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Circuit/System Testing

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PNP Switch Malfunction (MYC 6L80E, MYD 6L90E)

  1. Inspect the range selector lever cable for proper adjustment. Refer to Range Selector Lever Cable Adjustment .
  2. Ignition OFF. Disconnect the 16-way harness connector from the transmission.
  3. Ignition ON. Measure voltage on the park/neutral signal circuit terminal 3 with a DMM. Verify that there is greater than 10 V on the park/neutral signal circuit.
    • If there is less than 10 V on the park/neutral signal circuit, test the circuit for an open or a short to ground. If OK, replace the ECM.
  4. Ignition OFF, reconnect the 16-way harness connector to the transmission.
  5. Remove the automatic transmission fluid pan. Refer to Automatic Transmission Fluid, Fluid Pan and/or Filter Replacement .
  6. Disconnect the manual shift shaft position switch connector at the control solenoid valve assembly. Refer to Manual Shift Shaft Position Switch Replacement .
  7. Ignition ON, verify that the scan tool PNP Switch parameter displays In Gear.
    • If not the specified value, replace the ECM.
  8. Connect a 3 A fused jumper wire between the park/neutral signal terminal F at the control solenoid valve assembly and ground. The scan tool PNP Switch parameter should display Park/Neutral when the terminal is connected to ground.
    • If not the specified value, replace the ECM.
  9. If all components test normal, test or replace the manual shift shaft position switch.

STRTR Relay Malfunction

  1. Ignition OFF, disconnect the STRTR relay.
  2. Ignition ON, transmission in Park/Neutral. Verify that a test lamp illuminates between the relay coil ground circuit terminal and B+.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Probe the STRTR Relay switch B+ circuit terminal with a test lamp that is connected to ground. Verify that the test lamp illuminates.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the STRTR fuse is open, test the relay controlled output circuit for a short to ground.
  4. Connect a test lamp between the relay coil ground circuit terminal and the relay coil control circuit terminal.
    5. NOTE:

    The engine may begin to crank.

  5. Ignition ON, transmission in Park/Neutral. Command the Starter Relay ON and OFF with a scan tool, or turn the ignition switch between the START and RUN positions. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the relay coil control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    • If the test lamp is always OFF, test the relay coil control circuit for a short to ground or and open/high resistance. If the circuit tests normal, replace the ECM.
  6. Connect the START relay.
  7. Install a test lamp between the starter terminal S X2 and ground.
    8. NOTE:

    The engine may begin to crank.

  8. Ignition ON, transmission in Park/Neutral, command the Starter Relay ON with a scan tool, or turn the ignition switch to the START position. The test lamp should illuminate.
    • If the test lamp does not illuminate, test the relay controlled output circuit for an open/high resistance. If the circuit tests normal, test or replace the STRTR relay.
  9. If all circuits test normal, test or replace the starter.
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