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Discussion Starter #1 (Edited)
Vehicles:
1997 - 1999 Dodge Durango 3.9L
2000 - 2001 Dodge Durango 4.7L
1997 - 2000 Dodge Durango 5.2L
1997 - 2001 Dodge Durango 5.9L
1994 - 1999 Dodge Dakota 3.9L
2000 - 2001 Dodge Dakota 4.7L
1994 - 2000 Dodge Dakota 5.2L
1994 - 2001 Dodge Dakota 5.9L



Symptom: Engine will not start. Gauges are inoperative. nO buS message displayed on odometer.



System: Body/Chassis Electrical, Emissions/PCM/Fuel, Engine Electrical



Codes: N/A



Problem 1 of 6:
The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted Crankshaft Position (CKP) Sensor.

Test & Fix: If the 5v power supply circuit is shorted to ground, the CCD bus is unable to transmit messages and the Powertrain Control Module (PCM) appears to be "dead". The PCM is not damaged when the 5v power supply gets shorted to ground, but does need to be reset by turning the key off for 10 second after the short is removed. Using a DVOM or labscope, measure the voltage on the 5v reference wire at the Throttle Position Sensor (TPS) or Manifold Absolute Pressure (MAP) sensor. If 5v is not present, unplug the Crankshaft Position (CKP) Sensor. Turn the key off for 10 seconds. Turn the key on and measure the voltage on the 5v power supply circuit. If the voltage is now 5v, replace the CKP sensor.



Problem 2 of 6: The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted Camshaft Position (CMP) Sensor.

Test & Fix: If the 5v power supply circuit is shorted to ground, the CCD bus is unable to transmit messages and the Powertrain Control Module (PCM) appears to be "dead". The PCM is not damaged when the 5v power supply gets shorted to ground, but does need to be reset by turning the key off for 10 second after the short is removed. Using a DVOM or labscope, measure the voltage on the 5v reference wire at the Throttle Position Sensor (TPS) or Manifold Absolute Pressure (MAP) Sensor. If 5v is not present, unplug the Camshaft Position (CMP) Sensor. Turn the key off for 10 seconds. Turn the key on and measure the voltage on the 5v power supply circuit. If the voltage is now 5v, replace the CMP sensor.



Problem 3 of 6: The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted Manifold Absolute Pressure (MAP) Sensor.

Test & Fix: If the 5v power supply circuit is shorted to ground, the CCD bus is unable to transmit messages and the Powertrain Control Module (PCM) appears to be "dead". The PCM is not damaged when the 5v power supply gets shorted to ground, but does need to be reset by turning the key off for 10 second after the short is removed. Using a DVOM or labscope, measure the voltage on the 5v reference wire (5v power supply) at the Throttle Position Sensor (TPS) or Manifold Absolute Pressure (MAP) Sensor. If 5v is not present, unplug the MAP sensor. Turn the key off for 10 seconds. Turn the key on and measure the voltage on the 5v power supply circuit. If the voltage is now 5v, replace the MAP sensor.



Problem 4 of 6:
The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted Throttle Position Sensor (TPS).

Test & Fix: If the 5v power supply circuit is shorted to ground, the CCD bus is unable to transmit messages and the Powertrain Control Module (PCM) appears to be "dead". The PCM is not damaged when the 5v power supply gets shorted to ground, but does need to be reset by turning the key off for 10 second after the short is removed. Using a DVOM or labscope, measure the voltage on the 5v reference wire (5 volt power supply) at the Throttle Position Sensor (TPS) or Manifold Absolute Pressure (MAP) Sensor. If 5v is not present, unplug the TPS. Turn the key off for 10 seconds. Turn the key on and measure the voltage on the 5v power supply circuit. If the voltage is now 5v, replace the TPS.


Problem 5 of 6: The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted wire.

Test & Fix: If the 5v power supply circuit is shorted to ground, the CCD bus is unable to transmit messages and the Powertrain Control Module (PCM) appears to be "dead". The PCM is not damaged when the 5v power supply gets shorted to ground, but does need to be reset by turning the key off for 10 second after the short is removed. Using a DVOM or labscope, measure the voltage on the 5v reference wire at the throttle position sensor (TPS) or manifold absolute pressure (MAP) sensor. If 5v is not present, unplug all sensors that are connected to the 5v power supply and disconnect the PCM. Check if either 5v power supply circuit is shorted to ground using a DVOM. If the circuit is found to be shorted to ground, repair the wire and the cause of the short.



Problem 6 of 6:
The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted Governor Pressure Sensor.

