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Test M - Air Charge Temperature (Act) Sensor

NOTE: Ambient air temperature must be greater than 50°F (10°C) for this test.
  1. Code 24. For vehicles with ACT sensor mounted in intake manifold, go to next step. On all other models, if sensor is properly mounted in air cleaner, go to next step. If sensor is not properly mounted, install properly and repeat QUICK TEST  .
  2. Turn ignition off and wait 10 seconds. Disconnect harness at ACT and check for damaged pins or corrosion. Repair as required. Turn ignition on (engine off). With DVOM on 20 volt scale, measure voltage from ACT signal circuit and signal return circuit of sensor harness. If reading is 4-6 volts, go to step  5 . If reading is less than 4 volts, go to step  3 . If reading is greater than 6 volts, go to TEST C  .
  3. Turn ignition off and wait 10 seconds. Harness disconnected at ACT sensor. Disconnect 60-pin connector at ECA. Connect breakout box and leave ECA disconnected. With DVOM on 200 ohm scale, measure resistance from box pin 26 to ACT signal circuit of sensor connector. Then measure resistance from box pin 46 to signal return circuit of sensor connector. If both readings less than 5 ohms, go to next step. If either reading 5 ohms or more, repair open circuit and repeat QUICK TEST  .
  4. Turn ignition off. Breakout box connected and ECA and ACT disconnected. With DVOM on 200,000 ohm scale, measure resistance from box pin 25 to pins 40, 46 and 60 in turn. If any reading less than 10,000 ohms, repair short circuits and repeat QUICK TEST  . If all readings 10,000 ohms or more, go to next step.
  5. Remove breakout box and reconnect all connectors. Warm engine to normal operating temperature. Turn ignition off and wait 10 seconds. Disconnect harness at ACT sensor. With DVOM on 200,000 ohm scale, measure resistance of sensor. If 1100-58,000 ohms (at about 50°F/10°C), go to next step. If less than 1100 ohms or more than 58,000 ohms, check heat stove duct valve operation. If duct valve operation is okay, replace sensor and repeat QUICK TEST  .
  6. Turn ignition off. With harness disconnected at ACT sensor, start and run engine for 2 minutes. With DVOM on 200,000 ohm scale, measure resistance of sensor while engine is running. If reading is 2400-29,000 ohms, replace ECA and repeat QUICK TEST  . If reading is less than 2400 ohms or greater than 29,000 ohms, check heat stove duct valve operation. If duct valve operation is okay, replace sensor and repeat QUICK TEST  .
  7. Code 54. Turn ignition off and wait 10 seconds. Disconnect harness at ACT sensor and inspect for damage. Repair as required. Insert jumper wire between ACT signal circuit and signal return circuit of harness. Perform KEY ON-ENGINE OFF (KOEO) SELF-TEST  . If code 64 present, replace sensor and repeat QUICK TEST  . If no code 64, remove jumper wire and go to next step.
  8. Turn ignition off and wait 10 seconds. ACT connector disconnected. Disconnect 60-pin connector at ECA and inspect for damage. Repair as required. Connect breakout box and leave ECA disconnected. With DVOM on 200 ohm scale, measure resistance between box pin 25 and ACT signal circuit of ACT harness. Then measure between box pin 46 and signal return circuit of ACT harness. If both readings are less than 5 ohms, replace ECA and repeat QUICK TEST  . If either reading is 5 ohms or more, repair open circuit and repeat QUICK TEST  .
  9. Code 64. Turn ignition off and wait 10 seconds. Disconnect harness at ACT sensor and inspect. Repair as required. Perform KEY ON-ENGINE OFF (KOEO) SELF-TEST  . If code 54, replace ACT sensor and repeat QUICK TEST  . If no code 54, go to next step.
  10. Turn ignition off and wait 10 seconds. Harness disconnected at ACT sensor. Disconnect 60-pin connector at ECA and inspect. Repair as required. Connect breakout box and leave ECA disconnected. With DVOM on 200,000 ohm scale, measure resistance from box pin 25 to pins 40, 46 and 60 in turn. If any reading less than 10,000 ohms, repair short circuit and repeat QUICK TEST  . If all readings 10,000 ohms or more, replace ECA and repeat QUICK TEST  .
  11. Continuous codes 54 and 64. Breakout box disconnected and ECA and ACT connected. Enter Continuous Monitor mode and observe volt/ohmmeter for fault indication while doing the following: Lightly tap on ACT sensor to simulate road shock. Wiggle sensor connector. If fault is indicated, disconnect harness connectors at ACT and ECA. If connectors and terminals are okay, replace sensor and repeat QUICK TEST  . If no fault indicated, go to next step.
  12. Observe volt/ohmmeter while performing the following: Beginning at ACT, 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.
  13. Turn ignition off and wait 10 seconds. Disconnect 60-pin connector at ECA and inspect connector and terminals for damage. If damaged, service as required and repeat QUICK TEST  . If okay, fault cannot be duplicated at this time. Continuous Code 54 and 64 testing is complete.
Fig 1: Air Charge Temperature (ACT) Sensor Circuit
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