Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Electronic Transaxle
The transaxle is controlled by the Powertrain Control Module (PCM). PCM controls other vehicle functions as well as the transmission. The PCM controls shift points by means of two shift solenoids. A third solenoid controls the application of the Torque Converter Clutch. A gear driven oil pump supplies the oil pressure. The PCM regulates oil pressure by means of a pressure control solenoid valve.
- Shift Solenoid No. 1
Shift solenoid No. 1 and shift solenoid No. 2 are used together to electronically control the shifting of the transaxle from 1st gear to 4th gear/overdrive. The PCM outputs system voltage to turn ON (energize) or remove voltage to turn OFF (de-energize) either solenoid when it deems necessary. The transaxle shifts with the combination of both solenoids being turned ON and OFF. Shift solenoid No. 1 is normally ON in 1st and 2nd gears and never ON in 3rd or 4th gears. Shift solenoid No. 2 is normally ON in 2nd and 3rd gears and never ON in 1st or 4th gears. 4th gear/overdrive is obtained when both shift solenoids are OFF. - Shift Solenoid No. 2
Shift solenoid No. 2 is energized and de-energized by the PCM in response to varying transaxle shift demands. With the shift solenoid No. 2 de-energized, line pressure is applied to the 1-2 shift valve. With the line pressure applied, the 1-2 shift operates, and the transaxle shifts from second to third gear. When the PCM energizes the shift solenoid No. 1, line pressure is relieved, and the 1-2 shift valve does not operate. - Pressure Control Solenoid
Pressure Control (PC) solenoid is attached to the valve body and controls line pressure by moving a pressure regulator valve against spring pressure. PCM varies line pressure based upon engine load. Engine load is calculated from several inputs including Manifold Absolute Pressure (MAP) sensor, Transmission Fluid Temperature (TFT) sensor, Throttle Position (TP) sensor and gear position. Line pressure is actually varied by changing the amperage applied to pressure control solenoid from .02 (maximum pressure) to 1.1 amps (minimum pressure). The PCM continuously varies the PC solenoid valve amps to maintain the correct average current flowing through the valve.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.