GEAR in 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/or upshift or downshift that has been identified as the customer complaint. 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 OSC has commanded until OSC commands another gear or OSC is cancelled.
The OSC functions for the OSCGEAR parameter allow the technician to choose the following options:
- 1 - Directs PCM to command 1st gear
- 2 - Directs PCM to command 2nd gear
- 3 - Directs PCM to command 3rd gear
- 4 - Directs PCM to command 4th gear
The vehicle requirements must be met when sending the OSC command for GEAR. If the vehicle requirements are not met when sending the OSC command, the command will be cancelled. If after sending the OSC command the vehicle requirements are no longer met, the OSC command will be cancelled.
It is recommended to use the TCC parameter in OSC to first turn OFF the 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, then 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 engaging or the actual gear change.
The vehicle requirements for sending a GEAR value is as follows:
- Engine is running
- Gear selector is in OVERDRIVE
- Vehicle speed is greater than 3 km/h (2 mph)
- Vehicle speed must be lower than 48 km/h (30 mph) to command a downshift to 1st gear
- Vehicle speed must be lower than 97 km/h (60 mph) to command a downshift to 2nd gear
- Vehicle speed must be lower than 145 km/h (90 mph) to command a downshift to 3rd gear
- Vehicle speed must be greater than 48 km/h (30 mph) to command an upshift to 4th gear