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What does "no bus" mean?

87K views 40 replies 16 participants last post by  GILBERT BLOCK 
#1 ·
while driving my new to me 1999 5.2 Durango it just died. In the odometer it said "no bus" and the truck wont start...need some help please.
 
#5 ·
PCM is dead.

Either that or some of the wiring to it has come loose or corroded.
That would be my guess. In the world of computing a bus is something that allows data to be communicated between different pieces of hardware.


That said, it might me something completely off-the-wall because engineers love to screw with people. I recently stumbled upon the meaning of the infamous printer error "PC LOAD LETTER" and the meaning is ridiculous! "PC" stands for "paper cassette" instead of "personal computer" like every normal person would assume, and "LETTER" refers to 8.5"x11" letter-sized. What the hell is a paper cassette anyway? Has anyone in the real world ever referred to a paper tray as a paper cassette? Why didn't they make the error say "LOAD PAPER"!
 
#4 ·
Same thing happened to my Titan. A relay in the IPDM went bad, which controls the power to the computer - Truck died, but started up as if no issues. 10 minutes later, dead for good.

Cost me $181 for a new IPDM because apparently at the time you couldn't get JUST the relay - a year later Nissan released just the relay for $24.

Anywho.. the PCM should be an easy find/buy for $2-300?. Hell you may even get lucky and find one in a junk yard.
 
#7 ·
I had it towed to a shop today. They said the fault was in the CTM (centeral timing module) that is behind the glove box and the pcm by the passenger fender. Could it really be both sensors? It did start back up and drive this morning but died again a few miles later. I can get both the CTM and the PCM from eBay for about $300. The PCM is a reman unit programmed to my truck and the CTM is off another 99 Durango with my same options. I hate to spend that much money if you guys think it might be something simpler
 
#8 · (Edited)
It's highly unlikely, damn near impossible that BOTH are bad (the CTM and PCM are not sensors, they are computers). It sounds like they have no idea what's wrong if they are suggesting that both are bad. I'm surprised they didn't say the instrument panel was bad while they were at it. If anything it is just the PCM, but don't buy it just yet.

Did you try unplugging each of the sensors that I suggested one at a time? Start with the Crank sensor.
 
#9 ·
Here, I went and looked it up in my reference..

Vehicles:
1998 - 1999 Dodge Durango 3.9L
2000 - 2001 Dodge Durango 4.7L
1998 - 2000 Dodge Durango 5.2L
1998 - 2001 Dodge Durango 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.
 
#10 ·
I will try that tomorrow if they will let me (the car is at the shop). What they told me is the previous owner had beaten on the pcm. It does look like someone was hammering a screwdriver into it for some idiotic reason. Anyway they said the cracked casing on the pcm could have let water in and shorted the CTM. They said there diagnostic computer could only comunicate with the pcm when the CTM was diabled and they showed a programing fault in the ctm. Does that sound right?
 
#11 ·
Was the PCM beaten up before you brought it to them? Do any marks on it look fresh and shiny?

They are full of crap that water got into it and did anything, because the circuit board is 'potted' (once fully assembled it is dipped in a rubbery goop that locks water out and protects it from vibration).

"Programming faults" do not cause this problem or any interference with the PCM. Another lie. Get it back from them, don't pay them anything, and fix it yourself (even if it needs a new PCM its nothing you can't handle installing). They are either shady or clueless (or both).
 
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#13 ·
On 99's, no-bus is a common problem.(do a search). Yes the factory information says to check grounds but the common fix has been to get a new PCM
 
#14 ·
Yes it is a common problem, and I already explained the known issue that causes it. Why spend $300 on a new PCM when a $30 sensor could be to blame. Shotgun mechanics is a lousy (and expensive) way to do things. You don't just throw parts at it, you have to figure out what the problem is.
 
#15 ·
Not shotgunning. Out of the many post I've seen on this, I don't believ I have seen any that indicated other that other than PCM fixed it (including a coworker and the person I sold my original 99 PCM to)
 
#16 · (Edited)
Yeah you have, there are many. Including a couple you've posted in, insisting that it HAS to be the PCM, giving your list of reference links (and you are ASSUMING that your pcm fixed the person's problem because you claim you never heard anything back from them). And in one of those threads was a link to another thread, where I took the same position as you dismissing the fact that it could be a sensor issue, and I KNEW I was right an there was no way a bad sensor could knock out the PCM and it HAD to be a new PCM.. And know what? It was the CKP. Boy did I feel stupid. I (along with bogieboy) even made a public apology to l1tech (who we both thought was off his nut) over it. In fact, that very thread seems to have been bumped by a newb a couple days ago..

So once again, don't brush off testing the less obvious (and much less expensive) causes. What if he buys a new PCM and still has issues because the CKP is still shorting out?
 
