Functional Operation

FUNCTIONAL OPERATION
The 42LE electronic transaxle has a fully adaptive control system. The system performs it's functions based on continuous real-time sensor feedback information. The control system automatically adapts to changes in engine performance and friction element variations to provide consistent shift quality. The control system ensures that clutch operation during upshifting and downshifting is more responsive without increased harshness.
The Transmission Control Module (TCM) continuously checks for electrical problems, mechanical problems, and some hydraulic problems. When a problem is sensed, the TCM stores a diagnostic trouble code. Some of these codes cause the transaxle to go into limp-in or A default mode. While in this mode, electrical power is taken away from the transaxle via the TCM, de-energizing the transmission control relay, and taking power from the solenoid pack.
When this happens, the only transaxle functions are:
- Park and Neutral
- Reverse
- Second Gear
No upshifts or downshifts are possible. The position of the manual valve alone allows the three ranges that are available. Although vehicle performance is seriously degraded while in this mode, it allows the owner to drive the vehicle in for service.
Once the DRBIII(R) is in the EATX portion of the diagnostic program, it constantly monitors the TCM to see if the system is in limp-in mode. If the transaxle is in limp-in mode, the DRBIII(R) will flash the red LED.

AUTOSTICK FEATURE
This feature allows the driver to manually shift the transaxle when the shift lever is pulled back into the AutoStick position. When in AutoStick, the instrument cluster displays the current gear.

TRANSMISSION OPERATION AND SHIFT SCHEDULING AT VARIOUS OIL TEMPERATURES
The transmission covered in this section has unique shift schedules depending on the temperature of the transmission oil. The shift schedule is modified to extend the life of the transmission while operating under extreme conditions.
The oil temperature is measured with a Transmission Temperature Sensor on the 42LE transmission. The Transmission Temperature Sensor is an integral component of the Transmission Range Sensor (TRS). If it is faulty, (DTC P1799(74)) the transmission will default to a calculated oil temperature. Oil temperature will then be calculated through a complex heat transfer equation which uses engine coolant temperature, battery/ambient temperature, and engine off time from the Body Control Module (BCM). These inputs are received from the bus periodically and used to initialize the oil temperature at start up. Once the engine is started, the TCM updates the transmission oil temperature based on torque converter slip speed, vehicle speed, gear, and engine coolant temperature to determine an estimated oil temperature during vehicle operation. Vehicles using A calculated oil temperature track oil temperature reasonably accurate during normal operation. However, if a transmission is overfilled, a transmission oil cooler becomes restricted, or if a customer drives aggressively in low gear, the calculated oil temperature will be inaccurate. Consequently the shift schedule selected may be inappropriate for the current conditions. The key highlights of the various shift schedules are as follows:
Extreme Cold: Oil temperature at start up below 26.6C (- 16°F)
> Goes to a Cold schedule above - 12°F oil temperature
> Park, Reverse, Neutral and 2nd gear only (prevents shifting which may fail a clutch with frequent shifts)
Cold: Oil temperature at start up above -24.4 C ( - 12°F) and below 2.2 C (36°F)
- Goes to a Warm schedule above 4.4 C (40°F) oil temperature
- Delayed 2-3 upshift (approximately 22-31 MPH)
- Delayed 3-4 upshift (45 - 53 MPH)
- Early 4-3 coastdown shift (approximately 30 MPH)
- Early 3-2 coastdown shift (approximately 17 MPH)
- High speed 4-2, 3-2, 2-1 kickdown shifts are prevented
- No EMCC
Warm: Oil temperature at start up above 2.2 C (36°F) and below 26.6 C (80°F)
- Goes to a Hot schedule above 26.6 C (80°F) oil temperature
- Normal operation (upshifts, kickdowns, and coastdowns)
- No EMCC
Hot: Oil temperature at start up above 26.6 C (80°F)
- Goes to an Overheat schedule above 115.5 C (240°F) oil temperature
- Normal operation (upshifts, kickdowns, and coastdowns)
- Full EMCC, No PEMCC except to engage
- FEMCC (Except at closed throttle at speeds above 112.6 Km/h (70 MPH) - 133.5 Km/h (83 MPH)
Overheat: Oil temperature above 115.5 C (240°F) or engine coolant temperature above 117.7 C (244°F)
- Goes to Hot below 110.0 C (230°F) oil temperature or Super Overheat above 115.5 C (240°F) oil temperature
- Delayed 2-3 upshift 40 - 52 Km/h (25 - 32 MPH)
- Delayed 3-4 upshift 67 - 77 Km/h (41 - 48 MPH)
- 3rd gear FEMCC from 48 - 77 Km/h (30 - 48 MPH)
- 3rd gear PEMCC from 43 - 50 Km/h (27 - 31 MPH)
Super Overheat: Oil temperature above 126.6 C (260°F)
- Goes back to Overheat below 115.5 C (240°F) oil temperature
- All Overheat shift schedules features apply 2nd gear PEMCC above 35.5 Km/h (22 MPH)
- Above 22 MPH the torque converter will not unlock unless the throttle is closed (i.e. at 80 Km/h (50 MPH) a 4th FEMCC to 3rd FEMCC shift will be made during a part throttle kick - down or a 4th FEMCC to 2nd PEMCC shift will be made at wide open throttle) or if a wide open throttle 2nd PEMCC to 1 kickdown is made.
Causes for operation in the wrong temperature shift schedule:
Extreme Cold or Cold shift schedule at start up:
- Defective Transmission Temperature Sensor circuit.
Overheat or Super Overheat shift schedule after extended operation:
- Operation in city traffic or stop and go traffic
- Engine idle speed too high
- Aggressive driving in low gear
- Trailer towing in OD gear position (use A3" position (or A/S 3rd) if frequent shifting occurs)
- Cooling system failure causing engine to operate over 110 C (230°F)
- Engine coolant temperature stays low too long - If engine coolant temperature drops below 65.5 C (150°F), the transmission will disengage EMCC. Extended operation with the EMCC disengaged will cause the transmission to overheat.
- A defective brake switch will cause the EMCC to disengage. Extended operation with the EMCC disengaged will cause the transmission to overheat.
- Transmission fluid overfilled
- Transmission cooler or cooler lines restricted
- Defective Transmission Temperature Sensor circuit