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Dreaded No Bus and everything that goes with it

Piston
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Piston

Piston

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Posted

Hi Folks. I am looking for some direction with my no bus issue. I did a cab swap on my 02 2500 4x4 24 valve automatic trans. I just bought the truck and did notice the fuel gauge was acting up before hand but didnt notice anything else but then again I bought it as a project and got right to work. After I got it back together, I would get a few gauges acting up and every 3rd or 4th keystart, I would get a no bus message. Here is what I have now pretty much with every keystart -  No Bus message, Alternator not charging, None of the gauges are working, Starts off in 2nd gear - Limp Mode?,  no communication with code readers, O/D off selector not working, dash warning lights on, codes 920, 921, 999 on the odometer. I checked the voltage on the #3 and #11 pins of the OBD connector and have 2.44 on pin 11 and 2.45 on pin 3. I understand this is a communication error between modules and could also be an issue with the cluster as well but would like to know where to go from here.

Any advice or direction would be greatly appreciated!

Thanks!

  • Staff
01_Cummins_4x4

01_Cummins_4x4

Posted
  • Staff
Posted

What year is the cab that you installed on your 02? 

 

Did you use your all the existing wiring in your cab that you took off, or did you use the donor cab wiring? 

 

Did you use the original PCM from your old cab, or use the donor cab PCM?

 

IIRC if your donor cab is 98.5 - 99, or a 2000 year, you will probably want to use your original wiring from the cab you took off. I think 01-02 are the same, but you will still want to use your original PCM because it is programmed to your VIN of our truck, and will have all the factory features enabled on it.

  • Owner
Mopar1973Man

Mopar1973Man

Posted
  • Owner
Posted

Ok a little education on CCD Network systems.

 

First off remember that the PCM is the primary computer, not the ECM. So now the PCM wakes up and calls out to all the modules. This being ECM, ABS, cluster, stock stereo, etc. If there is any voltage issues on the bus it will fail to communicate. The bias voltage should be 2.49 and 2.51 volts when all modules stop talking. Now the bias voltage is created by the cluster. This means you need a minimum of the PCM, ECM, and cluster to operate the network. If there is any P1694 or P1698 codes then there are communication issues with either the PCM or ECM. 

 

Another thing is all modules are VIN locked. So making sure to have the ECM and PCM with matching VIN numbers helps a bunch and reduces the issues possibly. 

 

Make sure you have good solid +12V power to all modules, and no cracked fuses or corroded connections. Ground wise don't go running around grinding paint off the metal and redoing grounds. TRUTH! VP44, ECM, and PCM are grounded to the passenger side battery, there are no body grounds for any main modules! Don't waste your time doing all the body ground most of that is grounds for the lighting. 

 

Bad modules like a fried overhead console can and will make the CCD bus fail. The best thing to do is remove all the option modules like stereo, overhead console, etc. Again you need just the cluster, ECM and PCM and this should be all you need for fire up and no issues. If still having issues I would contact @Auto Computer Specialist and chat with them about this and possibly have the ECM and PCM looked at and tested.

 

ccd.jpg

 

 

Piston

Piston

Posted
  • Author
Posted
1 hour ago, 01_Cummins_4x4 said:

What year is the cab that you installed on your 02? 

 

Did you use your all the existing wiring in your cab that you took off, or did you use the donor cab wiring? 

 

Did you use the original PCM from your old cab, or use the donor cab PCM?

 

IIRC if your donor cab is 98.5 - 99, or a 2000 year, you will probably want to use your original wiring from the cab you took off. I think 01-02 are the same, but you will still want to use your original PCM because it is programmed to your VIN of our truck, and will have all the factory features enabled on it.

Hi. Thanks for the reply, The dash and all wiring inside of the cab is from the donor cab and it is from a 1998 gas truck. I was wondering in the back of my head if I should pull the dash and change the harness over as I still have the original cab. The PCM is from the original truck. 

Question - I have a friend with some parts - can I borrow a PCM from him to plug in to see if it will do anything differently? I understand that they are flashed to the VIN but will it work at all? 

thanks again!

  • Owner
Mopar1973Man

Mopar1973Man

Posted
  • Owner
Posted
2 minutes ago, Piston said:

The dash and all wiring inside of the cab is from the donor cab and it is from a 1998 gas truck.

 

Nope that won't work. The cab should be swapped over to all diesel electrical and then the PCM should be from the diesel cab. Gas PCM runs way different software and electrical.

  • Staff
01_Cummins_4x4

01_Cummins_4x4

Posted
  • Staff
Posted

The gas truck wiring will be different than your diesel wiring harness. You really need to install your original complete harness and related electrical components from your original cab first, and use your original PCM.

