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Bought a rebuilt 4L65E from a high volume online shop for an engine swap project that won't shift into 1st or 4th. I added LED indicators in the cabin, wired right to the harness at the tranny connector, so I can watch what solenoids are being grounded and see it is all normal. I'll drop the pan and replace the A and B solenoids, but without codes being set, I'm expecting it to not be that easy. What can also cause this but not set codes? LQ9, stock ECU from the donor truck, rebuilt 4L65E ordered as a replacement for the donor truck. The rebuilder will stand behind the product and send me a replacement, but having to get this one out (again) is more than frustrating.
Transmission codes can usually only be pulled by a scantool.
I've got a similar issue and I'm stumped. I just pulled my transmission and tore it down and still haven't found any problems. Maybe if you know someone with an ECU you can borrow, that might solve something.
I agree with Jays that the problem is related to Shift Solenoid A; if not the solenoid itself, then something connected to it in the valve body. This assume that the PCM and harness really are grounding solenoid A when commanded. Mechanical problems in 1st gear are extremely rare; when combined with no 4th gear, we can state with 99.9% certainly it is solenoid A or related hydraulic circuits.
Bit the bullet and pulled the (no drain plug) pan. After pulling the drive shaft, in the way of course. Found the problem. I tested the solenoid and it does nothing. Hopefully that is all there is wrong with this. Burnt solenoid
Glad you found the problem. If the solenoid still has electrical continuity the PCM thinks its good (no code), but we had several reports of the internal rod sticking and therefore no longer shifting the trans.
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4L65E no 1st, 4th, and no codes 
