10,000th "no bus" thread

[DownByTheRiver]

2001 3500, manual

 

A few months ago, 'no bus' showed up on my gauge cluster, and the gauges died.  Truck started and ran fine, but no gauges after a few seconds past startup.  Was driving it on short trips until it started stumbled and started getting loud fuel knock going down the road at 45.  Brought it home, let it sit for a week.  Next time I fired it up, it was smoking really good at idle, and cleared up when it was warm, but it's down on power pretty good once warm.  Codes pulled at this point are:

 

P0237, P0234, P1698, P0216

 

I reset the codes and only P0216 and P1698 came back.  

 

Gauge codes are 920, 921, 940 ,950, 999

 

I'm going to do the W/T ground mod and check my other grounds, because I'm wondering how the PCM and VP44 both miraculously crapped out at the same time.  Alternator to battery shows ~50mv of ac.  Ground test from pass fender ground to 31 of PCM C1 connector shows 0.1 ohms.  Have 12v B+ and IGN+ on pcm connector.  0.1 ohms at pin 31 of PCM is bad PCM according to FSM, so I shipped it off to a place last week and they said it was good, but I'm finding that hard to believe given what I've seen. 

 

Here's what they said:

Quote

 

We've finished with you're computer, Everything is responding properly.

 

We have alt charge, the data buss and all circuits are within specifications.

 

We do have scan tool communication, your VIN number was also extracted to confirm communication, 1B7MF33611J194471.

 

You might have a power distribution issue not sending power to the PCM or OBD2 port.

 

 

 

I guess I'm going to dig into CCD stuff next.  Any other ideas?

 

When I first got the truck a few years ago, the gauges weren't working, but I replaced the cluster and didn't have any problems until no bus.

 

I also re-did my dash two years ago and changed the CTM to the high line truck that I got the interior from.  My truck is a base model, but had to make the harness match. 

 

I figured this was all pertinent information, but I drove for a while before any issues of no bus came up.

Edited March 3 by DownByTheRiver

[Mopar1973Man]

Check the CCD Bus article 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/electrical/ccd-chrysler-collision-detection-data-bus-r329/

[DownByTheRiver]

On 3/3/2025 at 8:19 PM, Mopar1973Man said:

Check the CCD Bus article 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/electrical/ccd-chrysler-collision-detection-data-bus-r329/

 

Just read it, and thanks for the diagram. So what's the best way to test this, just start unplugging these connectors, or use a scope?

 

One more thing: I've had the ABS light on for a while, and one time I went to the dealer (to check the ABS code, and the tech said their DRB3 tool couldn't communicate with the module.   Unplugging the ABS connector doesn't make the gauges come back or no bus go away though.

 

I lose some gauges right away, but the others are delayed by about 5 seconds.  That, to me seems like component failure in the PCM.  The manual does say if the resistance of the PCM ground is less than 10 ohms, replace the PCM.  Mine tested at 0.1 ohms.    I'm doing the W/T ground mod anyway, but it seems like it may be too late.  Maybe alternator noise killed the VP44 and the PCM?  It was 50 mV when I checked.

[Mopar1973Man]

You could look towards @Auto Computer Specialist which is listed in our vendor listing... They can do PCM and ECM repairs. If the cluster is damaged then that can be handled by Module Masters in Moscow Idaho.

 

https://mopar1973man.com/vendor.htm/vendor/auto-computer-specialist-r5/?do=getNewComment&d=7&id=5