I had a tree jump out in front of me a couple months ago and it didn't move. My right front headlight pretty much got pushed all the way to the firewall. Looking at the truck I thought it wasa done deal. But winter was coming and buying a different truck wasn't in my budget so I headed to pick n pull. Surprisingly I got the truck back together for $400. But I have some issues. Alternator not charging. So to get by I got an external voltage regulator to charge the battery. The main problem is my transmission. It's in limp mode. I only have 2nd and 3rd gear and i have to manually shift. The transmission relay is not switching. I've checked continuity between the pcm plugs and the relay and alternator. Their good. But im thinking the pcm may have gotten jarred and broken some solder points off the board. I guess before I commit to another pcm I thought I'd see if anybody had any suggestions.

My faults

 

Are you getting power to the trans relay?

 

yea. On the load side of the relay (30) is battery voltage, but the signal wire that should come from the ECM it does not give voltage. Im unsure if the ecm provides the ground signal or a 12v signal tho. Im thinking it's 12v. I removed the ecm and cover and it's filled with this ballistic gel crap that just makes checking the components pretty much not worth the effort. Everything is pointing to the ecm but with the protective gel that it's surrounded in it really makes me wonder how components could shake loose or lift off the board. Although I have seen a guy on YouTube that extremely savvy on ecm's and he does mention that it does happen

 

If the fender went all the way to the firewall, the entire ecm harness is in that general area... I'd carefully check all the wires, with a test lamp - if you're using a digital volt ohm meter, they tend to use so little current that it'll show a damaged wire with only a couple connected strands as continuous. I've been fooled before, and now use a test lamp that draws some current. I have a 2000 2500 in the user classifieds, if you find you need something. Good luck!

 

PCM controls the ground side of the circuit to engage relays.

 

thank u. Yea I'll prove the connector directly out the pcm with a test light and see. Which would mean I should connect the clip to positive and touch the control with test light to see if ground is switched, right?

 

I'd probably leave it all connected, clip to positive then pierce the wire close to the pcm with the sharp end of the test light and see if it lights up. If the lamp lights, move close to the trans side of the connector and do the same. If that lights up too, thinking maybe the trans is hosed up.

If the first test doesn't light up, could be a different wire failure that is causing the logic in the pcm to not do the right thing - or the pcm itself is hosed up like you're thinking And in that case, might be quicker to just swap out another pcm and see if those problems disappear. If you swap and retain the problem,then you gotta just start testing that whole harness - which would be pretty time consuming. Or swap out the entire harness, which isn't all that quick either... but it'd give you a chance to clean up all your contacts.

I have a fluke automotive meter that was probably $400 new... But I find I use the 20 year old $6 test lamp more often for this kind of stuff.

Good luck!

 

so I probed the signal wire for the relay and it lit right up. Checked the socket that the relay plugs into and it lit right up. Plugged the relay back in and cleared all the codes and it fired up with only one code for EVAP which is expected and not an issue I'm worried about right now. Took it for a drive and not only does it shift fine again, but the alternator is once again charging. I have no idea what was wrong or what fixed it. I've had those 3 plugs out of the ecm numerous times. Lol. Im not complaining. I think it knew i was on the right track and decided to get right...