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Old 10-24-2011, 06:24 PM   #1 (permalink)
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no bus - electrical issue

Having some issues with my truck, it's a 2002 dodge dakota quad cab 2wd with the 4.7 V8 and auto transmission.

I'm getting the code "no bus" on the odometer, and the security light comes on. The fuel pump isn't kicking in and there is no spark. The fuel pump does work (jumped the relay and heard it kick in). All the wires under the hood have been chased and relays/fuses checked. I tried to hook up a computer/code reader but the truck wouldn't allow it to do anything. The crank sensor and cam sensor are both good.

I'm thinking computer but just wanted to check here for any other suggestions/idea's before I go and spend way too much money at the dealership or wreckers.
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Old 10-24-2011, 11:15 PM   #2 (permalink)
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Had that same issue on a dodge 1500 I worked on a couple months back. We finally chased it down to a broken ground wire at the front of the intake manifold on the drivers side. Double check every ground connection you can find would be my advise.
Unfortunately that's about all I know.
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Old 10-25-2011, 03:09 AM   #3 (permalink)
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Thanks, there were actually a couple broken grounds but I fixed them and the rest were double checked.
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Old 10-25-2011, 05:33 PM   #4 (permalink)
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So is it running fine now then?
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Old 10-25-2011, 07:01 PM   #5 (permalink)
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Unfortunately no, that was the first thing I checked (and fixed)
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Old 10-25-2011, 07:02 PM   #6 (permalink)
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The shop I work for had two 1500's in for the same thing recently. Both were ecu's.
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Old 10-25-2011, 07:51 PM   #7 (permalink)
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I talked to the shop foreman today for the dealership and he was extremely helpful and gave me a few idea's to try (iod fuse, and leave the key on for 1.5 hours to reset the security system) neither worked, and leaving the key on killed the battery. He said they have a computer at the shop that will bypass the security setting (which all aftermarket computers can't do). Scan is $90 so I'm going to give it a shot. A friend of mine who is a mechanic and myself have at minimum 12 hours into this so it's worth the $90 to me.

New computer is $700 though

Last edited by frumpy; 10-25-2011 at 07:52 PM.
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Old 10-25-2011, 08:47 PM   #8 (permalink)
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You seem to be on the right track. Checked grounds, are you sure you checked all main grounds not just the obvious ones?

You are already aware that the PCM could be bad. But you need to make sure that the PCM has power and grounds at PCM. You mentioned the IOD fuse, if its popped it will cause these issues. One thing to try is to have someone try to start it while you are pushing and pulling on the PCM connectors directly. Wiggling any main harnesses etc.

Having the dealer scan it should give you a heads up as to whats happening. If the PCM is bad though, hence the "No Bus" there will be no communication. And also I don't think the security has anything to do with this because of the "No Bus" message.

One thing to add, I have heard that a bad Crank/Cam/TPS sensor can halt the Bus communication and shut down the truck. Apparently this can only happen on the 4.7L. You say the Crank and Cam sensors are good, Are they brand new? How do you know they are good?

That's all I got for now, Good Luck.
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Old 10-26-2011, 11:57 AM   #9 (permalink)
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I was trying to rule out pcm as they are pricey. I checked pretty much everything you had listed. I just got a call from the shop though and they said it is the computer. The dealership computer wouldn't hook up either but they managed to do something to bypass the computer and got the truck started and working. Looks like I'm out almost $1200 ($730 for the computer, $320 for diagnostics, install, programming of computer, plus taxes)
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Old 10-27-2011, 11:18 AM   #10 (permalink)
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new computer in and good to go $1230 later
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