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Test I - Airflow Sensor

  1. Code 26. Code 26 indicates airflow sensor input to ECA is out of closed limits (Engine Off) or idle limits (Engine Off .15-.50 volts; Engine at Idle 1.5-2.7 volts). There are no shorts or opens in circuit or code 56 or 66 would have been generated. Turn ignition off and wait 10 seconds. Check for air or vacuum leaks. Remove air filter and check for contamination. If code 26 appears in Key On-Engine Off Self-Test, replace airflow meter and repeat Quick Test. If no code 26, go to next step.
  2. Turn ignition off and reinstall air filter. Disconnect 60-pin connector at ECA and inspect. Install breakout box and connect ECA to box. Place DVOM on 20 volt scale. Turn ignition on. Place an unsharpened wooden pencil through air inlet opening of airflow meter. Pencil must pass completely through opening. Measure voltage between breakout box pins 43 and 46. If 2.8-3.7 volts, airflow meter is capable of outputting signals. Code 26 has been caused by incorrect engine speed, or vacuum leak. Repair and repeat Quick Test. If voltage not 2.8-3.7, replace ECA and repeat Quick Test.
  3. Turn ignition off and wait 10 seconds. Disconnect harness from airflow meter. Set DVOM on 20 volt scale. Measure voltage of airflow meter harness between signal return circuit and battery positive post. If reading is 10 volts or more, go to next step. If less than 10 volts, go to step 6).
  4. With airflow meter disconnected, turn ignition on. Measure voltage of airflow meter harness between airflow signal circuit to signal return circuit. If less than 4 volts, go to next step. If 4 volts or more, go to step 7).
  5. With airflow meter disconnected, perform Key On-Engine Off Self-Test. If code 66 appears, replace airflow meter and repeat Quick Test. If no code 66, replace ECA and repeat Quick Test. Disregard all other codes.
  6. With airflow meter disconnected, turn ignition off. Disconnect 60-pin connector at ECA and inspect. Install breakout box, ECA disconnected. With DVOM on 200 ohm scale, measure resistance of airflow meter harness between signal return circuit and box pin 46. If less than 5 ohms, replace ECA and repeat Quick Test. If 5 ohms or more, repair open in circuit and repeat Quick Test.
  7. Turn ignition off and wait 10 seconds. With same connections as in step 6), set DVOM on 200,000 ohm scale. Measure resistance between box pin 43 and pins 26 and 57. If either less than 10,000 ohms, repair short in circuit and repeat Quick Test. If both 10,000 ohms or more, replace ECA and repeat Quick Test.
  8. Code 66. Turn ignition off and wait 10 seconds. Disconnect harness at airflow meter and inspect. Turn ignition on. With DVOM on 20 volt scale, measure voltage of airflow meter harness between voltage reference circuit and signal return circuit. If 4-6 volts, go to next step. If less than 4 volts, go to step 12). If more than 6 volts, go to Test C.
  9. Turn ignition off and wait 10 seconds. With airflow meter disconnected, disconnect 60-pin connector at ECA and inspect. Leave ECA disconnected. Measure resistance of airflow meter harness between airflow signal circuit and signal return circuit. If less than 10,000 ohms, repair short in circuit and repeat Quick Test. If 10,000 ohms or more, reconnect ECA and go to next step.
  10. Turn ignition off and wait 10 seconds. With ECA and airflow meter disconnected, install jumper wire in airflow meter harness between voltage reference circuit and airflow signal circuit. Perform Key On-Engine Off Self-Test. If code 56 appears, replace airflow meter and repeat Quick Test. If no code 56, remove jumper wire and go to next step.
  11. Ignition off, airflow meter disconnected. Disconnect 60-pin connector at ECA and inspect. Install breakout box and leave ECA disconnected. With DVOM on 200 ohm scale, measure resistance of airflow meter harness between airflow signal circuit and box pin 43. If less than 5 ohms, replace ECA and repeat Quick Test. If 5 ohms or more, repair short in circuit and repeat Quick Test.
  12. Turn ignition off and wait 10 seconds. Breakout box connected, ECA and airflow meter disconnected. With DVOM on 200 ohm scale, measure resistance of airflow meter harness between voltage reference signal circuit and box pin 26. If less than 5 ohms, replace ECA and repeat Quick Test. If 5 ohms or more, repair open in circuit and repeat Quick Test.
  13. Code 76. Turn ignition off and wait 10 seconds. Disconnect 60-pin connector at ECA and inspect. Install breakout box and reconnect ECA. Place DVOM on 20 volt scale and connect between box pins 43 and 46. Perform Engine Running Self-Test while watching DVOM. After Dynamic Response Code is indicated, perform WOT. DVOM should increase more than 2 volts. Check code at end of test. If DVOM increased 2 volts, but code 76 still present, replace ECA and repeat Quick Test. If DVOM did not increase more than 2 volts, check air cleaner for obstructions. If okay, replace airflow meter and repeat Quick Test. If DVOM increased more than 2 volts and code 76 not present, airflow meter okay. Service other codes.
  14. Continuous Monitor Codes 56 and 66. Using Continuous Monitor mode, observe volt/ohmmeter for fault indication while doing the following: Lightly tap on airflow sensor and then wiggle sensor harness. If fault is indicated, disconnect and inspect harness and connector. If okay, replace airflow sensor and repeat Quick Test. If no fault indicated, go to next step.
  15. Observe volt/ohmmeter while doing the following: Beginning at airflow sensor, wiggle, shake or bend small sections of harness while working way to dash panel. Then repeating process from panel to ECA. If fault is indicated, isolate and repair problem and repeat Quick Test. If no fault indicated, go to next step.
  16. Turn ignition off and wait 10 seconds. Disconnect 60-pin connector at ECA and check for damage at ECA pins and connector terminals. Repair as required and repeat Quick Test. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Code 56 and 66 testing is complete.
Fig 1: Airflow Sensor Test Circuits
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