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Durango "no bus" signal codes 720-721-999 #741640
07/06/10 11:29 AM
07/06/10 11:29 AM
Joined: Jun 2008
Posts: 1,506
Indiana
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GrnMagic77 Offline OP
Peter Parker
GrnMagic77  Offline OP
Peter Parker
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Joined: Jun 2008
Posts: 1,506
Indiana
More problems...99 Durango.
I've done a bit of online searching and it would seem this may be a common problem.Anyone else here had to deal with this on these era trucks?

Started off with fuel gauge not working..no big deal right? Next to die was the speedo and tach.It went from not wanting to start and having to fiddle with the key to now just not starting at all with a no bus signal on the odometer display.I have just replaced the crank sensor and disconnected battery overnight to hopefully reset error codes but nothing has changed.

Is an expensive PCM replacement the only thing that will work?

(Aside from what would be my first choice,getting rid of all the computer garbage on this truck...I know intakes and carbs are available,is it possible to 'de-computerize' a '99 5.2 magnum motor? I know it is a good engine but this computer nonsense is about to get the best of me and have the whole truck junkyard bound.)


1978 Round Up-1977 Warlock-1977 Powerwagon Adven.- 1976 Blue "Macho"-1974 Charger-1968 Fury III -1966 Newport *
Re: Durango "no bus" signal codes 720-721-999 [Re: GrnMagic77] #741641
07/06/10 12:32 PM
07/06/10 12:32 PM
Joined: Feb 2010
Posts: 1,377
Ohio
Todd Offline
pro stock
Todd  Offline
pro stock

Joined: Feb 2010
Posts: 1,377
Ohio
Get a service manual if you dont already have one and find all the modules on the bus. Then unplug one at a time until the bus becomes active. That should be the culprit. If that doesnt work,try the wiggle test. Ofcourse its alot easier if you have a DRBIII scan tool

Re: Durango no bus code 720-721-999 [Re: Todd] #741642
07/06/10 02:38 PM
07/06/10 02:38 PM
Joined: Jun 2008
Posts: 1,506
Indiana
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GrnMagic77 Offline OP
Peter Parker
GrnMagic77  Offline OP
Peter Parker
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Joined: Jun 2008
Posts: 1,506
Indiana
Thanks...I did go through unplugging the cam,crank and throttle position sensors one at a time with key on but it didn't really seem to make any difference.I have also unplugged each plug into the computer itself one at a time along with the engine wiring plug in the underhood fuse panel but the most I've accomplished is hear clicking.I still have the 'no bus' message,the engine will crank but fuel pump will not kick on and no fire to plugs.

Does anyone know if there is a reason why you cannot just disconnect the computer and take it into a dealership for testing?I have just called the nearest one to me which is about 27 miles away and would hate to deal with a huge towing expense if there is an easier way.

I guess it's not possible to make this engine run without a computer so next question...anybody know how to install an LA engine/727 trans into a Durango?


1978 Round Up-1977 Warlock-1977 Powerwagon Adven.- 1976 Blue "Macho"-1974 Charger-1968 Fury III -1966 Newport *
Re: Durango no bus code 720-721-999 [Re: GrnMagic77] #741643
07/06/10 02:58 PM
07/06/10 02:58 PM
Joined: Feb 2010
Posts: 1,377
Ohio
Todd Offline
pro stock
Todd  Offline
pro stock

Joined: Feb 2010
Posts: 1,377
Ohio
cam crank and tp sensors are not modules. Unplug the cluster, Trans computer, ect. one at a time...







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