short To Power
   
   Turn ignition off. Disconnect EGRT sensor. Turn ignition on. Measure voltage between EGRT terminal at EGRT sensor wiring harness connector and negative battery terminal. If voltage is 1.0 volt or more, repair short and repeat QUICK TEST  . If voltage is less than 1.0 volt, go to next step.
6. 7) Induce Opposite Code
   
   Clear codes from PCM memory. Connect jumper wire between EGRT terminal and SIG RTN terminal at EGRT sensor wiring harness connector. Start engine, and let it run for at least 2 minutes. Repeat KOEO SELF-TEST  . If Code 327 is displayed, replace EGRT sensor. Clear continuous memory, and repeat QUICK TEST  . If Code 327 is not displayed, go to next step.
7. 8) Check Continuity Of Circuits
   
   Turn ignition off. Disconnect PCM 60-pin connector. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM and EGRT sensor disconnected. Measure resistance between EGRT terminal at EGRT wiring harness connector and test pin No. 43 at breakout box. Also, measure resistance between SIG RTN terminal at EGRT wiring harness connector and test pin No. 46 at breakout box. If either reading is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST  . If both readings are less than 5 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST  .
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 8) to step 10). No test procedures have been omitted.
8. 10) Continuous Memory Code 326
   
   Code 326 indicates that within previous 40 warm-up cycles, PCM detected EGR flow at idle. Possible causes for this fault are:
   • EGR valve stuck open.
   • Faulty EGRT sensor.
   • Open or shorted wiring harness circuit.

   Clear codes from PCM memory. Start engine, and let it run for at least 2 minutes. If engine idles rough or stalls, clean or replace EGR valve. If engine does not stall or idle rough, go to next step.

9. 11) Verify Condition
   
   Repeat KOEO SELF-TEST  . If Continuous Memory Code 326 is not present, go to step 90). If Continuous Memory Code 326 is present, go to next step.
10. 12) Check Continuity Of Harness Circuits
    
    Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect EGRT sensor connector. Measure resistance between EGRT terminal at EGRT wiring harness connector and test pin No. 43 at breakout box. Also, measure resistance between SIG RTN terminal at EGRT wiring harness connector and test pin No. 46 at breakout box. If either resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST  . If either resistance is less than 5 ohms, replace EGRT sensor. Remove breakout box, reconnect all components, and repeat QUICK TEST  .
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 20). No test procedures have been omitted.
11. 20) Continuous Memory Code 332
    
    Code 332 indicates that within previous 80 warm-up cycles, PCM did not detect EGR flow at part throttle. Possible causes for this fault are:
    • Damaged or plugged vacuum line.
    • EGR valve stuck closed.
    • Damaged EGR pressure transducer.
    • Damaged or plugged exhaust tube.
    • Faulty EGRT sensor.
    • Open or shorted wiring harness circuit.

    Turn ignition off. Disconnect vacuum hose at EGR valve. Connect vacuum pump to EGR valve. Apply 10 in. Hg to EGR valve. If vacuum is not held, repair or replace EGR valve. If vacuum is held, go to next step.

12. 21)
    
    Release vacuum from EGR valve. Clear codes from PCM memory. Start engine. Apply 10 in. Hg to EGR valve, and hold 2 minutes. If engine idles rough or stalls, go to next step. If engine does not idle rough or stall, clean or replace EGR valve.
13. 22)
    
    Repeat KOEO SELF-TEST  . If Continuous Memory Code 326 is present, clean or repair EGR system as necessary. See EMISSION SYSTEMS & SUB-SYSTEMS in the SYSTEM/COMPONENT TESTS article. If Continuous Memory Code 326 is not present, replace EGRT sensor and repeat QUICK TEST  .
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 90). No test procedures have been omitted.
14. 90) Check EEC-IV Wiring Harness
    
    Enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST)  under QUICK TEST. Bend, wiggle and shake small sections of EEC-IV harness from TP sensor wiring harness connector to firewall and from firewall to PCM while observing analog voltmeter or scan tester. If fault is indicated, isolate fault in wiring and repair as necessary. Clear codes, and repeat QUICK TEST  . If no fault is indicated, go to next step.
15. 91) Check PCM & Harness Connectors
    
    Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Clear codes from PCM memory, and repeat QUICK TEST  . If connectors and terminals are okay, fault cannot be duplicated at this time. Testing is complete.