FIRM_SFT in Drive Mode
This OSC function is used to raise pressure during an upshift to determine whether the pressure control system is functioning correctly. Harsher shifts indicate that the pressure control system works at higher pressure. The best test for isolating pressure control system problems is to carry out the PCA, PCB, PCC in BENCH Mode using a hydraulic pressure gauge.
The OSC functions for the parameter FIRM_SFT allows the technician to choose the following options:
- FIRM_SFT - Activates the harsh shift channel.
- ON - Sets control pressure higher for all upshifts (determined by the PCM).
- OFF - Sets control pressure to normal for all upshifts (determined by the PCM).
- XXX - Cancels OSC for FIRM_SFT.
OSC "FIRM_SFT" DRIVE Mode operates ONLY when:
- VSS and digital TR sensor are operational.
- No VSS and digital TR sensor DTCs.
- Transmission range selector lever in O/D.
- Pressure gauge installed (optional).
- Key ON.
- Engine ON.
- Vehicle speed greater than 3 km/h (2 mph).
- TCC is OFF (TCC is not engaged).
OSC Command Values:
- ON - Sets control pressure high for all upshifts (determined by the PCM).
- OFF - Sets control pressure to normal for all upshifts (determined by the PCM).
- XXX - Cancel OSC for FIRM_SFT.
- SEND - Sends the values to the PCM.
DRIVE Mode procedure for FIRM_SFT
Follow operating instructions from the scan tool menu screen.
- Select "Output State Control".
- Select "Trans - Drive Mode".
- Select "PIDs" to be monitored.
- Monitor all selected PIDs during test.
- Select "Parameters - FIRM_SFT."
- Press "SEND" to send command.
- Select "XXX" to cancel at any time.
- Press "SEND."
Using Output State Control (OSC) and Accessing PIDs
To confirm that the OSC value was sent by the scan tool and the PCM has accepted the OSC substitution, a corresponding PID for each OSC parameter must be monitored. Additional PIDs should be monitored to help the technician adequately diagnose the transmission.
The following is a list of OSC parameters and their corresponding PID:
| Corresponding PID | Description |
|---|---|
| BPP | Brake Pedal Position Switch On/Off |
| PCA | Pressure Control Solenoid A - Commanded Pressure |
| PCB | Pressure Control Solenoid B - Commanded Pressure |
| PCC | Pressure Control Solenoid C - Commanded Pressure |
| FIRMST | Firm Shift Control (FMC) Status Requested by OSC; 0 = FSC not Commanded by OSC, NGS PID Output = OFF; 1 = FSC Commanded by OSC, NGS PID Output = ON |
| GEAR | Commanded Transmission Gear (use in DRIVE only) |
| RPM | Engine Revolutions Per Minute |
| SSA | Shift Solenoid A Commanded ON |
| SSB | Shift Solenoid B Commanded ON |
| SSC | Shift Solenoid C Commanded ON |
| SSD | Shift Solenoid D Commanded ON |
| TCC | Torque Converter Commanded Duty Cycles (%) |
| TCCRAT | Torque Converter Speed Ratio (RPM and/or TSS) |
| TFT | Transmission Fluid Temperature (degrees Fahrenheit) |
| VSS | Vehicle Speed (mph) |
To confirm that the OSC substitution occurred, SEND the OSC value and monitor the corresponding PID value. If no ERROR MESSAGE was received and the value of the corresponding PID is the same as the value sent from OSC, then the OSC substitution was successful.