Shift Solenoid: Description and Operation

1-2 AND 2-3 SHIFT SOLENOID VALVES

IMPORTANT: The shift solenoid valve resistance should measure 19-24 ohms minimum when measured at 20°C (68°F). The shift solenoid current flow should not exceed 0.75 amps. The shift solenoid should energize at a voltage of 7.5 volts or more (measured across the terminals). The shift solenoid should de-energize when the voltage is one volt or less. If both solenoids lose power, third gear only results.
The 1-2 and 2-3 shift solenoid valves (also called A and B solenoids) are identical devices that control the movement of the 1-2 and 2-3 shift valves (the 3-4 shift valve is not directly controlled by a shift solenoid). The solenoids are normally open exhaust valves that work in four combinations to shift the transmission into different gears.
The Powertrain Control Module (PCM) energizes each solenoid by grounding the solenoid through an internal quad driver. This sends current through the coil winding in the solenoid and moves the internal plunger out of the exhaust position. When ON, the solenoid redirects fluid to move a shift valve.
The PCM-controlled shift solenoids eliminate the need for TV and governor pressures to control shift valve operation.

IMPORTANT: The manual valve hydraulically can override the shift solenoids. Only in D4 do the shift solenoid states totally determine what gear the transmission is in. In the other manual valve positions, the transmission shifts hydraulically and the shift solenoid states CATCH UP when the throttle position and the vehicle speed fall into the correct ranges. Diagnostic trouble codes P0753 and P0758 indicate shift solenoid circuit voltage faults.






3-2 SHIFT SOLENOID VALVE ASSEMBLY

IMPORTANT: The 3-2 shift solenoid valve assembly resistance should be a minimum of 20-24 ohms at 20°C (68°F). The 3-2 shift solenoid valve assembly is an ON/OFF solenoid that is used in order to improve the 3-2 downshift. The solenoid regulates the release of the 3-4 clutch and the 2-4 band apply. If a voltage fault is detected in the 3-2 shift solenoid circuit, diagnostic trouble code P0785 will set.






TRANSMISSION PRESSURE CONTROL SOLENOID

IMPORTANT: Transmission pressure control solenoid resistance should measure 3-5 ohms when measured at 20°C (68°F). The transmission pressure control solenoid is an electronic pressure regulator that controls pressure based on the current flow through its coil winding. The magnetic field produced by the coil moves the solenoid's internal valve which varies pressure to the pressure regulator valve.
The Powertrain Control Module (PCM) controls the pressure control solenoid by commanding current between 0.1 and 1.1 amps. This changes the duty cycle of the solenoid, which can range between 5 percent and 95 percent (typically less than 60 percent). 1.1 amps corresponds to minimum line pressure, and 0.1 amps corresponds to maximum line pressure (if the solenoid loses power, the transmission defaults to maximum line pressure).
The PCM commands the line pressure values, using inputs such as the throttle position sensor.
The pressure control solenoid takes the place of the throttle valve or the vacuum modulator that was used on the past model transmissions. If the duty cycle drops below 5 percent or rises above 95 percent, DTC P0748 will set.






TORQUE CONVERTER CLUTCH SOLENOID VALVE

IMPORTANT: The Torque Converter Clutch (TCC) solenoid resistance should be 21-26 ohms minimum when measured at 20°C (68°F).

If a fault is detected in the TCC solenoid circuit, code P0740 will set.
The torque converter clutch solenoid valve is a normally open exhaust valve that is used to control torque converter clutch apply and release. When grounded (energized) by the Powertrain Control Module (PCM), the TCC solenoid valve stops converter signal oil from exhausting. This causes converter signal oil pressure to increase and shifts the TCC solenoid valve into the apply position.
The brake switch is an input to the PCM, and the PCM directly controls the TCC apply based on the brake switch status.






TORQUE CONVERTER CLUTCH PWM SOLENOID VALVE

IMPORTANT: Torque Converter Clutch (TCC) PWM solenoid valve resistance should be 10-11 ohms when measured at 20°C (68°F), and 13-15 ohms when measured at 100°C (212°F).

The torque converter clutch PWM solenoid valve controls the fluid acting on the converter clutch valve, which then controls the TCC apply and release. This solenoid is attached to the control valve body assembly within the transmission. The TCC PWM solenoid valve provides smooth engagement of the torque converter clutch by operating on a negative duty cycle a variable percent of ON time.
If a fault is detected in the TCC PWM circuit, code P1860 will set.