No Bus signal

Tiny
19STORMGSI90
  • MEMBER
  • 2007 DODGE MAGNUM
  • 3.5L
  • V6
  • 2WD
  • AUTOMATIC
  • 123,000 MILES
Driving down the road and all gauges and wipers went crazy then car shut off. Battery ended up coming unhooked and now it says no BUS and nothing works. It will start and drive but it is not right. Also the ABS fuse blows every time I put one in. I was told it was the PCM so I bought a new one and it still wont work.
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Sunday, September 18th, 2016 AT 7:03 PM

13 Replies

Tiny
CJ MEDEVAC
  • EXPERT
Maybe recharge the battery to 100%, with one post disconnected.

Then hook the post back on and fire it up.

If you just jumped it off to make it run again, the computer may still be sensing low voltage

The disconnection for a while may reset it, now sensing full voltage

You may have to relearn idle (driving it), the rest may be back to normal.

Regardless, this idea wont hurt anything, even if I am wrong.

Return with good news!

The Medic
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Sunday, September 18th, 2016 AT 7:58 PM
Tiny
CJ MEDEVAC
  • EXPERT
Mis-read your question (tired and its late)

I will message another expert who can help you.

Sorry!

The Medic
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Sunday, September 18th, 2016 AT 8:09 PM
Tiny
19STORMGSI90
  • MEMBER
Okay, I will give it a try thank you.
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Sunday, September 18th, 2016 AT 8:09 PM
Tiny
CJ MEDEVAC
  • EXPERT
Just sent message to another guy to help you!

The Medic
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Sunday, September 18th, 2016 AT 8:12 PM
Tiny
19STORMGSI90
  • MEMBER
Thank you very much I appreciate it.
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Sunday, September 18th, 2016 AT 8:14 PM
Tiny
AL514
  • EXPERT
NO BUS Light means no communication to PCM with one of several modules. What wire came unhooked off the battery? Was it the positive. This is a very difficult issue, with the research I have already done on it. And considering your ABS fuse keeps popping, I would say the problem may be in that circuit. Many people have run into this problem and it is usually not a PCM issue. First try unplugging the ABS module and see if your NO BUS light goes out. From what I have found, the way to diagnose this is to unplug modules until the NO BUS light goes out. But there are many. So lets start with your ABS fuse issue. If it keeps popping, there is a short to ground somewhere. Unplug both Positive and Negative off the battery first, then unplug ABS harness plug. Also check as many sensor connections as you can and make sure they are tight and making good contact. This NO BUS issue is a plague. It can be no communication between almost anything.
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Sunday, September 18th, 2016 AT 9:10 PM
Tiny
19STORMGSI90
  • MEMBER
Okay, do you have or know where I can Find a diagram of fuses and modules. Thank you very much.
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Sunday, September 18th, 2016 AT 9:14 PM
Tiny
AL514
  • EXPERT
I would start with the ABS module, if the fuse is blown just take it out and unplug the module, cycle the key off and on and see if the BUS light goes out. I would also try scanning the PCM for codes to see if anything is stored in the computer.
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Sunday, September 18th, 2016 AT 9:31 PM
Tiny
AL514
  • EXPERT
I have read it can also be in the instrument cluster itself, so start somewhere you have already found a problem (ie the ABS fuse). It can be so many different things, any number of sensors that have shorted out or something simple like a lose connection somewhere. But that fuse is not a good sign to start with.
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Sunday, September 18th, 2016 AT 9:35 PM
Tiny
CARADIODOC
  • EXPERT
I am here to save the day. Well, at least that is my fantasy.

The PCM is the Power Train Control Module. That's Chrysler's name for the Engine Computer. That does not have anything to do with the anti-lock brakes.

The data buss originates in the Body Computer and is the wires the dozens of computers talk back and forth to each other on. Be sure to check the fuses under the hood and inside the car. You will have to visually check the big ones under the hood, but for the smaller ones, there are two tiny holes on top, one for each test point. Use a test light to check for voltage on both test points for every fuse of that style. The ignition switch must be in the "run" position or the engine should be running. Some fuses will have 12 volts on both sides. Those are good. Some will have 0 volts on both sides. Those circuits are currently turned off and are not related to this problem. You're looking for any fuse that has 12 volts on one side and 0 volts on the other side. Those are blown.

There is a current surge that can cause nuisance fuses blowing when the battery is reconnected, and if the cable clamp was loose and arcing, it is even more likely multiple fuses would blow for no reason. A blown fuse is the cause of the "No Buss" message in the odometer display over ninety nine percent of the time. When it goes down, the computers cannot share information about operating conditions, sensor readings, and systems the driver has turned on. Also, it is the Body Computer that tells the other computers to wake up and do their thing, so with no data buss, none of the other computers will work. The fact the Engine Computer is letting the engine run suggests there is a back-up mode that allows limited functions so you are not sitting on the side of the road.

At this time I do not have a good answer, (or one that I can make up), for the anti-lock brake fuse problem. I have a trick for powering up a circuit for testing while preventing another fuse from blowing, but in this case there is just a computer and a hydraulic controller to look at. Simply unplugging them should stop the fuse from blowing, and plugging just one of them in will identify which one is causing the problem. Neither one has a history of shorting, but if I were to guess, I would suggest the computer. All computers have a diode in them between the 12 volt feed wires and the grounds. Diodes are one-way valves for electrical current flow. In one direction they act like a dead short, or piece of wire. They are installed in this application backward. That makes them become a dead short when the battery is connected backward. That short forces the fuse for that circuit to blow, thereby saving the rest of the circuitry. All you need to do is connect the battery correctly, replace the blown fuses, then look for other things that might have been damaged.

For the running problem, "it is not right" does not give us anything we can analyze. That is like telling your doctor over the phone that you are in pain. Unless you are specific with the symptoms and observations, he has no idea if you have a hang nail, a stomach ache, you cut your foot off with a chain saw, or your ex-girlfriend came back. The Engine Computer and Transmission Computer in particular go through a learning process as you drive to learn the characteristics of various sensors and the amount of mechanical wear inside the transmission. Some of that information is relearned within a few seconds. Some requires multiple drive cycles when a specific set of conditions are met. For example, when the battery was disconnected and reconnected, idle speed will usually be too low until the Engine Computer relearns "minimum throttle". Until then you might have trouble getting the engine started unless you hold the accelerator pedal down 1/4", you wont get the nice idle flare-up to 1500 rpm's at start-up, and it may stall at stop signs. The conditions needed to trigger that relearn are to drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals. That is the most complicated relearn requirement, but when people aren't aware of it, I have read where they have replaced all kinds of unneeded parts and the problem is still there.
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Monday, September 19th, 2016 AT 12:02 AM
Tiny
AL514
  • EXPERT
Agreed!
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Monday, September 19th, 2016 AT 3:17 AM
Tiny
19STORMGSI90
  • MEMBER
Thanks you guys so much for the help. Do you guys know where I can find a fuse diagram. I don't have one.
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Monday, September 19th, 2016 AT 1:40 PM
Tiny
KEN
  • ADMIN
Hey there,

I found these wiring diagrams for you.

Please let us know what you find so it will help others.

Best, Ken
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Saturday, September 24th, 2016 AT 4:18 PM

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