Remove solenoid A located on the valve body furthest away from the pressure control solenoid. Remove the valve under the solenoid, and check to see if the spring that is "supposed" to be there is actually present. If not, this may be your problem. When the PCM commands 2nd gear, solenoid A is shut off. This should allow passage of fluid to 2nd fluid circuit to force trans to upshift to 2nd from first. If the spring is missing there's no fail-safe position for that valve to move... simply put, no default action for the valve which should normally be pushed towards the solenoid by a spring to change fluid flow depending on valve position (which is adjusted depending on whether or not solenoid A is activated). Confused yet?

If that problem occured AFTER you had it rebuilt, I'd look to see if the spring is missing or just bound against an opening in the valve body. Make sure that valve can slide in and out by momentarily pressing on the valve then releasing (with solenoid A removed, of course). Oh yeah... in order to do that, you'll have to drop the pan (as if you didn't know that by now, huh?).

 

Assuming no one has disabled the DTC reporting for transmission components, disconnected plug would throw quite a few codes. I've had that happen TWICE.

*edit*

And they'd have figured that when they checked the tune.... ASSUMING they didn't disable any trans codes.

 

If I read this thread correctly this problem has been with two different transmissions. With that being said in order to have 1st gear and 4th there is an issue with the A solenoid working properly. I do not feel because there have been two transmissions and computers that the problem is with the trans or the ecm. I would suspect that the harness plug has a pin that has been pulled out not making a proper connection. I would look closely at the plug and also look the wiring from the computer to the transmission. Also if any code tests have been disabled turn them all back on for diagnosis purposes. Vince

 

Word, since you've already swapped trans's and ecm's, you've basically narrowed it down to a harness problem...

 

Maybe I read the post wrong (doubt it ), but I don't think a different trans was swapped in. Based on original post (below)...

...it functioned in 1st gear, but slipped when attempting to shift into 2nd. With that said, solenoids were suspected of being problematic. That didn't resolve the issue, so the trans was dropped & rebuilt (replacing internals). Bolted trans back up & now it won't start in 1st (subsequently, no 4th either).

Now... big question is... are ANY DTCs disabled? Only gold can answer. If NOT, then I wouldn't be willing to bet 100% it's a wiring issue. If codes are disabled, then (like you said) re-enable, and see what pops up. Question I have now... after reading first post again... is during the SECOND rebuild attempt, did you check the movement of the shift valve under solenoid A? One would think a problematic solenoid or open loop would set a DTC.

 

It was working great then it started acting up, the owner rebuilt it and did the same thing. Then tried a different tranny and still did the same thing. The pins are ok and there are no tranny codes. Could the vcm have anything to do with it?

 

I stand corrected....

 

Take everything you've been told (history) and toss it out, focus on symptoms here and now. If the one trans doesn't roll in first unless it's in manual first and has no overdrive it has to be related to the Solenoid "A" circuit as Vince pointed out. There are no single mechanical failures that would produce that exact pair of problems that I know of.
The reason it moves in manual first, but not "O" or "D" first is because the forward clutch pack is not getting apply fluid for first gear. The low/reverse clutch pack activates in manual first and is enough to move forward - but there's no torque holding ability to it so don't gas it in manual first or you'll smoke it and won't be able to back up anymore! In second and third the Solenoid "B" circuit is feeding the forward clutch apply circuit but re-applying the band for fourth gear requires the Solenoid "A" circuit which isn't working.

 

So how about excessive resistance in the circuit to Solenoid "A"? There may be enough of a connection that it doesn't toss a code, but have enough resistance that it doesn't activate the solenoid. Sounds like a wiring schematic is in order.