Circuit Test B4

Fig 1: EVP, EGRC & EGRV Solenoid Circuits

To prevent replacement of good components, be aware that the following non-EEC related area may be at fault: damaged EGR valve.

1. KOER Code 31. Code 31 indicates that during the KOER SELF-TEST the EVP sensor signal was out of range with the EGR valve in the closed position. Possible causes for this code are a faulty EGRC/EGRV solenoids or a clogged EGRV filter. Turn key off and wait 10 seconds. Disconnect and plug vacuum line at EGR valve. Perform KOER SELF-TEST. If Code 31 is not displayed, reconnect vacuum and go to step 8). If Code 31 is displayed, go to next step. Ignore all other service codes at this time.
2. KOEO Code 31: Checking EVP Resistance With Vacuum Applied. Code 31 displayed during the KOEO SELF-TEST indicates that the EVP sensor signal was out of range with the EGR valve in the closed position. Possible causes for this code are, an open or shorted circuit, faulty EGR valve, faulty EVP sensor, or a faulty ECA. Turn key off and wait 10 seconds. Leave EGR vacuum line disconnected and plugged. Disconnect EVP sensor harness. Set DVOM on 200K-ohm scale and connect vacuum pump to EGR valve. Measure resistance between EVP SIG and VREF at EVP connector while vacuum is slowly increased to 10 in. Hg. If reading is less than 100 ohms or more than 5500 ohms, replace EVP sensor. Connect vacuum line and harness. Repeat QUICK TEST. If reading does not decrease or valve does not hold vacuum, go to step 11). If reading gradually decreases from a maximum of 5500 ohms to a minimum of 100 ohms, go to next step.
3. Checking EVP Signal for Shorts to VREF and SIG RTN. With KOEO, disconnect harness from EVP sensor. Set DVOM on 20-volt scale. Measure voltage between VREF and SIG RTN at EVP connector. If reading is less than 4 volts or more than 6 volts, go to CIRCUIT TEST A3 , step 1). If reading is between 4 and 6 volts, go to next step.
4. Checking EVP Signal Continuity. Turn key off and wait 10 seconds. Disconnect harness at EVP sensor and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 27 and EVP SIG at EVP connector. If reading is 5 ohms or more, repair open in circuit. Remove breakout box, connect ECA and EVP sensor, and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
5. Checking EVP Signal Circuit for Shorts. Turn key off and disconnect harness at EVP sensor. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 27 and test pins No. 26, 40, 46, and 60. If any reading is less than 10K ohms, repair short circuit. Remove breakout box, connect ECA and EVP sensor. Repeat QUICK TEST. If all readings are 10K ohms or more, go to next step.
6. EVP Sensor and EGR Valve Substitution Test. Turn key off and wait 10 seconds. Connect known good EVP sensor and EGR valve assembly to harness and vacuum lines. Connect ECA to breakout box. Perform KOEO SELF-TEST. If code 31 is displayed, replace ECA. Connect original EVP sensor and EGR valve assembly. Repeat QUICK TEST. If Code 31 is not displayed, go to next step.
7. Testing EVP Sensor. Turn key off and wait 10 seconds. Ensure breakout box is installed and ECA is connected. Install original EVP sensor to known good EGR valve. Connect EVP sensor and perform KOEO SELF-TEST. If Code 31 is displayed, replace EVP sensor and repeat QUICK TEST. If Code 31 is not displayed, service EGR system.
8. Codes 32, 33, or 34 Displayed. Codes 32, 33 or 34 indicate that the EGR valve did not open when instructed to by the ECA. Code 34 indicates the valve would not open. Code 32 indicates the valve is stuck open. Code 33 indicates the valve would not close correctly. Possible causes for these faults are as follows:
   • Faulty vacuum lines.
   • Clogged EGRV filter.
   • Faulty EVP sensor.
   • Faulty EGR valve.
   • Faulty EGRC/EGRV solenoid.
   • Faulty ECA.

   With key off, disconnect vacuum line at the EGR valve. Connect a vacuum gauge to the vacuum line, leaving the EGR valve disconnected. Observe vacuum gauge while running KOER SELF-TEST. Disregard all other codes produced during this test. If vacuum reading increased from less than one in. Hg to greater than 5 in. Hg and, within 10 seconds, returned to less than one in. Hg go to step 10). If vacuum did not increase, go to next step. If vacuum increased but did not return to less than one in. Hg, check EGRV filter for obstructions, replace filter or solenoid as necessary. Reconnect all vacuum lines and rerun QUICK TEST.

