Electrical Function Check: Notes

Perform this check first, in order 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 selector 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.

   Refer to TRANSMISSION SCAN TOOL DATA LIST  for typical data values. Data that is questionable may indicate a concern.

   • Engine Speed
   • Transmission output speed
   • Vehicle speed
   • TFP manual valve position switch
   • Transmission range, engine list
   • Commanded gear, current gear
   • 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. Check the garage shifts.
   1. 6.1. Apply the brake pedal and ensure that the parking brake is set.
   2. 6.2. Move the gear selector through the following ranges:
      1. 6.2.1. PARK to REVERSE
      2. 6.2.2. REVERSE to NEUTRAL
      3. 6.2.3. NEUTRAL to DRIVE
   3. Pause 2 to 3 seconds in each gear position.
   4. Verify the gear engagements are immediate and not harsh.

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

   • High idle speed. Compare engine idle speed to desired idle speed.
   • Commanded low PC solenoid current. Compare PC solenoid reference current to PC solenoid actual current.
   • A default condition caused by certain DTCs that result in maximum line pressure to prevent slippage.

   Important:  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 fluid level
   • Commanded high PC solenoid current. Compare PC solenoid reference current to PC solenoid actual current.
   • Cold transmission fluid. Check for low transmission fluid temperature.
7. Monitor transmission range on the scan tool, engine list.
   1. 7.1. Apply the brake pedal and ensure the parking brake is set.
   2. 7.2. Move the gear selector through all ranges.
   3. 7.3. Pause 2 to 3 seconds in each range.
   4. 7.4. Return gear selector to PARK.
   5. 7.5. Verify that all selector positions match the scan tool display.
8. Check throttle angle input.
   1. 8.1. Apply the brake pedal and ensure that the parking brake is set.
   2. 8.2. Ensure the gear selector is in PARK.
   3. 8.3. 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.

   Upshift Control and Torque Converter Clutch (TCC) Apply 

   The PCM calculates the upshift points based primarily on two inputs: throttle angle and vehicle speed. When the PCM determines that conditions are met for a shift to occur, the PCM commands the shift by closing or opening the ground circuit for the appropriate solenoid.

   Perform the following steps:

1. Refer to the SHIFT SPEED  table in this section and choose a throttle position of 12 percent, 25 percent or 50 percent. All throttle angles shown should be tested to cover the normal driving range.
2. Monitor the following scan tool parameters:
   • Throttle angle
   • Vehicle speed
   • Engine speed
   • Output shaft speed
   • Commanded gear
   • Slip speed
   • Solenoid states
3. Place the gear selector in the OVERDRIVE position.
4. Accelerate the vehicle using the chosen throttle angle. Hold the throttle steady.
5. As the transmission upshifts, note the vehicle speed when the shift occurs for each gear change. There should be a noticeable shift feel or engine speed change within 1 to 2 seconds of the commanded gear change.
6. Compare the shift speeds to the Shift Speed table. Refer to SHIFT SPEED . Shift speeds may vary slightly due to transmission fluid temperature or hydraulic delays in responding to electronic controls.
   • Note any harsh, soft or delayed shifts or slipping.
   • Note any noise or vibration.
7. Repeat steps 1 through 6 to complete all throttle angles.

   Important:  This transmission is equipped with an electronically controlled capacity clutch (ECCC). The pressure plate does not fully lock to the torque converter cover. Instead, the pressure plate maintains a small amount of slippage, about 20 RPM, in SECOND, THIRD and FOURTH gears, depending on the vehicle application. ECCC was developed to reduce the possibility of noise, vibration or chuggle caused by TCC apply. Typical apply speeds are 49-52 km/h (30-32 mph) in THIRD gear and 65-73 km/h (40-45 mph) in FOURTH gear. Full lockup is available at highway speeds on some applications.

   Important:  The TCC will not engage until the engine is in closed loop operation and the vehicle speed is as shown in the Shift Speed table. Refer to SHIFT SPEED . The vehicle must be in a near-cruise condition, not accelerating or coasting, and on a level road surface.

8. Check for TCC apply in THIRD and FOURTH gear.
   • Note the TCC apply point. When the TCC applies there should be a noticeable drop in engine speed and a drop in slip speed to below 100 RPM. If the TCC apply can not be detected:
     • Check for DTCs.
     • Refer to TORQUE CONVERTER DIAGNOSIS PROCEDURE .
     • Refer to the SHIFT SPEED  table for the correct apply speeds.
     • Lightly tap and release the brake pedal. The TCC will release on most applications.