
IMPORTANT: Always refer to the factory wiring diagram for the vehicle you’re working on to avoid wire color and terminal number discrepancies. If voltages fall outside of these parameters, it indicates a wiring issue or a faulty sensor and the TCM will set DTC P0934 or P0935. The line pressure sensor voltage signal should always be between 0.35 and 4.75 volts. As line pressure increases, so will the signal voltage. When line pressure is low, the line pressure sensor signal voltage will also be low. It provides a line pressure sensor signal to the TCM that varies in voltage based on line pressure. The line pressure sensor receives a 5-volt reference signal from the TCM and a sensor ground.

Now let’s look at the pressure sensor (figure 2). When duty cycle is low, less pressure reaches the pressure regulator valve through the pressure solenoid, increasing line pressure. This means that, when commanded duty cycle is high, more pressure reaches the pressure regulator valve through the pressure solenoid, reducing line pressure. There’s no oil at the spring side of the pressure regulator valve. The line pressure solenoid directs oil to the end land of the pressure regulator valve. Let’s take a closer look at line pressure control by examining a partial hydraulic diagram (figure 1). The line pressure sensor creates a signal based on the transmission line pressure, which the TCM uses to monitor that pressure.

When duty cycle is at its highest range (65% or solenoid on) pressure drops to minimum. When duty cycle is at its lowest range (5% or solenoid off) pressure rises to maximum. The TCM controls the variable force solenoid by increasing or decreasing the duty cycle to obtain the pressure necessary. The line pressure solenoid is a variable force-type solenoid and is an integral part of the solenoid pack. The TCM uses the line pressure solenoid and the line pressure sensor to control pressure in this transmission. Let’s start by examining how the pressure control solenoid affects pressure on this transmission:
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We’ll look at how they control pressure through the pressure control solenoid, and discuss some common issues and how to troubleshoot line pressure related DTCs. This month we will be looking at pressure troubles of a different kind the sort related to Dodge and Jeep vehicles with the RFE family of transmissions. If you’ve been in the transmission repair business for more than a month, you’re probably quite familiar with these scenarios and the pressure they bring with them. Or maybe it’s Friday afternoon and customers are “patiently” waiting to get their cars back so they can go out of town for the holiday weekend. It’s Monday morning and you already know it’s going to be one of those days, because the shop is busy, cars are everywhere, and the phone is ringing off the hook. Covers the trouble codes associated with these systems and the basic diagnostic steps for isolating problems.

A look at the pressure control system on Chrysler’s RFE transmissions, with an in-depth view of the solenoids they use.