 

 

 

 

 

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Piston

Piston

Posted
  • Author
Posted
8 minutes ago, Mopar1973Man said:

 

Nope that won't work. The cab should be swapped over to all diesel electrical and then the PCM should be from the diesel cab. Gas PCM runs way different software and electrical.

Thanks --- just to clarify the PCM is the original from the diesel cab. I think I will pull the dash this weekend and put the original harness in it and see what happens before going any further. 

Thanks!

  • Owner
Mopar1973Man

Mopar1973Man

Posted
  • Owner
Posted

Yeah even though the electrical wiring is from a gas engine so that will cause problems. There is actually two separate wiring maps for gas engines and diesel engines. This can be seen in the Dodge FSM books that are in the download area of the website. 

Piston

Piston

Posted
  • Author
Posted
6 minutes ago, Mopar1973Man said:

Yeah even though the electrical wiring is from a gas engine so that will cause problems. There is actually two separate wiring maps for gas engines and diesel engines. This can be seen in the Dodge FSM books that are in the download area of the website. 

Thanks! It does make sense. Looks like my Saturday is booked! I will let you know if it clears things up. 

Thanks again!

Piston

Piston

Posted
  • Author
Posted

Hi again, Just a quick observation....I havent changed the wiring harness from the original diesel cab yet but today I started the truck to move it and noticed that most of the gauges were working and I didnt have a no bus message. I moved it and the trans engaged in 1st gear as it should and the alternator was charging. I took the opportunity, as I know it would be short lived, and hoked up the code reader and it communicated. I had the following codes: PO253 Injection pump low, 1689 No communication between ecm and inj pump, 1688 Internal inj pump controller fail, 1698 no ccd. I tried to clear and see if any were hard faults but as soon as I shut it off and restarted, no bus was back and I had no communications. 

My plan of attack is again to change over the harness and if there is still an issue, unplug the other modules to see if any of them are pulling they system down but I wanted to share this info as well to see if anything jumps out at you folks. 

Thanks again for your help!

  • Owner
Mopar1973Man

Mopar1973Man

Posted
  • Owner
Posted
2 hours ago, Piston said:

I had the following codes: PO253 Injection pump low, 1689 No communication between ecm and inj pump, 1688 Internal inj pump controller fail, 1698 no ccd.

 

What worries me is the P0253, P1688 and P1689 which could be a bad VP44. Then the P1698 is the PCM not communicating...

  • 1 month later...
Piston

Piston

Posted
  • Author
Posted

Hi again folks, Its been a while but I was able to pull the dash and swap over the wiring harness. I did notice a difference in the two harnesses. I got it all back together and really had no change. I noticed that the alternator was now not charging. I have noticed that if I pulled the battery terminals and reattached them, I could fire up the truck and it would act fine. Shut it off and restart and bam, no gauges and no bus and no charging. Wait for 20 mins, re start and everything ok, drive it and the fuel gauge and battery gauge would drop out. At this point, I think the PCM has given up because now I have absolutely nothing - no gauges at all, no bus message, 0920 921 and 999 messages in the self check, no charging, no communication to the code reader. I installed a fuse in the blue wire to the pcm a while back like outlined as well.  I put in another PCM from a friends truck (I know they are vehicle specific but what the heck) and I have all gauges but still get a no bus message and the od off light stays on - I am thinking this is a programming issue being from another truck. 

Sorry for the length but I wanted to post as much info as possible. 

Any direction is greatly appreciated! 

Piston

Piston

Posted
  • Author
Posted

.....also, how crucial is the bias voltages? I have 2.46 on the purple and 2.40 on the white at the DLC. 

  • Owner
Mopar1973Man

Mopar1973Man

Posted
  • Owner
Posted
1 hour ago, Piston said:

.....also, how crucial is the bias voltages? I have 2.46 on the purple and 2.40 on the white at the DLC. 

First off turn on the ignition and wait several minutes for the modules to all stop talking. 

 

Next, you measure the voltage. It should be 2.49 and 2.51 volts.

 

If you measure the voltage during communication is not going to be accurate at all.

Piston

Piston

Posted
  • Author
Posted
1 hour ago, Mopar1973Man said:

First off turn on the ignition and wait several minutes for the modules to all stop talking. 

 

Next, you measure the voltage. It should be 2.49 and 2.51 volts.

 

If you measure the voltage during communication is not going to be accurate at all.

Hi and thanks, I did let it sit for a few minuted before but just did it again and let it sit with koeo for 15 mins and still had the same readings. 

Piston

Piston

Posted
  • Author
Posted

Do you think that this slight variation in voltage could cause the issues I listed? And also have you seen this before? 

Great work!

Great work!

Posted
Posted

The diesel PCM is not grounded by the mounting bolts. The ground goes thru the 3 connectors and splices into a larger wire that goes to the negative term of the passenger side battery. Check / clean all connections. I did a cab swap too and had to change every harness on the whole truck even above the headliner and the door harnesses too.

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