Dreaded 'no bus'

[andrewnp]

Okay everyone, this thing has been kicking my butt for a while and I will finally stop being stubborn and ask for help.

I had spurious 'no bus' and p1964 code pop for a while, but the jeep would continue driving fine. 

So one day I was driving to work and my jeep just up and died on me about 5minutes into my way to work.  Read 'no bus' on the odometer.  I got a buddy to tow me up to a spare lot in nearby base housing to keep her safe for a while. 

She has sat there since, and I researched, and recently started troubleshooting.
At first I jumped to the CPS sensor, took some resistances.  They were a little off what they should have been so I decided to swap it with a BWD sensor from AAP.

I come back a few days later and find my radio torn out, my tow strap gone, and rear passenger window punched in(the smaller section behind the window, the actual window was blown out and I have a piece of plywood blocking the window to prevent someone from getting in).

After some rough knuckle hits replacing it, as soon as I plugged in the harness the fuel pump clicked on. She started up, had to reteach it how to idle (understandable due to it being off for so long) and drove it around the lot for a little bit to wake it back up. 

Because I did the Durango alternator swap recently I decided to upgrade the battery cables to 4awg.  After replacing the cables it wouldn't start up.   Crank but no start.  Hopped out and jiggled the CPS harness, and she managed to start for a few seconds before dying again. 

Honestly somewhere( almost positive it was after the battery cables were changed) two of the wires for the radio were tapped together, and I believe shorted something. 

Right now this is where I am at:
Instrument cluster self test passed (and connectors greased)
No gauges read, gas light does come on.
CEL
Airbag light
No bus was on odometer, now doesn't read at all(just happened today, still said no bus after battery cables and worked for self test)
CPS resistances are good
No fuel pressure at the rail
All resistance checks were good on cables, and good after installed
Crank no start

I don't know where to go from here...
-I know the fuel pump has not kicked on since the last time the truck started, but I think that was just due to the truck using the last bit of fuel to fire up.
-ECU problem?
-Bad ground I missed?
-Higher rated alternator, giving an overvoltage on a sensor to the ECU?
-Just another had sensor?


Thank you everyone for any help I get, this is driving me nuts!

[Mr Rock]

Don't you love a good electrical problem!!!!!

It sounds like a computer communication problem, i would go through the connectors from the computer and check them for tightnest and for any possible corrision. one bad connection and nothing will work. I read somewhere that there is a connector just above the gas petal that goes to the TCM that also caused a problem with comunication.

[Bill3753]

What is the year and model (just making sure).  Different years are known for having different electrical issues within the engine harness.

With what you said so far, I agree with Rock in that it sounds like an ECU.  Also, do the stupid checks to be sure the lack of fuel pressure is not from a clogged fuel filter.  I highly doubt that would be the problem as I've never seen one so clogged that NOTHING would get through, however I always start at the fuel filter when trouble shooting a problem in the fuel system as it is normally the most neglected maintenance item on a vehicle.

From there, start by checking all the terminals in the underhood relay/fuse box to ground.  Make sure you don't have something bleeding over to ground.  If your good there, check all the fuses in that same block with a multimeter.  Don't just look at them, use a meter.  I chased an electrical problem in my old ZJ for a week once before and it was all because a fuse was blown but you couldn't see it.  The only way I found it was with a meter.  If all that checks, then check resistance across your ground wire and new power wires.  It will have some resistance on the cable, but if it is very high then you have a problem.

That will get you started and might help narrow the problem down.

[skibum]

Not shure what type of jeep you own but many of them with the plastic tanks are known for fuel pump issues. Wile someone is cranking it over kick the gas tank & if it starts then it needs a fuel pump. Can't even count how many times I have come across this. Also there was many issues with the fuel sending unit reading 1/4 tank when it's actually empty. Very commin in the ZJ's & have seen it in 97 & up XJ's & TJ's.
Your "no bus" issue is not the cause of the no start. Your cluster has lost it's bus signal(the main comunication conection that all the controlers use to comunicate with each other). Again need to no what type of jeep you got so I can try to help you.

[andrewnp]

Thanks for the few ideas guys, will run by with a flashlight and multimeter, make sure the connections are all good.  I did notice that one barrel looking connector directly above the gas pedal was pretty warm to the touch, not sure what it is.

2001 Cherokee classic automatic 4.0L