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Circuit Test K

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: Check for air leaks between vane airflow meter and throttle body. Check for vacuum leaks. Check engine sealing at PCV, CANP, valve cover(s), and at dipstick seal.

  1. Code 26 Displayed. Code 26 indicates VAF sensor input to ECA is out of closed (engine not running) or idle limits (engine off 0.15 to 0.50 volts; engine idling 1.5 to 2.7 volts). There have been no shorts or opens in VAF circuit; either code 56 (signal always high) or code 66 (signal always low) would have been displayed. Turn key off and wait 10 seconds. Remove air filter and check for contamination (oil or foreign matter). If code 26 appears in KEY ON/ENGINE OFF SELF-TEST, replace airflow meter. Install air cleaner and repeat QUICK TEST  . If code 26 is not displayed, go to next step.
  2. With key off and air filter installed, check for air leaks allowing unmetered air into system between airflow meter and throttle body. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA to box. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Place new, unsharpened wooden pencil through air inlet opening of airflow meter. Measure voltage between test pins No. 43 and 46. If reading is between 2.8 and 3.7 volts, airflow meter is okay. Code 26 has been caused by incorrect engine speed or vacuum leak. Repair problem, remove breakout box, then repeat QUICK TEST  . If reading is not between 2.8 and 3.7 volts, replace ECA, remove breakout box, and then repeat QUICK TEST  .
  3. Code 56 Displayed. Turn key off and wait 10 seconds. Disconnect harness from airflow meter. Inspect for and repair any damaged wiring. Perform KEY ON/ENGINE OFF SELF-TEST. If code 66 is not displayed, go to step 5). If code 66 is displayed, go to next step. Disconnecting airflow meter also disconnects VAT sensor, code 54 should be displayed. Ignore all codes except VAF codes at this time.
    Fig 1: VAF Sensor Check
    G48109
  4. Turn key off and wait 10 seconds. Leave harness disconnected from airflow meter. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage at harness connector between VREF and signal return. If reading is between 4.0 and 6.0 volts, replace airflow meter. Connect harness and repeat QUICK TEST  . If reading is less than 4.0 or more than 6.0 volts, go to CIRCUIT TEST C  , step 1).
  5. Turn key off and wait 10 seconds. Leave airflow meter disconnected. Disconnect 60-pin connector from ECA. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pin No. 43 and test pins No. 26 and 57. If either reading is less than 10,000 ohms, repair short in wiring. Remove breakout box. Connect ECA and airflow meter and then repeat QUICK TEST  . If both readings are 10,000 ohms or higher, replace ECA. Remove breakout box. Connect ECA and airflow meter. Repeat QUICK TEST  .
  6. Code 66 Displayed. Turn key off and wait 10 seconds. Disconnect harness from airflow meter. Install jumper wire between VREF and VAF signal at connector. Perform KEY ON/ENGINE OFF SELF-TEST. Ignore all codes except VAF codes at this time. If no codes are displayed, immediately remove jumper wire and go directly to step 9). If code 56 is displayed, replace airflow meter. Remove jumper wire, connect airflow meter, and then repeat QUICK TEST  . If code 56 is not displayed, remove jumper wire and go to next step.
  7. Turn key off and wait 10 seconds. Leave airflow meter disconnected. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between VREF and signal return at airflow meter harness connector. If reading is less than 4.0 volts or more than 6.0 volts, go to CIRCUIT TEST C  , step 1). If reading is between 4.0 and 6.0 volts, go to next step.
  8. With key off and airflow meter 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 VAF signal at airflow connector and test pin No. 43. If reading is 5 ohms or more, repair open circuit. Remove breakout box, connect ECA and airflow meter. Repeat QUICK TEST  . If reading is less than 5 ohms, go to next step.
  9. Turn key off and wait 10 seconds. Leave ECA and airflow meter disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between VAF signal and signal return at harness connector. Also measure resistance between VAF signal and negative battery terminal. If either reading is less than 10,000 ohms, repair shorts. Connect airflow meter and repeat QUICK TEST  . If both readings are 10,000 ohms or more, replace ECA. Remove breakout box, and connect ECA and airflow meter. Repeat QUICK TEST  .
    NOTE: A sharp snap of the throttle may not be sufficient to pass step 10). Be sure to move throttle to WOT. Use DYNAMIC RESPONSE CHECK as specified. For additional information see QUICK TEST DIAGNOSTIC AIDS  , DYNAMIC RESPONSE CHECK in front of this article.
  10. Code 76 Displayed. 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 to box. Set DVOM on 20 volt scale and connect to test pins No. 43 and 46. Perform ENGINE RUNNING SELF-TEST while observing DVOM. As soon as DYNAMIC RESPONSE CHECK signal is displayed, perform WOT. Reading on DVOM should increase by more than 2.0 volts from reading before WOT. Observe service codes at end of test. If reading increased by more than 2.0 volts and code 76 is still displayed, replace ECA. Remove breakout box and repeat QUICK TEST  . If reading did not increase more than 2.0 volts, check air cleaner duct for blockage. If duct is clear, replace airflow meter. If reading increased by more than 2.0 volts and code 76 is not displayed, airflow meter is okay. Service other codes as necessary.
  11. Continuous Code 56 or 66 Displayed. Using CONTINUOUS MONITOR (WIGGLE) TEST  , observe VOM or STAR tester LED for indication of fault while lightly tapping VAF sensor and wiggling connector. If a fault is indicated, disconnect connector. Inspect connector and terminals for damage. If connector and terminals are okay, replace VAF sensor and repeat QUICK TEST  . If no fault is indicated, go to next step.
  12. While in CONTINUOUS MONITOR (WIGGLE) TEST  , shake, bend and wiggle small sections of EEC-IV harness from VAF sensor connector to firewall and from firewall to ECA. If fault is indicated, isolate and repair damaged wiring. Repeat QUICK TEST  . If no fault is indicated, go to next step.
  13. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are damaged, repair as necessary and repeat QUICK TEST  . If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous code 56 or 66 testing is complete.
Fig 2: VAF Sensor Circuit
G42682
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