Transmission Electronic Control System
Transmission Electronic Control System
The powertrain control module (PCM) and its input/output network control the following transmission operations:
- Shift timing
- Line pressure (shift feel)
- Torque converter clutch
The transmission control is separate from the engine control strategy in the PCM, although some of the input signals are shared.
The powertrain control module receives some input signals from engine-related sensors:
- Mass air flow sensor (MAF sensor)
- Engine coolant temperature sensor (ECT sensor)
These signals provide information to the powertrain control module about the load and climate under which the engine is operating. Some inputs are based on driver inputs, such as accelerator pedal position, which is related to the powertrain control module by the throttle position sensor (TP sensor). Still other inputs are provided by:
- Transmission components
- Output shaft speed sensor
- Transmission range (TR) sensor (controlled by driver placement of the shift lever)
- Transmission fluid temperature (TFT) sensor
Using all of these input signals, the powertrain control module can determine when the time and conditions are right for a shift or torque converter clutch application. The powertrain control module can also determine the line pressure needed to optimize shift feel. To accomplish these functions, the powertrain control module controls four electronic solenoids:
- Two on/off shift solenoids
- One pulse-width modulated torque converter clutch solenoid (TCC solenoid) for torque converter clutch (TCC) control or "controlled slip" of the torque converter clutch
- An electronic pressure control (EPC) solenoid for line pressure control
The powertrain control module receives and sends electrical signals that are used to make the transmission more responsive to driver and vehicle needs.
The driver demands are transmitted to the powertrain control module through four components:
- Transmission range selector lever - The driver demand for a particular gear range is translated into an electrical signal for the powertrain control module by the transmission range (TR) sensor.
- Accelerator pedal - The driver demand for torque and acceleration are sent mechanically to the throttle body on the engine. A throttle position sensor then translates this mechanical motion into an electrical signal and sends it to the powertrain control module.
- Brake pedal - A brake on/off (BOO) switch tells the powertrain control module when the brake is applied, indicating the driver demand to disengage the torque converter.
- Transmission control switch - A momentary contact switch, located on the side of the transmission range selector that allows the driver to manually select three or four speed operation.
Shift Solenoid Assembly, Shift Control Solenoids 1 and 2:
Two on/off shift solenoids provide gear selection of first through fourth gears by controlling the pressure to the three shift valves. One unit containing the two shift solenoids is located in the main control valve body. The shift solenoids are two-way, normally open style.
SS-1 Symptoms:
Improper gear selection depending on failure mode and manual lever position.
- Failed ON - first and fourth gear only.
- Failed OFF - second and third gear only.
DTCs:
P0750*, P0751**, P0781**, P0782**, P0783**, P1731, P1732, P1733, P1751
SS-2 Symptoms:
Improper gear selection depending on failure mode and manual lever position.
- Failed ON - third and fourth gear only.
- Failed OFF - first and second gear only.
DTCs:
P0755*, P0756**, P0782**, P0783**, P1732, P1733**, P1756
SS-1 and SS-2 Symptoms:
- Both failed ON - fourth gear only.
- Both failed OFF - second gear only.
DTCs:
P0750*, P0751**, P0755*, P0756
* Output circuit check, generated only by electrical conditions.
** May also be generated by some non-electrical transmission component condition.
Torque Converter Clutch (TCC) Solenoid:
The torque converter clutch solenoid (TCC) is used to control the apply and release of the torque converter clutch.
Symptoms:
- Failed ON - engine stalls in second gear (D, 2 range) at low idle speeds with the brake applied.
- Failed OFF - converter never engages.
DTCs:
P0743*, P1744**, P1741**, P1743, P1742, P0741**
* Output circuit check, generated only by electrical conditions.
** May also be generated by some non-electrical transmission component condition.
Electronic Pressure Control (EPC) Solenoid:
The electronic pressure control (EPC) solenoid regulates transmission EPC (TV) pressure. EPC valve pressure is used to control line pressure and the 2-3 backout valve function.
Symptoms:
- Failed ON - Minimum EPC pressure (minimum capacity), limit engine torque (alternate firing).
- Failed OFF - Maximum EPC pressure, harsh engagements, harsh shifts.
DTCs:
P1746, P1748