Replaced the oil pan on a 2002 Dodge Ram 3500 extended i[Van. I removed the Transmission and lifted engine 4 inches or so to replace the Pan. I was carefull to try and not damage any wires doing so. Once I put everything back together I'm receiving a "no bus" code on the dash. Below are the symptoms.


- None of the Gadges on the dash respond. No fuel, no amps, no water temp, no Speedo, no oil pressure, no digital gear selector box around the drive letters or numbers. (except when the key is in the aux position, then the digital selector box displays and moves accordingly when shifting)


- The Engine starts and runs fine.

- The Van drives but it feels like the trany isn't communicating properly.

- Electrical Grounds seem good everywhere. Some slight resistance in some areas but I don't think it's of any concern.

- All connectors seem to be ok.

- All Realys seem to function correctly

- Wires so far look good. I have pulled off 20% of the wrap on the wirering harness to look in the most problematic areas due to trany removal and engin lift.

- I have tried a different PCM and I get the exsact same responce again.

- All.other dashboard items work, Head light switch, horn, key, blower motor, Brake lights, signal lights etc...


I have spent 2 days trying to diagnose this issue with only a volt meter and visual inspections. I'm at my wits end. Any help to fix this "No bus" Code issue and get all my gaudges back up and running?


Thanks


Lee

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Check the harnesses on top of the trans. They are sometimes victims of trans swaps...... Since everything works, except the cluster...... it is going to be a wiring problem. ALL of the gauges get their cue of what to display from the PCM, even the friggin gas gauge.... So, for whatever reason, the cluster seems to be unable to communicate with the PCM. Do you have a factory service manual for your van? If you don't, you are going to want to get one.....

 

Ok. I'll get a service manual. in the mean time when you say the harness above the trans can be an issue on a trans swap,. Are you insinuating that a wire could have broke on one of the 3 connectors or a wire inside the harness could have been damaged? I image that the shift indicator wires are ok because the shift light in the dash responds correctly.

As for the shift solenoid hook up and the speed sensor I would hope plugging a Diagnostics computer into the system will let me know if it can't or can see those units... the only other 2 connections that lead down to the trans is the 2 O2 sensors on the egsaust. Cab see that seeing a "no bus" issue.

I also have another spare van the same year that has no issues with the computer system. I disconnected the shift solenoid cable from the transmission and it did not result in a "no bus" code. So in theory that would tell me that connector wire it's not an issue on the broken down van.

 

A bad/failing rear O2 sensor can cause a No Bus issue. That system is REALLY wonky..... It would be interesting to see if you can actually communicate with the PCM via the OBDII connector...... I would expect probably not.

 

That's interesting you say a faulty O2 sensor could cause a "no bus" code. Before the van was taken apart I did have a faulty O2 sensor code. I didn't replace it. if the sensor is bad could I not just unplug it for testing periods. wouldn't that help the issue? of course unless the wiring to the plug is the issue
.

 

It's most certainly worth a shot.

When chasing the No Bus problem, unplugging the sensors on the 5 volt bus (of which, the O2s are right up there on the list), and seeing which one you unplug that makes the problem go away, is one of the methods. Give it a shot. See what happens.

 

I was low on transmission fluid and once I topped it up the transmission operates and works perfectly. Whoops my bad! Therefore I have good communication between my PCM TCM and everything else in the van. Except, I still have no response on my instrument cluster and now have an ABS light on. Any recommendations on what I should look at next. Taking about swapping out my gauge cluster with the one that's in my parts van

 

If you have a spare cluster, most certainly give that a shot. Might try just reseating the cluster connectors, and see if it isn't just a bad connection.

 

Problem has been solved!

The PCM far left connector wires look like they had some crappy work don't to then on the past. wires had been cut and joined back together with butt connectors. wire had corroded inside the butt connector and lost its connection. The wire that lost its connection was one of the 2.5 volt data bus lines the white and black striped one to be precise coming off of pin 28. The second I got that connection fixed everything came back to life. Boy am I finally glad that's over. What a hassle but no more leaky oil pan and now the trucks ready for another 350,000 km.

 

Congrats!!!