failed EPC solenoid in Trans.

[biggiesize]

While I sit here running things through my mind,Im thinking about all the solenoids in the 5R55E.What im wondering is this:If the EPC,TCC or the other 4 shift solenoids,all of which allow fluid through them goes bad,could it restrict the amount of fluid that is going into each shift solenoid to shift gears?Is there an override to allow fluid to bypass these solenoids to prevent failure of the particular gear that the solenoid controls?If one of these solenoids goes bad will I get a light on the instrument cluster or is the trans not hooked up with warning lights?Maybe Im just misinterpreting hoe these solenoids work.

 

[dogfriend]

If you have a problem that sets a transmission code (DTC) it will flash the O/D light on the instrument panel. There are several codes related to the various solenoids. If you have a failure of the EPC solenoid, you should also get other symptoms because the EPC solenoid controls the line pressure (main hydraulic pressure) in the transmission.

As far as the action of the solenoids goes, the shift solenoids are either on or off; they either block flow or allow flow. The EPC and the TCC solenoid are PWM (pulse width modulated) they are not fully on or off, but are used with a duty cycle where they are on some of the time and off some of the time to control pressure.