9. Checking Vacuum Supply to EGRC/EGRV Solenoids. With key off, disconnect vacuum source to EGRC/EGRV solenoids. Install a vacuum gauge at the source vacuum line. Start engine and check vacuum. If vacuum is greater than 10 in. Hg, check vacuum line from EGRC/EGRV solenoids to EGR valve for blockage, leaks or damage, replace as necessary. If supply line is okay, replace solenoid assembly and rerun QUICK TEST. If vacuum was below specification, check vacuum source and repair as necessary.
10. Checking EVP Resistance. With key off, disconnect EVP sensor harness. Inspect for and repair any damaged wiring. Set DVOM on 200K-ohm scale. Disconnect vacuum line at EGR valve and connect vacuum pump to valve. Measure resistance of EVP sensor between EVP signal and VREF terminals while increasing vacuum to 10 in. Hg If reading slowly decreases from maximum of 5500 ohms to minimum of 100 ohms, replace ECA. Connect EVP sensor and EGR vacuum line. Repeat QUICK TEST. If reading does not slowly decrease, go to next step.
11. Manual Test of EVP Sensor. With key off, disconnect EVP sensor harness. Remove EVP sensor and vacuum line from EGR valve. Measure resistance of EVP SIG and VREF at the connector while sensor shaft is slowly pushed in and slowly released. If reading increases and decreases smoothly in range of 100-5500 ohms, service or replace EGR valve assembly. Connect EVP sensor and EGR vacuum line. Repeat QUICK TEST. If either reading changes abruptly during range of 100-5500 ohms, replace EVP sensor. Reconnect harness and EGR vacuum line. Repeat QUICK TEST.
    NOTE: It is normal for EVP sensor total resistance to drop to less than 100 ohms when disconnected from EGR valve. A defective sensor will change resistance suddenly between 5500 and 100 ohms.
12. Code 83 or 84 Displayed: Checking EGRV/EGRC Solenoid Resistance. A Code 83 indicates an EGRC circuit failure. A Code 84 indicates an EGRV circuit failure. Possible causes for these faults are an open or shorted circuit, a faulty EGRC/EGRV solenoid or a faulty ECA. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect EGRC and EGRV solenoids from harness. Inspect for and repair any damaged wiring. Measure resistance of both solenoids. If either reading is less than 30 ohms or more than 70 ohms, replace EGRC/EGRV solenoid assembly. Repeat QUICK TEST. If both readings are between 30 and 70 ohms, reconnect solenoids and go to next step.
13. Checking VPWR at EGRC/EGRV Solenoids. Disconnect EGRC and EGRV solenoids from harness. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between battery negative terminal and VPWR circuit for both solenoids. If either reading is less than 10.5 volts, repair open circuit and repeat QUICK TEST. If both readings are 10.5 volts or more, go to next step.
14. Continuity Check. Turn key off and wait 10 seconds. Leave EGRC and EGRV solenoids disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 33 and EGRV signal at EGRV solenoid connector. Measure resistance between test pin No. 52 and EGRC signal at EGRC solenoid connector. If either reading is 5 ohms or more, repair open circuit. Remove breakout box, connect ECA solenoids, and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.
15. Checking For Shorts To Ground. Turn key off and wait 10 seconds. Set DVOM on 200K-ohm scale. Install breakout box, leaving ECA disconnected. Disconnect EGRC and EGRV solenoids. Measure resistance between test pin No. 33 and test pins No. 40, 46, and 60. Measure resistance between test pin No. 52 and test pins No. 40, 46, and 60. If readings are less than 10K ohms, repair short to ground. Repeat QUICK TEST. If readings are 10K ohms or more, go to next step.
16. Checking For Shorts To Power. With key off, disconnect EGRC and EGRV solenoids from harness. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 33 and test pins No. 37 and 57. Measure resistance between test pin No. 52 and test pins No. 37 and 57. If any reading is less than 10K ohms, repair short in circuit. Remove breakout box and connect ECA. Repeat QUICK TEST. If all resistances are greater than 10K ohms, replace ECA. Remove breakout box and connect ECA. Repeat QUICK TEST.
17. Code 35: RPM To Low For EGR Test. This code indicates that engine RPM is too low for correct EGR testing. Possible causes for this fault are a faulty ISC system or a faulty ECA. If Code 12 is also displayed go to CIRCUIT TEST D5 , step 1). If Code 12 is not displayed with Code 35, go to next step.
18. Retest at 1500 RPM. Turn key off and wait 10 seconds. Install tachometer. Perform KOER SELF-TEST at 1500 RPM. Ignore all other codes at this time. Record KOER service codes. If code 35 is displayed, replace ECA. Clear codes and repeat QUICK TEST. If code 35 is not displayed, clear codes and repeat QUICK TEST and repair codes as necessary.
19. Continuous Code 31 Displayed. Continuous Code 31 indicates that sometime during vehicle operation the EVP signal was out of the Self-Test range. Possible causes for this fault are an open or shorted circuit or a faulty EVP sensor. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while doing the following: connect vacuum pump to EGR valve. Very slowly apply 6 in. Hg vacuum to EGR valve. Bleed vacuum slowly and lightly tap on EVP sensor. Wiggle EVP sensor connector. If fault is indicated, go to next step. If no fault is indicated, go to step 21).
20. EVP Signal Voltage During Operation. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Stay in KOEO CONTINUOUS MONITOR (WIGGLE) TEST. Connect DVOM between test pins No. 27 and 46. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Repeat step 19) while watching voltage. If fault occurs below 4.25 volts, disconnect EVP sensor from harness. Inspect for and repair any damaged wiring. If wiring is okay, replace EVP sensor. Clear codes and repeat QUICK TEST. If fault does not occur below 4.25 volts, EGR valve overshoot may have caused Continuous Memory Code 31. Sensor test is complete. Go to next step for harness test.
21. Checking Harness. While in KOEO CONTINUOUS MONITOR (WIGGLE) TEST, bend, shake, and wiggle small sections of EEC-IV harness from sensor to firewall and from firewall to ECA. If fault is indicated, isolate fault and repair as necessary. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.
22. Checking ECA and Harness Connectors. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and terminals for obvious damage. If connector and terminals are damaged, repair as necessary and repeat QUICK TEST. If connector and terminals are okay, fault cannot be duplicated at this time. Continuous Code 31 testing is complete.