Hey all. I have an odd issue. 2006 4.4 HSE, just had the gearbox replaced. Gearbox shifts fine but now it throws code P0929. Which refers to the shift interlock solenoid. Which is stuck in the open/unlocked position. So the shifter can be moved without brake or anything. When this happens the transmission goes into safe/limp mode and only stays in third. If you clear the code it shifts normally until the next restart. I checked the voltage at the shift lock solenoid and both wires are at a little below 3v… stepping on the brake changes nothing and neither wires have ground. The motor / solenoid itself will move when 12v is applied but its default position is retracted without voltage.

Also while in the shop apparently the steering column ecu failed. So now I must pull fuse 18 every time to start the truck until I can replace the steering column assembly.

Think these failures are related?

Battery is about a year old and is a Champion AGM, alternator was replaced right before truck went in for the new gearbox. Battery is fully charged.

I’m going to start by replacing the shifter assembly since the solenoid is clearly not functioning as normal defaulting to unlocked with the plunger in. But the odd voltage and lack of ground to the solenoid gives me pause as well. Is the computer just not sending voltage there since it sensed and open circuit from the faulty solenoid?

And is the P0929 code from the solenoid causing the limp mode? I have no other codes and when that one is cleared the trans fault goes away.

Thanks!!!