Test & Fix: If the 5v power supply circuit is shorted to ground, the CCD bus is unable to transmit messages and the Powertrain Control Module (PCM) appears to be "dead". The PCM is not damaged when the 5v power supply gets shorted to ground, but does need to be reset by turning the key off for 10 second after the short is removed. Using a DVOM or labscope, measure the voltage on the 5v reference wire at the Throttle Position Sensor (TPS) or Manifold Absolute Pressure (MAP) Sensor. If 5v is not present, unplug the large round connector on the driver's side of the transmission. Turn the key off for 10 seconds. Turn the key on and measure the voltage on the 5v power supply circuit. If the voltage is now 5v, remove the transmission pan and check for shorted wiring inside the transmission. If the wiring is OK, replace the Governor Pressure Sensor.
 

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casias
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330 Posts
Another common issue with the "no bus" warning is a missing ground wire. Dakotas and Durangos have ground wires on two sides of the firewall, as well as the inside both front fenders. If any of these are removed in the process of removing other components, this error will occur.

Follow the harness in both directions from the ECU, and look for any wires that are not attached.
 

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Ive got this problem right now. My odometer says NO BUS and my durango will not start. Ive replaced the PCM so thats not my problem. Ive checked the sensors, all except the govenor sensor. Does anyone know where the connector for it is? Ive looked under my durango but i still cant find the connector. Is there a pic that shows exactly where its at and what it looks like?
 

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casias
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Ive got this problem right now. My odometer says NO BUS and my durango will not start. Ive replaced the PCM so thats not my problem. Ive checked the sensors, all except the govenor sensor. Does anyone know where the connector for it is? Ive looked under my durango but i still cant find the connector. Is there a pic that shows exactly where its at and what it looks like?
Here is a description of where it is located. http://answers.yahoo.com/question/index?qid=20100121132018AANEiB5.
 

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Thanks alot but i was wanting to get some knowledge on the actual connector that sits on top/outside of the tranny. I know it is a 8-way connector that routes up to the engine compartment but i dont where exactly it is,lol. Ive searched online and have seen that if i had a short in the tranny to disconnect the 8-way connector but i have no idea where its at :)
 

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Hello all,
For some reason this post caught my eye.

I am an industrial controls engineer and currently do a lot of sub contracting for the big three out here in the D.

I have just recently seen the NO BUS error in my brothers Dodge Neon, had the same issue. I actually swapped his ignition relay with his AC Clutch relay (same relay number) And confirmed his ignition relay was garbage..... Why it displayed this on his dash and that being the cause? Um.. Not sure how the engineer who designed the fault code for his vehicle setup the alarms (which are hard programmed ladder logix in your vehicles main control center, i guess the ECM / PCM / etc etc)

Typically though a NO BUS fault is a fault that is saying, hey! I do not have BUS POWER (as in there is no communication power) thus, NO BUS, or BUSS OFF type of faults will be displayed. Allen Bradley's PLC controll modual cards have a similar function... So if you are getting a no bus fault.. I would think you may need to sit down with a print and actually figure out if you have a FUSE, a RELAY, a WIRE, or MODUAL issue.

99 percent of the time if its a RUNNING and fully funct. system,
its likely a FUSE, RELAY, or MODUAL issue. If not, obvious thing is a GROUND or perhaps even any variety of WIRE thats being fed in that electrical system between ignitions point A all the way to the main MOD being point B.

Having designed a lot of fault code... its strange to think how engineers have done the SAME thing for vehicles... To be honest it makes my mind hurt because some of it was just poorly designed and is junk........

Hope my post was worth while to someone though!
 

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casias
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Unfortunately, as these vehicles age, more electrical issues are coming up with the primary one being the "no bus" error. But like you said, this error comes up with a variety of causes. The most common, that I have seen is the ground wire under the stock air cleaner, or the ground wire in the drivers side fenderwell is removed while working on something. But the ground wires under each side of the dash can also cause this fault.

Schematics can be found at

http://search.ebscohost.com/

log in as User ID: tech Password: tech
 

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would have been nice if they designed the fault code to actually tell you which system to isolate down that its detecting the issue from.. i've had it throw ignition faults in some occasions.. nice catch on the schematics, hope it can help someone in the future !
 

