I've been struggling with the "no bus" issue for nearly a year. My Ram is a "nonessential" vehicle (I'm a telecommuter, and we drive my wife's car most of the time otherwise), so I haven't really focused on it, but after having three stalls (one of them for 30+ minutes) last weekend I decided I HAVE to get this fixed.

I have all of the classic symptoms listed in other threads. It will be running fine when engine cuts out suddenly. Cycling ignition to restart makes gas gauge go to zero, after a 10-15 secs get "no bus" on the odometer (920-921-999 on self-test). Cranks fine but no spark. After anywhere from immediately to 30+ minutes later gas gauge will come back and I can hear fuel pump come on, it'll start up again and run fine for another random amount of time. Stalls are inconsistent-- not due to acceleration, braking, turning, anything I can identify. Seems to be more frequent when the engine or weather is hot, but then again more than once after stalling early it's run fine for an hour.

I've replaced the crankshaft position sensor, camshaft position sensor, and PCM (swapped for remanufactured unit). Any recommendations on where to head from here?

Since this a no bus issue and appears to affect the ASD system, I'm wondering if there's a floating or shorting ground issue somewhere-- haven't ever touched the electrical system so I'd have some learning to do. While I was waiting for it to revive last time, I did notice that there's a set of three body grounds in the center of the engine compartment, and one of them was hanging free. It was very short, maybe 12", so I assume that belonged either on the engine or the PCM-- any pointers on where it should go? I have the 2001 manual PDF but couldn't find it.

One last tidbit, around the same time I started getting the stalling problem, two other systems stopped working (and haven't worked since): the radio (completely dead) and the a/c. Again, could be a total coincidence, but it could also be a place to start troubleshooting.

Appreciate any pointers or direction. From the other threads, it sounds like 99% fixed their problem with one of the three parts I've already swapped. Lucky me....

Thanks,
Matt

 

Yet another issue that has been covered ad nauseum.

 

Huh? If you read my post you'd see that not only have I read all of the other posts (repeatedly over the course of the last year), but I've tried and exhausted all of the solutions in them.

But hey, any chance to use your snarky animated GIF right?

Matt

 

Does your horn work? If it does, swap the horn relay, with the ASD relay, and see if the problem goes away. If it doesn't, check the fuse... There was another member some time back that his a/c wouldn't work, but, after he changed the horn fuse, it started working again......

 

Yep, that was one that had me hopeful back when he posted it, but I tried it and no joy. I should also have put a few of the other little things I read in other threads and tried w/o success: tightened inline connector, wiggled every bundle I could reach to try to trigger a stall (or recover while nobussed), replaced battery clamps, tested battery (85% life remaining), pushed on PCM connectors (this actually worked to recover from a stall prior to the new PCM).

What else could I be missing? Any idea where that dangling ground is supposed to land? Or even a good reference to where I can find it myself in the 2001 manual? There was a thread that speculated that grounds were particularly important, so that's my latest tack on this...

Thanks again,
Matt

 

Look in section 8W "connector/ground locations" for a list. There are even pics further into the section, to show where they are. Might be able to identify yours by the pic. (they are grouped reasonably well in the pics....)

No joy on diagnosis for no bus in the service manual. Seems there is a second book that would be good to have.... the "diagnosis" manual. (or some such.)

What you are getting though looks for all the world like an ASD event. (indicated by no spark when cranking.) You have already replaced all the usual suspects for that though... so, I am thinking a wiring problem somewhere. Re-check your PCM connectors, make sure they are all nice and clean, and tight. I would follow the wires for the crank/cam sensors as well, and see if they aren't pinched somewhere.

 

Another thread was not needed to confuse things. But hey, that seems to be the norm now.


Anyway, take a pic of the hanging 12" ground wire you have hanging.

 

there should be about 3 ground wires to the PS bracket bolt. leaving those loose or off will cause a NO BUS.

 

Stalled out a bit on this (pun intended). Sorry for creating a new thread-- after getting the feedback I really considered tacking my original post on to one of the old threads and letting this one die, but I think my issue is going to end up being completely different than all of them so at the risk of alienating some I'm going to keep this one alive. I will definitely tack on any future issues to old/relevant threads....

A photo of the loose wire is attached. I under-estimated, it's exactly 18" long. There are two others which disappear between the engine and the firewall.

I checked the PS pump and the only ground I see is the massive one that connects directly to the battery neg terminal.

Additional troubleshooting steps since I last posted: I've had a problem with the battery dying on me. I only drive this truck on weekends (it's more of a hauler than anything else), and lately it's been dying if I leave it sit for more than two weeks. I checked current draw (no key in the ignition, all lights off) and I'm seeing 0.2A-- is this normal?

I disconnected the battery, put it on a charger, and it charges to around 12.3V. After taking it off charge, it drops to 12V after a few hours, down to 11.9V after a week but steady after that. It's a POS Wal-Mart brand and four years old, but AZ tested it months ago said it had plenty of life. Any chance it's the culprit? Worth changing out even if it tests fine (thinking it could test fine cold, but have probs hot)?

I also tested voltage with the engine running, 13.60V or so at idle (a little high since the computer has been disconnected for two weeks) and 13.80V or so at 2k RPM.

Two random other facts, maybe related. I don't think either should affect the ASD system, but...

• A/C is not cooling. I don't care, I don't use it. Any chance one of those sensors is borking the bus? I think I hear a clutch engaging very occasionally, but I haven't tracked it down. Should I be pulling fuses or connectors if I want to just leave the A/C dead?
• Radio is also dead. Never bothered to diagnose (like I said, it's a hauler). Worth investigating?

Thanks again,
Matt

 

Your pic is, I think, a ground wire that should go to the back of the head.

There should be a couple more grounds up by the power steering pump, coming off the main harness for the injectors, and such. If those aren't there, I would start looking for where they went.