Gear - Drive Mode

The OSC function is used to test the transmission gear changes. The advantage of using OSC for changing gears is to allow the technician to easily test a specific gear and UPSHIFT or DOWNSHIFT concerns that have been identified by the customer. When using OSC to command a shift change, the PCM should command the correct or normal pressure for that shift. The transmission will remain in the gear that the OSC has commanded until the OSC commands another gear or the OSC is cancelled.

The OSC functions for the GEAR parameter allow the technician to choose the following options:

• 1 - Directs the PCM to command 1st gear
• 2 - Directs the PCM to command 2nd gear
• 3 - Directs the PCM to command 3rd gear
• 4 - Directs the PCM to command 4th gear
• XXX - Cancels the OSC command for GEAR and returns to normal operation

The vehicle requirements MUST BE MET when SENDING the OSC value for GEAR. If the vehicle requirements are NOT MET when SENDING the OSC value, an ERROR MESSAGE will appear. When the ERROR MESSAGE is received, OSC is aborted and must be restarted. After SENDING the OSC value, if the vehicle requirements are no longer met, the ERROR MESSAGE will NOT appear, but the PCM will cancel the OSC value. The OSC value XXX may be sent anytime to cancel OSC.

It is recommended to use the TCC parameter in OSC to first turn OFF the torque converter clutch when testing the transmission gear changes. This will allow the technician to evaluate just the gear changes. If the torque converter clutch is not turned OFF, the PCM may command the torque converter clutch to lock during a shift. This could make it more difficult for the technician to determine whether a bad shift is the result of the torque converter clutch changing or the actual gear change.

The vehicle requirements for SENDING an GEAR value are as follows:

• Engine is running
• Gear selector is in OVERDRIVE
• Vehicle speed is greater than 2 MPH
• Vehicle speed must be lower than 30 MPH to command a downshift to 1st gear
• Vehicle speed must be lower than 60 MPH to command a downshift to 2nd gear
• Vehicle speed must be lower than 90 MPH to command a downshift to 3rd gear
• Vehicle speed must be greater than 30 MPH to command an upshift to 4th gear