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Wow you people really sound like you know what you're talking about :) i havnt got my Durango to start ever since i got the NO BUS issue back in july of last year. Ive put SO MUCH money in my durango youd think it was brand new. Lol. When you said module when you were listing the possible causes off the NO BUS im having what are the modules? Im sure you see what ive already changed or checked but im not mechanically inclined so teach me what i need to know in order to get my durango back running
 

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Well, its no bus, so... somewhere in your ECM or PCM mods, could be anywhere in the main feed of that, but that's just my best based assumption. Check ground / 24VDC / 0VDC lines on the ECM and PCM, might need to dig out the pin-out and schematics on it, will make it easier.
Would be a place to start I suppose?
You may test it all out and it works just fine,
well,
isn't that a head ache ? :\

If that's the case,
and it all tests ok,
look in your entire ignition system wiring and verify your main ignition starting circuit is proper and good (ignition relays, solenoid's, grounds, battery connections, etc.)
 

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Ok. I removed the gps and solenoid from the tranny and also disconnected the middle connector on the pcm and the no bus goes away and my fuel gauge and battery gauge works but when i reconnect the middle connector the no bus comes right back. Is it because i dont have a gps or solenoid connected THAT ISNT BAD when i have the 2nd pcm connector connected? Or is it something else?
 

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Discussion Starter #15 (Edited)
The middle connector contains the +5v lead that is shared by all those sensors listed above. So the fact that it works until you plug the middle connector in indicates that the PCM is good but you do in fact have a short in that circuit somewhere... If you have checked/replaced ALL of those sensors, then you have a wiring harness that has chafed/melted somewhere and the wire is directly shorted to ground..

Just to rule out an oversight, do step 5 again.. Unplug ALL of the sensors (TPS/MAP/CKP/CMP/GPS) and then plug the middle connector back in and see if it still says nobus. If it does, you have a shorted wire. If it doesn't, plug the sensors back in one by one until it faults again.
 

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I know the 1st connector to the pcm has a 5volt supply but i think the 2nd connector has a secondary 5volt supply also. Do you have any suggestions on what wire in the 2nd connector could be the problem? I hear that the 2nd connector is a common problem when it comes to a no bus, no start issue.
 

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Discussion Starter #17 (Edited)
The +5v (18ga orange) in the middle connector is for the GPS.. However if you have the 8-pin connector unplugged from the trans, that can't possibly be it. I didn't realize they used a separate pin on the PCM for it (even though it is connected to the same +5v source as the one in C1), I thought they were all on the same pin..

C2 contains nothing else but the injector drivers (ground output - would throw a P020x if shorted), sender inputs (ground input, would simply peg that gauge/reading high if shorted), three transmission solenoid outputs (ground outputs, but they go through the main trans connector), one transmission relay output (ground output, would throw a P0702 if shorted), and the alternator field (ground output, alternator would be putting out over 19v if shorted). There are no other power wires or bus wires in that connector.

I betcha if you test the orange wire (pin31) with the transmission unplugged, you will find continuity to ground - indicating it is shorted..

 

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Um how do i check for continuity? Do i connect the dvom to the tranny fuse connections where the fuse would go or directly to the wire that supplies the 5v supply on the middle pcm connector? And would it be safe to say that the gps is what is shorted?
 

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TazRango, if I unplug the center connector on the PCM and the no bus does not go away, would you recommend replacing the PCM or is there something else you recommend to try?

The vehicle died, then started again, then died on the interstate. Spedometer went from driving speed to over 120 and danced around before it died. Now no gauges work, will not start, and no bus error is displayed.
 

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Discussion Starter #20
Um how do i check for continuity? Do i connect the dvom to the tranny fuse connections where the fuse would go or directly to the wire that supplies the 5v supply on the middle pcm connector? And would it be safe to say that the gps is what is shorted?
No, test for continuity/low resistance between pin 31 on the harness and the chassis. If there is continuity or any resistance lower than a megohm, then the wire is shorted to ground somewhere. I just re-read your posts - did you ever get the 8-way connector unplugged from the trans?

If you have the GPS out and/or the 8 way connector unplugged when doing these tests, then no it is not safe to say it's the GPS.. How can a part that's unplugged be causing a short??

TazRango, if I unplug the center connector on the PCM and the no bus does not go away, would you recommend replacing the PCM or is there something else you recommend to try?

The vehicle died, then started again, then died on the interstate. Spedometer went from driving speed to over 120 and danced around before it died. Now no gauges work, will not start, and no bus error is displayed.
No, because the +5v in C2 only feeds the GPS. The primary +5v wire that feeds the sensors is in C1. However you can't test by unplugging C1 because C1 also contains the battery and ground feeds for the PCM. Did you go through and unplug all the sensors listed and see if the nobus goes away? Then plug them back in one by one until it comes back?
 
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