So our van has been acting weird for a while now, it was surging up hills and... We then moved and a mouse got into it and chewed some stuff up so I resoldered everything and had it running for a while but the surging /miss kept getting worse and worse. I started replacing O2 sensors, new plug wires and plugs, new air filter, new TPS sensor. Then it just left stranded on the highway after testing it to work and back now the check engine light and the Gen light and overdrive light all just flash at me. The computer for the check engine light also hasn't worked since the miss/surge got really bad as well. So I figured these are known for the pcm going out and all of those are on circuits in that. So I thought that was the issue! Well just put a new one in, and that isn't the issue so I am now at a loss of words... Please help!!!!

 

Does the check engine lite test when you first turn the key on?

Year, weight rating of van? Engine?

 

No, it doesn't work then. It instantly starts flashing everything when you turn the key on. B2500 1996 5.2L

 

Gotta be tryin' ta tell ya somethin', but, what, I don't now. A second PCM did the same thing??

 

Correct the new pcm did the exact same thing

 

Sounds like you missed something.

 

when I was at the dealership, rat nests in vehicle=new wiring harnesses - SOP

it is that difficult to figure out sometimes

 

So I went through the van pretty closely today. Found that the o2 sensor wires had basically deteriorated and were touching each other and shorting out. So all the lights are no longer flashing but the van will still not start, the check engine light is still on but is saying high temp sensor reading and TBS and a couple other sensors. I will be putting the old pcm in to see if that could be the issue. BUT I put it in 1st gear and drive to see if over riding the starter would make it go forward and put in reverse to see if it would go backwards while cranking the starter. And it wasn't engaging, is this controlled by the pcm or is it manual?

 

Was able to finally get back into it today. Fixed the o2 sensor wires and went through all the old wiring and everything looks good didn't start tearing into any wiring harness that wasn't open yet. What's going on now is there are codes for high voltage for throttle positioning, ambient temperature, coolant temp sensor and one other sensor. The weird part is all the wiring looks great from the pcm to where these break off from the harness. It also still has the o/d light on and won't start. I hit the switch I have to override the starter and it still won't fire. I also discovered that I am pretty sure when I was stranded on the highway I believe I could put it in drive and hit the starter override and go forward... Not now it doesn't engage in moving. Could there now be something wrong from being towed as for the o/d light? They just lifted the back wheels so I would see anything bad there. Or could the short from the o2 sensors have fried both PCM's? I tested it with both today with the same results.

 

If you have a bunch of sensors getting too much voltage, that is gonna really confuse the PCM, and it won't be able to run the engine..... Check at one of the sensors, I believe they are all fed from the same source..... should see 5 volts, if it is closer to 12, then there is a short somewhere, or the PCM is bad.