OSC For Transmission - Drive Mode

The Drive Mode allows control of 3 transmission functions. Each function has a unique set of vehicle operating requirements that the technician is required to meet before the PCM will allow OSC to operate. The Drive Mode allows the technician to carry out the following functions:

TCC_OSC - Commands the PCM to engage or disengage the torque converter clutch.
GEAR_OSC - Commands the PCM to upshift or downshift.
HRSH_SFT - Commands a higher pressure value during an upshift.

The OSC options to control TCC_OSC to engage or disengage the torque converter clutch in Drive Mode are as follows:

OFF - Commands the PCM to keep the torque converter clutch from engaging.
ON - Commands the PCM to engage the torque converter clutch.
XXX - Cancels OSC and allows PCM normal control of the torque converter clutch.

Controlling the torque converter clutch will assist the technician in testing the torque converter for engagements and disengagements. Also, the technician is better able to evaluate upshifts and downshifts by using the OSC to keep the torque converter clutch from engaging.

The vehicle requirements must be met when sending the OSC value for TCC_OSC. If the vehicle requirements are not met when sending the OSC value, an error message may appear. When the error message is received, the OSC is aborted and must be restarted. After the OSC value for TCC_OSC is sent, if the vehicle requirements are no longer met, the error message will not appear but the OSC value will be canceled by the PCM (monitor corresponding PID). The OSC value XXX may be sent anytime to cancel OSC.

The vehicle requirements for sending the TCC_OSC value OFF are as follows:

Engine running
Gear selector in overdrive
Vehicle speed greater than 5 km/h (3 mph)

The vehicle requirements for sending the TCC_OSC value ON are as follows:

Engine running
Gear selector in overdrive
Vehicle speed greater than 5 km/h (3 mph)
Transmission fluid temperature (TFT) between 17°C and 135°C (60°F and 275°F)
Brake is off when vehicle speed is below 32 km/h (20 mph)
Not an excessive load on the engine
Engine speed greater than 1,300 RPM

The OSC options to control GEAR_OSC to shift the transmission in Drive Mode are as follows:

1 - Commands PCM to shift to 1st gear auto.
2 - Commands PCM to shift to 2nd gear auto.
3 - Commands PCM to shift to 3rd gear auto.
5 - Commands PCM to shift to 5th gear auto.
6 - Commands PCM to shift to 6th gear auto.
XXX - Cancels OSC and allows PCM normal control of upshifts and downshifts.

Controlling the gear changes will assist the technician in testing the various clutches and bands and determine whether the transmission is slipping in any particular gear. The OSC will command the PCM to upshift or downshift depending on the gear the technician selects. The transmission will remain in the OSC gear selected until another OSC gear is selected or until OSC is cancelled.

NOTE: Fourth gear is not allowed to be commanded when using OSC.

The vehicle requirements must be met when sending the OSC value for GEAR_OSC. If the vehicle requirements are not met when sending the OSC value, an error message may appear. When the error message is received, the OSC is aborted and must be restarted. After the OSC value for GEAR_OSC is sent, if the vehicle requirements are no longer met, the error message will not appear but the OSC value will be canceled by the PCM (monitor corresponding PID). The OSC value XXX may be sent anytime to cancel OSC.

It is recommended to use TCC_OSC to first turn off the torque converter clutch before testing the transmission gear changes. This will allow the technician to evaluate only the gear changes. If the torque converter clutch is NOT turned OFF, the PCM will command the torque converter clutch to engage. This could make it difficult for the technician to determine whether an abnormal shift is the result of the torque converter clutch or the actual gear change.

The vehicle requirements for sending a GEAR_OSC value are as follows:

Engine running
Gear selector in overdrive
Vehicle speed greater than 5 km/h (3 mph)

The OSC options to control HRSH_SFT to moderately increase line pressure to test for firmer engagements and shifts in Drive Mode are as follows:

OFF - Commands PCM to use normal pressure and not to increase hydraulic pressure.
ON - Commands PCM to moderately increase the hydraulic pressure.
XXX - Cancels OSC.

Setting HRSH_SFT allows the technician to moderately increase the pressure when carrying out engagements such as park-to-reverse, neutral-to-reverse, etc., and when carrying out automatic upshifts. This will provide additional diagnostic information to help the technician determine whether the electronic pressure control system is providing at least limited control (a normal shift would become firmer) and/or whether a hydraulic circuit that may have abnormally low pressure (due to such things as low fluid level, leaky clutch, etc.) resulting in a soft shift, becomes normal when increasing the pressure.

The vehicle requirements must be met when sending the OSC value for HRSH_SFT. If the vehicle requirements are not met when sending the OSC value, an error message may appear. When the error message is received, the OSC is aborted and must be restarted. After the OSC value for HRSH_SFT is sent, if the vehicle requirements are no longer met, the error message will not appear but the OSC value will be canceled but the PCM (monitor corresponding PID). The OSC value XXX may be sent anytime to cancel OSC.