maxpower wrote:

> > Where the hell else is this bus going to ?!?!?!
> >
> > Does anyone know which pins on the 2 cluster connectors is
> > this bus?
> >
> > Is it 2 wires, or one?
>
> P1687 No communication with the MIC (mechanical instrument cluster)
> and as I stated in my first reply You need to verify if this is a
> total bus failure, or just simply a component issue.

For the brief time that the PCM was talking to the MIC, the 1687 code
was the only code coming through. Tells me that the PCM was talking
(has been talking) to everything else ok.

> For instance the gages can drop out if there is a bus failure,

I think it's more like they _will_ drop out if there is a bus
failure. All guage data seems to come from the PCM - no MIC guages
are wired directly to any sensors or transducers.

> if the cluster itself lost power or ground,

Of the 17 pins spread between the 2 dashboard MIC connectors, I've
metered 7 of them to ground. One comes from the battery directly
(it's always hot), and 2 others are hot when the ignition is turned
on. The MIC odo display comes on nice and strong, and so do the
indicator lights and the background illumination. So basically I
think the MIC is getting all the ground and power it needs.

> or if there is an internal cluster or pcm failure.

If the PCM's bus driver was faulty, then the "no buS" message on the
MIC should go away when I unplug the 3 connectors on the PCM - no?

When I unplug the MIC, the "CCD" message on the overhead display
should go away - no?

> If anyone of the modules, connecters, or ccd (bus) wires ...

From a physical point of view, is this bus a single common wire that
makes a simultaneous connection to all modules, or is it daisy-chained
into and out-of each module?

> The MIC (mechanical Instrument Cluster) is what creates
> the bus voltage.

???

If all the modules spew data onto the bus, then theoretically they all
"add voltage" to the bus. And - what's this about "bus voltage" ???
How can the state of bus functionality be measured by looking at the
voltage of the bus? If it's digital data, then I'd need a scope to
assess the health of the bus - not a volt meter - no?

> The ccd bus voltage should 2.5 volts, you can use a dvom and
> check this at the data link connecter.

Again, is the bus a single conductor (ie wire) using ground return -
or is it an isolated twisted-pair?

Is it wired as a common conductor between all modules, or does it go
into and out-of each module in daisy-chain manner?

> Ok do this, First check to see if you have 2.5volts at pin 3
> Vt/br wire of the data link connector and pin 11 wt/bk at
> the data link connector (The data link connector is the
> connector that the Scan tool connects to under the dash
> by your knee)

Ok, I'll check that - but here's what I don't get.

If this "CCD" bus is so great that Chrysler had to call it the
"Chrysler Collision detection bus", then what is that doing at the ODB
scan port (isin't the ODB port supposed to be manufacturer-independant
and use some other whacky and overly-complicated way to deliver data
to the outside world?)