Hello to all I recently swapped my transmission for an junkyard one, I have a 2004 g35 coupe rear wheel drive and my car goes into limp mode now for reference before my transmission swap my old transmission was slipping in all gears and couldn’t reverse but now with the new junkyard one I can reverse and drive it just goes into limp mode with the a/t check light on and caps me at 3-4 rpm’s tried resetting ecu and unplugging the fuses but no luck any suggestions would help

 

Exactly what codes is it throwing?

 

min getting
p1764
P1754
U1000
C1136

 

Ok so starting with the U1000 means one of the computers is unplugged or not working. If it wasn't throwing that code previously then I'd suspect a bent pin on the transmission harnesses. You have the style with the three harnesses on the transmission right? Two green and one black iirc? And you have the TCM mounted next to your ECM under the glove box yes?

C1136 is the ABS/VDC/TCS computer saying it's missing a major engine control signal.

P1754 - Transmission input clutch solenoid malfunction

P1764 - Transmission direct clutch solenoid malfunction.

You may have a bad transmission valve body. Did you reuse your existing one or did you use the one from the donor car?

I would start by checking the transmission harnesses for a bent pin, and clean up the transmission ground wire on the front of the timing chain cover, top middle. Two wires landed on two bolts, clean them both up. Also clean up the engine to chassis bonding jumper, larger gauge wire on the right/passenger side of the timing chain cover, other end lands on a 2 hole lug below the coolant reservoir. Also clean up all the connections on the battery.