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no bus. Can someone explain this?

7K views 8 replies 6 participants last post by  RogerRamJet 
#1 · (Edited)
One day I start the truck and I have no gauges working. I go for a drive and it runs good and there is no tachometer or speedometer. Where the odometer is there are no numbers but it says no bus. No fuses are blown. The overhead info. display only shows ccd.
2000 MY, 2500 SLT Lariat, four door, long bed, RWD, 360 cu. in. gasoline motor, auto. trans., 85,000 miles. The engine icon and the abs and the airbag lights are on in the instrument cluster. Today I had a diagnostic check done and there are no codes thrown. Help will be appreciated. CB
 
#2 · (Edited)
It sounds to me like the solder connections on the back of the speedometer are cracked, and no info is travelling up the spinal cord to the brain, so to speak.

Here's a thread where a member didn't care to listen for a few days and then finally did. I'm not 100% sure it's your problem, but I have seen it before on these trucks.

http://www.ramforumz.com/showthread.php?t=141037

Pull the speedo and check the connections.

Some Rams experience this as well as the older Caravans, Voyagers, Mitsubishi, Eagles etc..

No Bus=No communication. It may just as well say "Duh" and be drooling on itself. Stupid term but hey, that's what it is. Bus is the term used between the computers on your truck. No bus, no communication. It could be a fuse but I doubt it. You'd have found that long ago. Your PCM is unable to communicate and a severed spinal column is a good reason for the brain (Speedo cluster) won't do what it's told. Try wiggling the face of the cluster and see what it does, it might make a connection.


Is that an acceptable explanation?
 
#5 ·
Either one of the modules on the bus is defective (like the cluster itself) or the connections between them is loose or there is some corrosion. The thing about the data bus on these vehicles (aka the CAN Bus) is that there is no type of error checking, essentially it is send and pray between modules. So everything electrical between them needs to be perfect.
 
#7 · (Edited)
I had the same problem about 4 years ago. Lost all guages for about 3 months. Got one ticket and got out of it when I showed the cop. I wish I could tell you what I did to fix it but the dang thing fixed itself... until now.

From my research, the no bus signal means a networking problem between the computers. This means that any sensor in the loop, frayed wiring or the actual computers themselves could be the culprits. Unfortunately, there are a shiton of them that are all looped in.

You can check the dashboard connections but before doing that, I'd suggest checking the wiring plugs going to the PCM on the left passenger side on the firewall and the plug going into the ecm behind the battery driver's side (take the cover off and look for the plug with the screw in the center) and the BCM located on the left behind the parking brake. Remove neg batt cable then remove the connectors. Make sure there is no broken wires or corrosion (usually green)on the pins. If there is, clean them. Use some dielectrical grease and plug them back in. Turn the key to the on position for 10 seconds or so with the neg. cable still removed(i'm told this resets the PCM). Return the neg. cable and see what happens.

If that doesn't fix it, I'd pull the guage cluster to check connection or begin testing the sensors for a short. I'm told the camshaft sensor is one of the most common failure points. Try that first. What sucks is even a short in a completely unrelated area (such as the radio wiring) could cause a No Bus signal.

Good luck.
 
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