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Electrical Function Check

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Perform this check first, to ensure the electronic transmission components are connected and functioning properly. If these components are not checked, a simple electrical condition could be mis-diagnosed.

  1. Connect the scan tool.
  2. Ensure the gear shift lever is in Park and set the parking brake.
  3. Start the engine.
  4. Verify that the following scan tool data can be obtained and is functioning properly. Data that is questionable may indicate a concern.
    • Engine Speed
    • Transmission Input Speed
    • Transmission Output Speed
    • Vehicle Speed
    • Transmission Fluid Pressure (TFP) Manual Valve Position Switch
    • Transmission Range
    • Commanded Gear
    • Pressure Control (PC) Solenoid Reference Current
    • PC Solenoid Actual Current
    • PC Solenoid Duty Cycle
    • Brake Switch
    • Engine Coolant Temperature
    • Transmission Fluid Temperature
    • Throttle Angle
    • Ignition Voltage
    • 1-2 Shift Solenoid
    • 2-3 Shift Solenoid
    • TCC Solenoid Duty Cycle
    • TCC Slip Speed
  5. Monitor the brake switch signal while depressing and releasing the brake pedal. The scan tool should display:
    • CLOSED when the brake pedal is released.
    • OPEN when the brake pedal is depressed.
    6. NOTE: Harsh engagement may be caused by high idle speed, commanded low PC solenoid current or a default condition caused by certain DTCs that result in maximum line pressure to prevent slippage.
    NOTE: Soft or delayed engagement may be caused by low idle speed, low fluid level, commanded high PC solenoid current or cold transmission fluid.
  6. Check the garage shifts in the following order:
    1. Apply the brake pedal and ensure the parking brake is set.
    2. Move the gear shift lever through the following ranges: Park to Reverse, Reverse to Neutral and Neutral to Drive.
    3. Pause 2-3 seconds in each gear position.
    4. Verify the gear engagements are immediate and not harsh.
  7. Monitor transmission range on the scan tool engine list while performing the following:
    1. Apply the brake pedal and ensure the parking brake is set.
    2. Move the gear shift lever through all ranges.
    3. Pause 2-3 seconds in each range.
    4. Return gear shift lever to Park.
    5. Verify that all gear shift lever positions match the scan tool display.
  8. Check throttle angle input in the following order:
    1. Apply the brake pedal and ensure the parking brake is set.
    2. Ensure the gear shift lever is in Park.
    3. Monitor throttle angle while increasing and decreasing engine speed with the throttle pedal. The scan tool throttle angle should increase and decrease with engine speed.

If any of the above checks do not perform properly, record the result for reference after completion of the road test.

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