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Home >> Ford Truck >> 1998 >> Expedition 4WD V8-281 4.6L SOHC >> Repair and Diagnosis >> Powertrain Management >> Transmission Control Systems >> Testing and Inspection >> Reading and Clearing Diagnostic Trouble Codes >> Special Test Mode >> OSC - Transmission Drive Modes

OSC - Transmission Drive Modes

The DRIVE MODE allows control of three transmission parameters. Each mode/parameter has a unique set of vehicle operating requirements that the technician is required to meet before being allowed to operate OSC. The recommended procedure, when using the DRIVE MODE, is to control one parameter at a time. The DRIVE MODE allows the technician to perform the following functions on the transmission:
- GR_CM - allows upshifts or downshifts.
- TCC - engages or disengages the torque converter clutch.
- EPC - increases/decreases EPC pressure.

GR_CM IN DRIVE MODE
This OSC function is used to test the transmission shift functions.

The OSC functions for the GR_CM parameter allows the technician to choose the following options:
- [1] - PCM selects 1st gear.
- [2] - PCM selects 2nd gear.
- [3] - PCM selects 3rd gear.
- [4] - PCM selects 4th gear.
- [5] - PCM selects 5th gear.

OSC "GR_CM" Mode Operates ONLY when:
- VSS and digital TR Sensor are operational.
- no VSS and digital TR Sensor DTCs.
- engine "ON."
- TCC"OFF."
- transmission range selector lever on O/D.
- vehicle speed is greater than 2 mph.

OSC Command Values
- [1] - PCM selects 1st gear.
- [2] - PCM selects 2nd gear.
- [3] - PCM selects 3rd gear.
- [4] - PCM selects 4th gear.
- [5] - PCM selects 5th gear.
- [OFF] - turns solenoid off.
- [ON] - turns solenoid on.
- [XXX] - cancels OSC value sent.
- [SEND] - sends the values to PCM.

DRIVE MODE PROCEDURE FOR GR_CM
Follow operating instructions from the NGS menu screen.
- Select "Output State Control
- Select "Trans - DRIVE MODE."
- Select "PIDs" to be monitored.
- Monitor all selected PIDs during test.
- Select "Parameters - GR_CM."
- Select Value "1-5."
- Press "SEND" to send command.
- Re-Select Value " 1-5."
- Press "SEND" to send command.
- Select "XXX" to cancel at any time.
- Press "SEND."

TCC IN DRIVE MODE:
This OSC function is used to test whether the torque converter clutch is engaging and disengaging correctly.

The OSC functions for the TCC parameter allows the technician to choose the following:
- TCC - activates TCC OFF and ON.
- [ON] - turns TCC solenoid ON.
- [OFF] - turns TCC solenoid OFF.

OSC "TCC OFF" DRIVE MODE Operates ONLY when:
- VSS and digital TR Sensors are operational.
- No VSS and digital TR Sensor DTCs present.
- Engine ON.
- Transmission range selector lever in O/D.
- Vehicle speed is greater than 2 mph.

OSC "TCC ON" DRIVE MODE Operates ONLY when:
- VSS and digital TR Sensors are operational.
- No VSS and digital TR Sensor DTCs present.
- Engine ON.
- Transmission range selector lever in O/D.
- Vehicle speed is greater than 2 mph.
- Transmission in 2nd gear or higher.
- TFT is between 60 and 275°F.
- Brake not applied "OFF" below 20 mph.
- (Not an excessive load on engine (engine lugging).

OSC Command Values
- [OFF] - turns TCC OFF.
- [ON] - turns TCC ON.
- [XXX] - cancels OSC value sent.
- [SEND] - sends the values to PCM.

DRIVE MODE PROCEDURES FOR TCC
Follow operating instructions from the NGS menu screen.
- Select "Output State Control."
- Select "Traps - Drive Mode."
- Select "PIDs" to be monitored.
- Monitor all selected PIDs during test.
- Select "Parameters - TCC."
- Select "ON" to turn solenoid ON.
- Press "SEND" to send command ON.
- Select "OFF" to turn solenoid OFF.
- Press "SEND" to send command OFF.
- Select "XXX" to cancel at any time.
- Press "SEND."

EPC IN DRIVE MODE
This OSC functions is used to increase the EPC pressure while testing the transmission shift functions. This OSC functions can only increase the EPC pressure greater than what the PCM normally commands. If an OSC value, such as [75] or [90] PSI is sent, the upshifts and downshifts should exhibit a harsher shift. Harsher shifts would indicate that the EPC pressure control works at higher pressures. The best test for the EPC is to use the BENCH MODE and a hydraulic pressure gauge. Using EPC in the BENCH MODE will confirm that the EPC works at both the higher and lower pressures.

The OSC functions for the parameter EPC allows the technician to choose the following options:
- EPC - Activates EPC to selected
- [00] - sets EPC pressure to 00 PSI.
- [15] - sets EPC pressure to 15 PSI.
- [30] - sets EPC pressure to 30 PSI.
- [45] - sets EPC pressure to 45 PSI.
- [60] - sets EPC pressure to 60 PSI.
- [75] - sets EPC pressure to 75 PSI.
- [90] - sets EPC pressure to 90 PSI.

OSC "EPC" 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.
- Key ON.
- Engine ON.
- Vehicle speed greater than 2 mph.
- OSC value for EPC must be greater than what the PCM commands (see EPC PID).

OSC Command Values
- [00] - sets EPC pressure to 00 PSI.
- [15] - sets EPC pressure to 15 PSI.
- [30] - sets EPC pressure to 30 PSI.
- [45] - sets EPC pressure to 45 PSI.
- [60] - sets EPC pressure to 60 PSI.
- [75] - sets EPC pressure to 75 PSI.
- [90] - sets EPC pressure to 90 PSI.
- [OFF] - turns solenoid off.
- [ON] - turns solenoid on.
- [XXX] - cancels OSC value sent.
- [SEND] - sends the values to PCM.

DRIVE MODE PROCEDURE FOR EPC
Follow operating instructions from the NGS menu screen.
- Select "Output State Control."
- Select "Trans - Drive Mode."
- Select "PIDs" to be monitored.
- Monitor all selected PIDs during test.
- Select "Parameters - EPC.
- Select Value "0-90 psi."
- Press "SEND" to send command.
- Re-Select Value "0-90 psi. "
- Press "SEND" to send command.
- Select "XXX" to cancel at any time.
- Press "SEND."
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