P0785 Shift Solenoid

[Jeff Davis]

My 98 1500 started shifting really hard into second on real hot days. Then got to where it shifted hard after a few miles, even if it wasn't hot out. The last couple of times I drove it, it was real hard to get going from a stop- like I was pulling too heavy a load or spinning on ice or something, and would not shift out of third. The last trip in it I got the SES light and it read P0785- shift solenoid. I dropped the pan, changed fluid and filter and both solenoids. Put 'er all back together, erased the codes and took it for a test run. Ran like a new one for about 2-1/2 miles. I stopped to make a corner and the hard shift into second happened, and the slippery start from first happened at the next corner. That popped the SES light on again. P0785 again! WASSUPWITAT??

 

[Black_cirrus]

Did you check the harness in the pan for chaffing or damage? I'd check wiring, since you just filled it maybe you can ohm the sensor from the connector on the side of the transmission.

 

[Jeff Davis]

I didn't. I'm not too handy with a meter...
I do know how to ohm the sensor when it's exposed, though.
??

 

[Jeff Davis]

One thing I noticed: (Sorry, this is the best way I know to describe this)
In each hole where the solenoids go, there is a black (feels like plastic) little "piston"- I assume that is the valve?
The one toward the passenger side moved freely in the hole. I could push it with my finger and fluid would drip out of the slots. The other one felt like it had pressure on it, almost pushing it out of the hole- like it was spring loaded or something. With the solenoid out, it would stick out about a quarter inch or so. I could push it in and it would pop right back out. If that even makes sense.
Is that normal??

 

[Jeff Davis]

And to clarify my original post above, the slow take off is like I'm in too tall a gear, like 2nd or 3rd. It's not "slipping". And I don't think it ever shifted once I got rolling. Is that "limp home"? If so, that's more likely an electrical issue, right?

 

[rhino]

Which solenoids did you replace? The back two shift solenoids? Code PO785 is for the 3/2 Downshift Solenoid. It is in the front. If you put the right solenoid in, for sure ohm the wire from the PCM to the Transmission. If you need a wire diagram let me know.

 

[Jeff Davis]

Which solenoids did you replace? The back two shift solenoids? Code PO785 is for the 3/2 Downshift Solenoid. It is in the front. If you put the right solenoid in, for sure ohm the wire from the PCM to the Transmission. If you need a wire diagram let me know.

I replaced both A and B solenoids on the front side.
Diagram would be great. Thanks!

 

[woody60]

Did you ever get it fixed?

 

[Jeff Davis]

Did you ever get it fixed?

As a matter of fact, I just drove it home from the mechanic's place two days ago.
I had a couple of bad ground wires that were causing some voltage issues. (originally thought it was an alternator problem) Fixed those and found a burnt connector on the 3-2 control solenoid. Replaced solenoid and got the wiring issues fixed and it is working perfectly!