To the right of the steering column

 

photos of no bcm next

 

here are photos i just took of the post where the body control module is not. 1 pic is peeking in at capped connector on left side of post(closer side to steering column) . all this is factory, and van runs without bcm. unless it is somewhere else

so is it possible to disconnect every module and sensor to see if the buss comes back on? and is it safe, after batt- disconnect to empty cap in airbag module, to reconnect batt- with airbag module disconnected?

 

I do the modules one at a time and cycle the key to check if the NO BUS goes away. Crank and TPS are the most common sensors to short the BUS. I have to tell you to disconnect the battery before messing with the airbag module. I sometimes take risks, you should not.


Disconnecting the PCM will give you a NO BUS in the cluster on it's own, so the PCM is not checked this way. I usually have a known good PCM to check that from the start. It saves a lot of BUS circuit checkout time.

 

TNtech...

what can you tell us is the difference between '01 and '02 engine control? Does my '01 use the CCD bus to control the engine? I lose OBDII connections when my nobus occurs and I think I understand that is the CCD bus is what OBDII connection is reading... correct?

What about the '02? does that use SCI bus? And is the SCI bus ignored on the '01 engine?

thanks for your help...

 

SCI is the communication from the data link connector to the module with the termination resistor (dominant module). You can sort of call it a diagnostic BUS. If you don't have a generation vehicle with CTM (BCM), then the dominant should be the PCM. SCI comm is a transmit and receive (2 separate wires) in order to read data for the entire car.

No matter the terminology of the BUS, single wire BUS is single wire BUS and the diagnostics will be mostly the same.

We work on about 6 different BUS arrangements now. It's tough changing thought processes on every different car. The BUS systems since about 2005, as they phased it in later on other models, are all two wire BUS and they are getting faster and faster.

 

TNtech
I have posted this pic before from the '01 FSM... it tells me that my BCM is the controller (source voltage) for the CCD bus... right? This is why I am looking at sending out the BCM to be looked at. I have two PCM's one old, one rebuilt, both give me the same condition. I could have two BAD PCM's, but then I wasted $300 on a rebuilt one... so I am looking at some other cause for my nobus condition. I have an '01 B2500 on a 3500 chassis...
the second pic is the sticker on the replacement PCM showing the VIN and mileage along with the part number.

Any light you can shed on this is greatly appreciated...

 

a mechanic I talked to this afternoon, suggested that a high mileage 5.2l engine with a stretched timing chain could be giving goofy or false signals to the PCM causing the PCM to shut down intermittently...
anyone think this is plausible?

 

Nope, never heard of such a thing.

 

You can see by that pic, that the BCM is dominant with the resistor and you can also see that one without a BCM uses the PCM. The dominant one will be the source for the data stream or, where the SCI circuits go to. You really need the flow chart for no communication to go through.


No, but like I said before, a shorted sensor CAN do that. That incudes cam and crank sensors as well. That guy is a little confused on the theory, unless he thinks a shorted sensor is a "goofy signal"