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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 505 (Automatic Transmission - 2ML70 - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> Road Test >> Electrical Function Check

Electrical Function Check

WARNING: This page is about a different car, the 2012 GMC Yukon, 2012 Chevrolet Tahoe, and 2012 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.

Perform this procedure first in order to ensure the electronic transmission components are functioning properly. If these components are not checked, a simple electrical condition could be misdiagnosed.

  1. Connect the scan tool.
  2. Ensure the gear selector is in PARK and set the parking brake.
  3. Start the engine.
    NOTE:

    Note that the engine may go in to AutoStop Mode depending on which gear is selected and many other variables. For more information on AutoStop Mode refer to Hybrid Modes of Operation Description .

  4. Verify that the following scan tool data can be obtained and is functioning properly.

    Refer to Control Module References for typical data values. Data that is questionable may indicate a concern.

    • Engine Torque
    • Drvr Axle Torque Request
    • APP Indicated Angle
    • Engine Speed
    • Calc. Trans Input Speed
    • Transmission OSS
    • OSS Supply Voltage
    • Vehicle Speed
    • Output Shaft Direction
    • Clutch 1 Slip Speed
    • Clutch 2 Slip Speed
    • Clutch 3 Slip Speed
    • Clutch 4 Slip Speed
    • Clutch 1 Status
    • Clutch 2 Status
    • Clutch 3 Status
    • Clutch 4 Status
    • IAT
    • BPP Signal
    • Shift Solenoid 1
    • Shift Solenoid 2
    • Gear Ratio
    • Driver Shift Control
    • Driver Shift Request
    • IMS A/B/C/P
    • IMS
    • TFP Switch 1
    • TFP Switch 3
    • TFP Switch 4
    • TFP Switch 5
    • ECT
    • Trans. Fluid Temp.
    • TCM Temperature
    • PC Sol. 2 Pressure Cmd.
    • PC Sol. 3 Pressure Cmd.
    • PC Sol. 4 Pressure Cmd.
    • PC Sol. 5 Pressure Cmd.
    • Line PC Sol. Pressure Cmd.
    • Engine Run Time
    • EC Ignition Relay Feedback Signal
    • Ignition Voltage
  5. Check the garage shifts.
    1. Apply the brake pedal and ensure the parking brake is set.
      NOTE:

      If the vehicle was in the AutoStop Mode the engine will start and run when the gear selector is placed in Reverse and M (Manual). If the gear selector is moved very quickly through these ranges and is in the AutoStop Mode the engine will not restart.

    2. Move the gear selector through the following ranges: Pause 2 to 3 seconds in each gear position.
      1. PARK to REVERSE
      2. REVERSE to NEUTRAL
      3. NEUTRAL to DRIVE
    3. Verify the gear engagements are immediate and not harsh.
      NOTE:

      These shifts can not be felt when trans is functioning properly.

  6. NOTE:

    Harsh engagement may be caused by any of the following conditions:

    • High engine idle speed-Compare engine idle speed to desired idle speed.
    • Commanded low pressure control (PC) solenoid current-Investigate PC Sol. Pressure Cmd. kPa (psi) for all solenoids. High pressure will cause harsh shifts.
    • A default condition caused by certain DTCs that result in maximum line pressure to prevent clutch slippage.
    NOTE:

    Soft or delayed engagement may be caused by any of the following conditions:

    • Low idle speed-Compare engine idle speed to desired idle speed
    • Low auxiliary pump pressure in autostop only
    • Low fluid level
    • Commanded high PC solenoid current-Investigate PC Sol. Pressure Cmd. kPa (psi) for all solenoids. Low pressure will cause soft or delayed shifts
    • Cold transmission fluid temperature (TFT)-Use the scan tool to determine TFT
    • Selector linkage-Inspect and adjust as necessary
  7. Monitor transmission range on the scan tool, trans data list.
    1. Apply the brake pedal and ensure the parking brake is set.
    2. Move the gear selector through all ranges. Pause 2 to 3 seconds in each range.
    3. Return gear selector to PARK.
    4. Verify that all selector positions match the scan tool display.
  8. Check throttle position input.
    1. Apply the brake pedal and ensure the parking brake is set.
    2. Ensure the gear selector is in PARK.
    3. Monitor the scan tool Calc. Throttle Position while increasing and decreasing engine speed with the throttle pedal. The scan tool Calc. Throttle Position percentage 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.