I have a 1998 Dodge Ram 1500 5.9 V8 that won't shift up into 4/OD. I have dropped the transmission pan and changed solenoid and sensors that seem to cause the usual problems. However, despite doing so it is still giving me the check engine light and saying it won't shift to 4/OD. I'm hoping maybe someone can help me with some possible solutions to my problem before I decide to rebuild the transmission. I will also add that it shifts 1st 2nd and 3rd like a champ with no problems whatsoever. But I would like the piece of mind that comes with having a fully functioning transmission. It also will shift into 4low but not 4high.

 

The PCM controls the O/D solenoid by grounding the circuit. Probably a break in the wire, or a bad connection at the trans, or PCM.

 

What is the best way to check if it’s a faulty PCM?

 

PCM is requesting O/D, not getting it, and setting a code. So, the PCM is at least TRYING to do what it should. Check the wire for the O/D solenoid control circuit. If the wire is good, likely a bad PCM.

 

I’ll try and check the wiring. I’ve been told I have to put in a new transmission but if I can just buy a new PCM that would be a lot better for me, thanks!

 

You can test the trans by running a wire from the trans (splice into the ground side of the O/D solenoid), to a switch, that you can ground anywhere in the cab..... go for a drive, and at 45-50 mph, flip the switch. If the trans shifts into O/D, it's a wiring or pcm issue.

 

I don’t know if this info help diagnose my problem but when I’m driving around and push the O/D button on and off there is a short spike it RPMs like it’s trying to something but I’m not sure what that’s telling me.

 

If it is only like 200RPM, that is TCC unlocking/locking.

 

Yeah that’s all it jumps. And it’s only when I push the button and it’s not doing it all on its own.

 

That part is working as it should then. Need to check that wire.

Brown wire, pin 6 at the trans, Connector 2, pin 21 at the PCM.