Inquiring minds... I was just remembering the twisted pair wiring that we use in all kinds of electrical/electronic circuitry. Telephone cables, speaker wiring, doorbell wiring, are all twisted pair, and many more twists per inch (better noise rejection).
Makes me want to make a trip to Lowes just to look around!

 

You must be busy, haven't seen you around in a few days.
did your sensors come in?

 

I have been on a trip WITHOUT my van for the last 8-9 days. My Landcrusier does not carry nearly as much stuff as the van!

anyway yesterday I installed coolant and manifold temp sensors, along with new crank sensor, but got NO Bus right away and would not start. Tried several times with no success... temp was about 80 degress outside

This AM, it cooled off last night, and with air temp of 69, the van started right up...

SO... heat related problem for sure...

I wonder if both my old and rebuilt PCM suffers the same problem? As of now the rebuilt PCM is installed. As I look back on this... temps at or below 70 will allow the van to run, but after running awhile problem crops up... stall then eventually NO Bus no start. Temps above 75 or so will give me NoBus right away, so no start.

I was thinking yesterday that having a permanent condition of No Bus might allow me to troubleshoot this more easily... but now I am back to where I was before... intermittant...

This weekend is supposed to be hot and humid. If I get No Bus right away I am going to put one of the PCM's in the fridge and bring it out and try it cold to see if that has anything to do with it.

ANY new ideas out there that might be temp sensitive?

 

Good to see you back.
I'm stuck on the NOBUS. From what I have found, the Cluster is what provides the voltage and termination for the buss. Have you checked at the DLC for the bias voltage and termination resistance? There should be 2.49v on one wire and 2.51v on the other to signal ground. The Cluster provides the 5v reference. Measure the resistance between the wires. I think it should be 120 ohms with just the cluster connected, and half that with the PCM connected (it also has a 120 ohm termination).
http://mdhmotors.com/can-communicati...ork-protocols/

 

Friar,
glad for your assistance... but,

I have started and run the van without the cluster installed on more than one occasion... in my schematics the buss termination and the 5V supply for the sensors come from the PCM... I would include the schematic to prove this but I gave the FSM to a mechanic friend of mine to look over the other day to see if I was over looking anything... the more I get into this the more I think I have two bad PCMs, (as unlikely that I think that is) both exhibiting the same problem... that problem might be intermittent termination of the buss causing the NoBus condition, and also causing the stall/restart when running. I have believed there was one common cause of this irrespective of the two PCMs, but now I am not so sure. I am sure that it IS HEAT related now as on cool morning it will start, but not on hot days (NO Bus).

I have checked the DLC for 2.51-2.49 voltages numerous times... they are there until NoBus occurs... then disappear...

I have one PCM in the fridge, and when I get back out to work on this and get NoBus I am going to stick the other one in and see what happens... I tried freeze spray but the PCM is too large to cool effectively and freeze spray too expensive.

 

I was talking about the 5v reference for the BUSS only. Not the sensors, I know that's from the PCM. There should be a termination resistor in the cluster, as well as the PCM. Easy enough to verify, just disconnect and check between the 2 pins on each. If there's 120 ohms, it's a terminator. The documentation says it's ok to have 2 terminations.
Hmmm... Did you ever get any voltage at the DLC when the cluster was disconnected? Probably not. I have not found anything that says that anything but the cluster provides power for the BUSS. That is, I think, in the link I sent.

 

Friar...
thought I had eliminated the cluster as the source of the problem, however you have a point that I will investigate further...
thx

 

I can't stand the suspense, is it soup yet?

 

clean

 

Sorry, my first message was out of time and is just on top of this one.
Let see, I m following you guys for a little because I do have the same problem in my 2002 Dodge Ram Van 2.5 liters 318 engine, all are questions and no many answers, maybe one more in the conversation clear a little the concept.
Do we know how the communication is established between the PCM and the cluster? evidently have to be by cables. are these the #27 and #29 in connector C3 on the PCM.