I have read so many threads about NO BUS error... now it is my turn.

2001 2500 5.2 set up to tow...

3500 miles into a winter getaway started early January. Do laundry on SUnday afternoon driving there from campground in FL. 1 hour later... NO START...
Cranks good... no problem I think cause I brought spare coil, optical dist sensor, and crankshaft postion sensor... through those in with no luck.

Monday tow to Dodge dealer in Chiefland FL... young mechanic dude shows me No Bus indication on speedometer... I cry...

He works on it for 2 hours and gets it running. tells me he plugged and unplugged and wiggled CPU wires and all of a sudden it works. I pay and leave and thank him. Travel 165 miles towing with no problem the next day. Start and go several times over next couple of days. Go for breakfast, van starts but dies, then starts up again. Get a bite to eat. Leave restaaturant, start up pull out and die in parking lot.

Good Samaritan tows me to local garage. They pull and wiggle wires with no results for 1/2 hour... basically telling me either bad CPU or bad harness. Push me out of bay. I continue to dig deeper wiggle igniation switch, wiring harness, battery cables, anything I can think of for another 20 minutes. I step back to think and with key in on position I hear the fuel pump and a click, so I turn key and it starts. turn off, restart several times.

I literally did nothing to make the noise I heard sound off... it just did on it's own. Just like it breaks down... on it's own.

I am at this campsite in FL for another 10 days then have to be off to home another 900 miles away.

I am electrically savvy and know my way around a meter and contact cleaner. I have solder and an iron with me.

I put in a new fuel pump 10,000 miles ago. Complete tuneup within last 30,000, plugs, wires everything. NO codes pop up even at the dealership using his computer reader. He tells me long term mmemory readings all look good. Everything points to intermittant electricla connection.

Any ideas?

1. Ignition switch (wiggled with key in and nothing)?

2. Bad CPU? In my training CPU's don't go intermittant.

Previously have had very little contact with the CPU harness and the van is generally fairly corrosion free. The wires from the harness... well two wires looked like they may have been compromised, cut out the bad 1/2 inch and soldered the ends together... but that did not seem to correct the problem.

3. Does it take minutes for the CPU to fire up after being disconnected?

Can anybody tow my camper from Apalachicola to Cincinnati if I can't figure this out? With my wife and don't need hassle goiig home. Can't afford a new truck...

I drove it home just now from repair shop to camp ground and will dig in when maybe someone can point me in right direction.

Thanks for any help...

Roger

 

No bus error literally means that it cannot communicate with the pcm - unplugged connection or bad pcm - or that the information it is receiving is corrupt or not what it expects - dirty or loose connection, or bad pcm.

In theory any grounded or mashed sensor wire could also cause the pcm to go into an unknown state (where it doesnt understand whats going on and refuses to operate) although my Chrysler documentation states this is not possible. Regardless, its something I'd be looking for if simply disconnecting/reconnnecting the pcm doesnt solve it.

It is a very bad idea to wiggle, unplug or replug the pcm connectors with power applied. Any time you do this you are risking permanent damage to the pcm. The procedure is: disconnect the battery, drain the residual power in the pcm by turning the ignition on for 30 seconds, turn ignition off, then proceed to disconnect/reconnect or wiggle the connectors. When you are done and its all reinstalled, only then should you reconnect the battery and retest/restart.

If you unplug and replug the pcm with power applied, even if you get lucky and dont destroy it, the pcm will certainly go into an unknown and unresponsive state. Wether it can recover on its on, or requires rebooting by disconnecting it as described, is unknown. This could certainly result in it becoming unresponsive and perhaps eventually resetting itself.

A bad ignition switch can certainly keep the van from starting or running. But should not be capable of giving a no bus error by itself.

If unplugging/replugging the pcm as described does not resolve the issue then I think you'll have to replace the pcm.

Sorry you are having to go through this so far from home

 

Thanks blackvan...

I cringed when I saw the local mechanic plugging and unplugging the PCM with the battery cable connected. But this time he got away with it. I think...

As I mentioned, after he gave up (it did start then die twice on him) they pushed it into the parking lot to free up the bay.

I identified two possible wire breaks and cut and resoldered them together. Of course the battery was connected. Then I took off the positive cable and reseated it and clamped it down good as it was a little loose. Maybe that was the reboot... and the wires I fixed were bad?

I then continued to gently work on jiggling the wires, when presto, the noise that you get on startup happened, ( I did have key turned on) minutes after me reconnecting the battery. I turned the key and it started. Turned on and off a couple of times then drove about 15 miles to camp site.

I just added a ground wire from alternator bracket to NEG terminal.

I just started it a couple of more times...

Looking through these recent topics, can a bad ASD relay give this NO BUS indication? Does that not need energized to turn on fuel pump and such?

thanks for the quick response...

 

Dodge mechanic told me that the first of the three connectors was the "BUS" and that the other two connectors were mainly sensor input/outputs.

 

Sounds like it to me. What happens is the solder joints break on the board where the connectors are soldered on. That's why it's intermittent...heat and vibration.

 

thx for the info alloro...

did you or someone else ever try to resolder the board?

I am a super solder guy... had lots of practice running a Heathkit store for 10 years... (Ever hear of Heathkit?)

I have my solder iron, various tips, flux and solder with me. What is it like to open up that CPU container on the firewall? Should I look at it? OR is it too risky while on the road like I am and stranding myself?

I know this has been covered before... but should I order a rebuilt CPU and just replace mine? and from where???

 

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not sure if this helps or not, but I have gotten remaned computers from florida, not sure where, but they were like $100 with exchange, you order it, they send it to you, and you return your old one

you can usually find them on ebay

 

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That's not entirely accurate. PayPal will ship to any address you have registered with them. So as long as he enters a second address in his PayPal account before ordering the PCM, then he can choose which address it goes to. I know this because I bought a printer for my daughter when she was away a college. By using the second address I was able to have it shipped directly to her.