#17 · (Edited)
If you are still reading this, I will let you know what I did. I searched high and low for someone to tell me what the solution is. All I found were horror stories about people spending all kinds of money on sensors and not getting the problem fixed. It is definitely heat related. I have a 99 Durango and the problem started when I hit 100K miles. I was usually able to restart the car within a couple of minutes. Then I had the Linclon Tunnel nightmare in Manhattan. I couldn't get out of Manhattan because I was afraid to go into the tunnel. All of this was happening in the summer of 2010. I went through the entire winter of 2010/2011 without the problem. As soon as the weather got warm in May, it happenned again. The problem is the PCM on the fender, passenger side. It pisses me off that Dodge can screw up a simple PCB. I design electronic equipment that goes on fighter jets. We sure as hell don't build crap like this. It gets hot under the hood, and either a component cannot take it or the PCB has developed an intermittent open. I changed the PCM and the problem hasn't reoccurred this summer. It is plug and play. I am told the dealers want like $600 for the replacement PCM and then they charge you more to program it. I got a PCM from Auto Computers for $225 dollars. They program it for you and all you have to give them is your VIN number and the miles on the odometer. The part number is P5640147AD. I am going to take the old one apart and see if I can find a problem. I will let everyone know if I find something.
 
#18 ·
I am waiting to get my pre programed PCM from a buisness on ebay. It was supposed to cost $230 but they had made a mistake on the buy it now price for $175 (that was supposed to be the opening bid price not the buy it now price. I got them to honor the price when I called in to give them all the info for programing. It should be here by Tuesday so I'll give you all an update at that point. As for the CTM, I bough a new one of those as well. Although it did allow the car to start, it did shut down about 30min later with no bus again. So the PCM must be the fix...Knock on wood!
 
#21 ·
I am waiting to get my pre programed PCM from a buisness on ebay. It was supposed to cost $230 but they had made a mistake on the buy it now price for $175 (that was supposed to be the opening bid price not the buy it now price. I got them to honor the price when I called in to give them all the info for programing. It should be here by Tuesday so I'll give you all an update at that point. As for the CTM, I bough a new one of those as well. Although it did allow the car to start, it did shut down about 30min later with no bus again. So the PCM must be the fix...Knock on wood!
Have you tried testing the sensors at all or are you just happy throwing away money that might not fix it like you did with the CTM?
 
#20 ·
VIN does not have to be programmed. I've now had four used PCMs in mine. All with the previous vehicles VIN. It has nothing to do with the secuity system which I also have.
 
#23 ·
Uhh no, it wouldn't have shown up on their scanner. That's the whole point of the TSB is that it shows no symptoms other than mimicking a dead PCM. They have to get out a friggin meter and test each sensor like the TSB says to. You're not under their control, you can have it towed back to your place for less than what you'll waste on parts that aren't the problem.

Like I said, you've already wasted money on a CTM after you were told it's not the problem. You really want to drop more on a PCM that's not the problem? And then still have to replace the bad sensor?
 
#24 ·
Just as a quick udate the new PCM did fix the problem. I've drove it for two days now without the dreaded "no bus". I do have a couple new symptoms now though. The Truck still stalls on occasion which it did before the computer problem. Usually when you first start it and shift into reverse. And after the new computer was installed now on occasion the (ABS) and brake lights come on but when checked the systems are working fine???
 
#26 ·
I have to say that this thread is very timely as I just picked up a 2000 Durango that has had an intermittent no start problem and now has a no bus and I still haven't seen it even try to start. But this is where it get interesting. I checked with the shop I got it from on what other work they may have done just to get an idea on any new parts, etc. They put a transmission in it shortly before this problem started. It wouldn't be the first time a wire got nicked or pinched while installing a transmission, intake manifold, etc. It's too dark now, but I know the first thing I'm checking tomorrow.

I will also concur with the guys telling you not to just throw money at the vehicle. We've all done it more than once, but we try not to.
 
#27 ·
Have 5v on the reference at the TPS, connected and disconnected. Didn't have a chance to check for anything else including a shorted bus. Maybe this afternoon.
 
#28 ·
Did you try resetting the PCM (pull the battery)?
 
#31 ·
I'm not sure what ground wire you fixed? What circuit is it part of? I changed out the PCM and I haven't had a problem since, as I knock my head against a wooden table. There is just no excuse that Dodge whould have for these kind of failures. It is such an easy electrical circuit, and the design of the board and the components should be good enough to handle the temperature and vibration environment they are subjected to. That's one reason I also drive a Maxima too. Five Dodges later and I don't feel fully satisfied. These cars are cheaper, but then you wind up with problems like this that can cost you a fortune to fix if you need someone else to do it for you.
 
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