Electrical Function Check
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
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.
- Install the scan tool.
- Ensure the shift selector is in PARK and set the parking brake.
- Start the engine.
- Verify that the following scan tool data can be obtained and is functioning properly. Refer to Scan Tool Data List
for typical data values. Data that is questionable may indicate a concern.
- Engine speed
- Transmission input speed, turbine
- Transmission output speed
- Vehicle speed
- C, D, E and REVERSE pressure switch states
- Transmission range, engine list
- 4WD low
- Commanded range, current range
- A and B solenoid reference current
- A and B solenoid actual current
- A and B solenoid duty cycle
- Brake switch
- Engine coolant temperature
- Transmission fluid temperature
- Throttle angle
- Ignition voltage
- C shift solenoid ON/OFF
- D shift solenoid ON/OFF
- E shift solenoid ON/OFF
- TCC solenoid duty cycle
- TCC slip speed
- Monitor the brake switch signal while depressing and releasing the brake pedal. The scan tool should display the following:
- Closed when the brake pedal is released
- Open when the brake pedal is depressed
- Check the garage shifts.
- Apply the brake pedal and ensure the parking brake is set.
- Move the shift selector through the following ranges:
- PARK to REVERSE
- REVERSE to NEUTRAL
- NEUTRAL to DRIVE
- Pause 2 to 3 seconds in each selector position.
- High idle speed
Compare engine idle speed to desired idle speed.
- Commanded low A or B solenoid current
Compare A and B solenoid reference current to A and B solenoid actual current.
- A default condition caused by certain DTCs that result in maximum full throttle shift points
- Shift is not fully adapted
- Low idle speed
Compare engine idle speed to desired idle speed.
- Low fluid level
- Cold transmission fluid
Inspect for low transmission fluid temperature.
- Verify the range engagements are immediate and not harsh.
IMPORTANT: Harsh engagement may be caused by any of the following conditions:IMPORTANT: Soft or delayed engagement may be caused by any of the following conditions: - Monitor the transmission range on the scan tool engine list.
- Apply the brake pedal and ensure the parking brake is set.
- Move the shift selector through all ranges.
- Pause 2 to 3 seconds in each range.
- Return the shift selector to PARK.
- Verify that all of the selector positions match the scan tool display.
- Inspect the throttle angle input.
- Apply the brake pedal and ensure the parking brake is set.
- Ensure the shift selector is in PARK.
- Monitor the throttle angle while increasing and decreasing the engine speed with the throttle pedal. The scan tool throttle angle should increase and decrease with the engine speed.
If any of the above checks do not perform properly, record the result for reference after the completion of the Road Test Procedure.