Upshift Control and Torque Converter Clutch (TCC) Apply
WARNING: This page is about a different car, the 2003 GMC Yukon XL, 2003 Chevrolet Suburban, and 2003 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
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:
- Refer to Shift Speed, See Shift Speed and choose a throttle position of 10 percent, 25 percent or 50 percent. All throttle angles shown should be tested to cover the normal driving range.
- Monitor the following scan tool parameters:
- Throttle angle
- Vehicle speed
- Engine speed
- Output shaft speed
- Commanded gear
- Slip speed
- Solenoid states
- Place the gear selector in the OVERDRIVE position.
- Accelerate the vehicle using the chosen throttle angle. Hold the throttle steady.
- 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 1-2 seconds of the commanded gear change.
- Compare the shift speeds to the Shift Speed table. Refer to Shift Speed, See 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.
- Repeat steps 1-6 to complete all throttle angles.
Important: The TCC will not engage until the engine is in closed loop operation. The vehicle must be in a near-cruise condition, not accelerating or coasting, and on a level road surface.
- Check for TCC apply in THIRD and FOURTH gear. Typical apply speeds in FOURTH gear range from 72-88 km/h (45-55 mph) depending on engine size, engine type and axle ratio.
- 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 .
- Lightly tap and release the brake pedal. The TCC will release.
- 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: