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The VLPS

Wednesday, October 21, 2015 - 07:00
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Chrysler introduced a Variable Line Pressure Solenoid to the existing 41TE (A604) and 42RLE transmission as early as 2007. The addition of this solenoid includes the use of a transducer to verify line pressure control as feed back to the computer. 41TES and 42RLE-VLP are the new designations for the units equipped with the added solenoid and transducer.

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Its purpose is simple, to improve fuel economy. Typically, factory predetermined line pressures in drive runs approximately 120-130 psi while reverse is usually in the range of 180-190 psi. The shift solenoids double as clutch pressure control solenoids controlling the rate in which a clutch is applied during both a garage shifts into gear and shifting from one gear to the next. Once into gear, the full predetermined line pressure is applied to the clutch. This means that at idle in drive or reverse, the engine is driving the pump through the torque converter at 120 or 180 psi. Lowering line pressure under these conditions causes the engine to not work as hard increasing fuel economy.

This is what the added line pressure control solenoid does, it lowers line pressure when it duty cycles. Characteristically, line pressure solenoids are normally applied solenoids controlling line pressure on the spring side of the pressure regulator valve. The regulated pressure this type of solenoid generally produces runs from 0 psi at 1 amp to 90 psi at 0.1 amps. The added pressure to the spring side of the pressure regulator valve is what raises line pressure. The design of the solenoid is that should it turn off, maximum line pressure will result as a failsafe strategy.

The 41TES/42RLE-VLP line pressure solenoid works entirely different. This is a normally vented solenoid. The regulated pressure this solenoid produces generally runs from 90 psi at 1 amp to 0 psi at 0.1 amps. This regulated pressure works the end of the pressure regulator valve opposite the spring. As it is energized it lowers pressure. As it turns off it restores pressure back to predetermined levels (higher pressure).

The operation of the solenoid is important to understand when it comes to diagnosing problems related to the solenoid and/or transducer.

There are six main codes assigned to this system. They are:

P0868: Line pressure low

P0869: Line pressure high

P0932: Line pressure sensor circuit

P0934: Line pressure sensor circuit low

P0945: Line pressure sensor circuit high

P1745: Transmission line pressure too high for too long

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