My daughters 2004 3.0 XType has a transmission fault, and is showing code P0778. I can clear the code, and the car shifts extremely hard, and after the transmission warms up, will throw the code and go to limp.

I had to recently replace the TCU so my thoughts went straight to that. I removed the TCU and it was dry without any corrosion.

Using this thread as a reference I removed the connector from the transmission pan and ohm'd the following pins:

18-13: 18.5
18-14: 18.5
18-15: 3.7
18-16: 1 (open)

So it sounds like the 2-4 brake duty timing solenoid is bad and needs replacement. Before I take the transmission pan off, what do you think?

Second:
To remove the solenoid, it seem like all I need to do is drain the fluid, remove the pan, remove the 2 screws holding the solenoid in, remove the wire and replace reversing.

Is there any preference on the brand of solenoid? I was just planning on getting a $40 solenoid off of eBay.

I'm not interested in flushing all the transmission fluid, but I will replace what comes out. Which fluid should I use to replace?

 

nylyon, I would agree with your assessment. Having helped a few other members with this same sort of problem, you will also want to keep an open mind and hand over had the wiring between pin 16 and the solenoid. Your problem may be nothing more than a broken wire and the solenoid is just fine. Granted, I would have a solenoid on hand just in case the wiring is fine and you have it open.

As for brand, can't help you there. I was fortunate enough that I never had to do that repair. Hopefully one of the other members will chime in with their experiences.

 

Thank you. On the outside I inspected best I could, I couldn't find any evidence of wiring issues. Before I remove the solenoid, I'll ohm it at the source, that should be revealing.