TTEC 4825 Transmission on the road.

                                        Nissan "Cefiro". Transmission

TCC: Torque converter clutch
ECT: Engine coolant temperature
PCM: Power train control module
PSA: Pressure Switch assembly
TPS: Throttle position sensor
TTS: Transmission temperature sensor
VSS: Vehicle speed sensor

                                            make some choice of test

                              Rear gear ON, solenoids valves A-ON, B-ON

                           Solenoid valves in Parking/Neutral position idle
                                solenoids A-ON, B-ON, over run-OFF

                 Lever position in Drive, Three solenoids valves are ON.

                                                            7 km/h
                     The car is running in first gear, all three valves are ON

Second Gear, valves A-OFF, B-ON, over run-ON, open a littlebit throttle position 0.3V

                        Third gear the throttle is closed, speed is 20 km/h
                                Valves A-OFF, B-OFF, over run-ON

The engine accelerated, throttle open 1.3V, transmission is back to second gear

                                In cruise, the transmission in third gear
 

                                       Fourth gear in cruise, valves are OFF

Accelerating from fourth gear, back to third, position of valves are confirm it

Valves A-ON, B-OFF,over run ON. Transmission in over drive. The throttle is closed

                  Slightly accelerating, no change, throttle open 1.5V,speed is 84 km/h

                        In cruise the transmission in O/D, no change

                        Acceleration, fourth gear starts to work again

              
                                 In cruise, the O/D gear comes again

It is perfect example what's going on and how the transmission works

Electronic transmission controls

Numerous changes have occurred in transaxles and transmissions in the last decade. The demand for lighter, smaller and more fuel efficient vehicles has resulted in the use of electronics to control both the engine and transmission to achieve the fuel efficient results that are required by law. The transaxle/transmission assembly is a part of the electronic controls, by sending signals of vehicle speed to an on-board computer which, in turn, relates these signals, along with others from the engine assembly, to determine gear selection for the best performance.

Sensors are used for engine and road speeds, engine load, gear selector lever position, and the kick down switch operation. In addition, the driving program, set by the factory, is used to send signals to the microcomputer to determine the optimum gear selection, according to a preset program. The electrical part of the equation is usually the solenoids and electrically controlled valves that open and close to allow hydraulic fluid pressure to flow in the desired direction and accomplish a specific task.

The electronics also control the modulated hydraulic pressure during shifting, along with regulating engine torque to provide smooth shifts between gear ratio changes. This type of system can be designed for different driving programs, such as giving the operator the choice of operating the vehicle for either economy or performance.

The transmission's sensors also let the operator of the vehicle know if there are any problems with the system. If the transmission control computer detects a problem it will store a trouble code in memory and it will light or flash a transmission warning lamp (or engine service light) on the dash to alert the operator something is wrong.

Two transmission codes out of repair information; 
Code 45 Damaged or disconnected wiring of the pressure-control solenoid valve

system what the code means Check the solenoid valve connector, check 

the pressure - control solenoid valve itself.

Code 24 Damaged or disconnected wiring of the oil-temperature sensor system
Check the oil-temperature sensor connector, and the sensor itself.

Code: LR solenoid Valve Open
This is open because the cable is unplugged

Code: O/D Solenoid Valve Open
This is open due to the cable is unplugged and car is in the 3rd gear.

1st Problem Testing:
With the vehicle stuck in 3rd gear, we tried shifting the car into different gear
but because all the solenoid valves were stuck open and would not close
therefore the vehicle would not shift and remains in the 3rd gear.

2nd Problem Testing:
During the 2nd test we plugged the cables back into the transmission and
started the car and then we were able to change the gears up and down.
I then used the scan tool to check if the valves were closing or not when
we changed the gears and it did.

Shift Solenoid Malfunction: Describe what would happen if none of the solenoids came "ON". Could the vehicle drive? What gear would it be in?

How fast could the vehicle go? Could it have the Power to climb a hill?
According to the vehicle if all the solenoids were off then the only available gear on the vehicle would be 3rd gear to be used. This is because the 3rd gear does not need any solenoids to be "on" therefore the vehicle will be slow during the initial start and can only use 3rd gear. The vehicle would drive up the hill only if the vehicle is on running start.

Using the proper scan tools or techniques, a technician can retrieve the code
(depending on the manufacturer) in order to help diagnose the trouble.
To get a better understanding of engine and transmission trouble codes, in repair
manual for that year/make/model car.