no bus - electrical issue - Pirate4x4.Com : 4x4 and Off-Road Forum

frumpy · 10-24-2011, 05:24 PM

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.

TheMissingLink · 10-24-2011, 10:15 PM

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.

frumpy · 10-25-2011, 02:09 AM

Thanks, there were actually a couple broken grounds but I fixed them and the rest were double checked.

grasshopper77 · 10-25-2011, 04:33 PM

So is it running fine now then?

frumpy · 10-25-2011, 06:01 PM

Unfortunately no, that was the first thing I checked (and fixed)

tom wade · 10-25-2011, 06:02 PM

The shop I work for had two 1500's in for the same thing recently. Both were ecu's.

frumpy · 10-25-2011, 06:51 PM

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

grasshopper77 · 10-25-2011, 07:47 PM

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.

frumpy · 10-26-2011, 10:57 AM

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)

frumpy · 10-27-2011, 10:18 AM

new computer in and good to go $1230 later

10-24-2011, 05:24 PM	#1 (permalink)
frumpy Registered User Join Date: Nov 2006 Member # 82262 Location: Chalk River, ON Posts: 950	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.

10-25-2011, 04:33 PM	#4 (permalink)
grasshopper77 Registered User Join Date: Sep 2005 Member # 52872 Location: Where it's too damn cold. Posts: 310	So is it running fine now then? __________________ [COLOR="gray"]Horsepower is like a Condom.....I would rather have it and not need it than to need it and not have it [/COLOR]

10-25-2011, 06:51 PM	#7 (permalink)
frumpy Registered User Join Date: Nov 2006 Member # 82262 Location: Chalk River, ON Posts: 950	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 06:52 PM.

10-25-2011, 07:47 PM	#8 (permalink)
grasshopper77 Registered User Join Date: Sep 2005 Member # 52872 Location: Where it's too damn cold. Posts: 310	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. __________________ [COLOR="gray"]Horsepower is like a Condom.....I would rather have it and not need it than to need it and not have it [/COLOR]

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10-24-2011, 10:15 PM	#2 (permalink)
TheMissingLink Registered User Join Date: Sep 2011 Member # 199954 Location: Southern Utah Posts: 0	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.

10-25-2011, 02:09 AM	#3 (permalink)
frumpy Registered User Join Date: Nov 2006 Member # 82262 Location: Chalk River, ON Posts: 950	Thanks, there were actually a couple broken grounds but I fixed them and the rest were double checked.

10-25-2011, 06:01 PM	#5 (permalink)
frumpy Registered User Join Date: Nov 2006 Member # 82262 Location: Chalk River, ON Posts: 950	Unfortunately no, that was the first thing I checked (and fixed)

10-25-2011, 06:02 PM	#6 (permalink)
tom wade Newbie Join Date: Jan 2006 Member # 65721 Location: Moapa, NV. Posts: 34	The shop I work for had two 1500's in for the same thing recently. Both were ecu's.

10-26-2011, 10:57 AM	#9 (permalink)
frumpy Registered User Join Date: Nov 2006 Member # 82262 Location: Chalk River, ON Posts: 950	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)

10-27-2011, 10:18 AM	#10 (permalink)
frumpy Registered User Join Date: Nov 2006 Member # 82262 Location: Chalk River, ON Posts: 950	new computer in and good to go $1230 later