Last week my Gryphon threw codes for my TCC Solenoid. Since it was time for a fluid change anyway I proceeded to change the TCC and wiring harness. Refilled with fluid started truck and within a minute truck started running rough and the code for the EPC Solenoid Open Circuit (P1746) was thrown. I thought maybe I had not gotten the wiring harness secure so I went back in and made sure of the connection. Buttoned everything up, refilled, fired her up....same thing.

Needless to say after having the pan down twice, using ample amounts of fluid, I'm sort of aggravated :0) but not deterred. Has this happened to anyone else? If so why would the EPC code not have been thrown when the TCC code was? Could this be a defective harness or do I need to swallow hard and go back in to replace the EPC? Thanks

It's a 2002 F150 Screw w/ 5.4L and 165k miles (4R70W)

 

A multi meter can tell you if it is a defective harness or a bad solenoid. Unfortunately the pan has to be off to do that.

 

I'm all about learning here so feel free to take me to school. My understanding is that I can check the EPC solenoid and other transmission electrical issues without dropping the pan via the wiring harness. Now that's after doing some technical reading which gets confusing. Is this really doable and if so how do you do it?

I knew the TCC solenoid was bad and replaced it but I don't want to just start throwing parts at it nor do I want to replace the EPC only to have another electrical issue arise. Just want to do the job right. Thanks

 

You can check it with the pan on. Remove the trans connector from the side of the trans. You can probe the pins to check each solenoid. I don't have a diagram to show which pin is which. The hard part is seeing the pins. A mirror might help.

 

Mark, thanks for the info. Very helpful!!!

 

Guys, im living proof God has a sense of humor. In testing my solenoids the TCC & EPC both looked bad but it wasn't the solenoids but my multimeter. Now that I've got a good multimeter the TCC & EPC both test good, however, I replaced the TCC and still getting P1746 code. I'm not seeing any wires being burnt through but not sure what to do now. All fuses are good. Where do I go from here?

 

Please see above update. I'm needing some help if anyone has some ideas. Thanks

 

You check the wires between the PCM and the trans connector for continuity, short to ground, and short to power.

 

BINGO!!!! The new wiring harness I purchased from FORD was bad. All that work and a new part was the problem. Good grief. Mark, thanks so much for the help!!!