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Home › American Motors › 1983 › Spirit DL, Automatic, 904 › Repair and Diagnosis › Engine Performance › System › 4.2L Feedback Carburetor System › Testing › Test No 2 - Initialization Test

Test No 2 - Initialization Test

NOTE: When applicable, diagnostic connector terminals can be used as test point instead of MCU harness connector terminals.
  1. Remove air cleaner. Install plastic safety shield. While observing metering pins, have helper turn ignition switch to start engine.
  2. Metering pins should move fully toward the front of the engine, reverse direction and move back towards rear, reverse direction again and move towards front, then stop and remain stationary. If not, go to step 5. If so, turn ignition off.
  3. Locate thermal electric switch (TES) located on air cleaner and disconnect from wiring harness. Install a jumper wire across wire connector terminals.
  4. Start engine and observe metering pins. Metering pins should repeat initialization process described in step 2. If so, remove jumper wire and connect TES switch. Test is complete. If not, replace MCU and retest.
  5. Turn engine off. Disconnect harness connector at MCU. Test resistance between MCU harness connector J2 pin 11 and MCU harness connector J1 pins 2, 4, 6 and 10. All resistances should be between 50 and 95 ohms. If not, go to step 8.
  6. If so, repeat resistance test using pin 1 of connector J2 instead of pin 11. All resistances should be between 50 and 95 ohms. If not, go to step 8. If so, remove stepper motor and inspect for pin bending. Connect MCU harness with stepper motor removed. Turn on engine and observe pin movement.
  7. When engine is first turned on, stepper motor pins should move to full forward position (rich) and then back to half-way position. If so, repair stepper motor pin binding defect. If not, replace MCU and retest stepper motor.
  8. Turn ignition on and disconnect stepper motor connector. Test for battery voltage at pin 5 of the stepper motor connector. If there is no voltage, repair and retest. If voltage is okay, turn ignition off and test 4 remaining stepper motor connector pins for short to ground.
  9. All should indicate an open circuit. If not okay, repair and retest. If okay, test for continuity between MCU connector pins 2, 4, 6 and 10 and appropriate pins at stepper motor connector for correct color orientation of wires.
  10. If okay, connect MCU harness connector. Replace stepper motor. If not okay, connect MCU harness connector. Repair and start test over.
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