"MoPar Man" > wrote in message
...
> I want to unplug the TCM and the airbag module from the wiring/control
> bus. 2001 RAM, 2WD, short cab, 318 (5.2L) with upgraded interior.
>
> There is a small plastic cover on the tranny hump under the dashboard
> held with 2 screws. I take that off and there's a big connector right
> there attached to something. Is that the airbag controller? If so,
> then where's the tranny controller?
>
> The HVAC cluster also has about 2 or 3 connectors (which I unplugged).
>
> I unplugged 2 connectors on the brake unit (I take it this is the ABS
> controller).
>
> I unplugged the 3 cables going to the PCM.
>
> I unplugged the DRL module.
>
> I STILL GET NO BUS MESSAGE, and CCD message on the overhead console.
>
> 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?
>
> Does it go to the ODB connector?

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 instance the gages can drop out if
there is a bus failure, if the cluster itself lost power or ground, or if
there is an internal cluster or pcm failure. Also the gages can drop out if
the ccd bus is shorted.. All of the modules talk back and forth over the ccd
bus. If anyone of the modules, connecters, or ccd (bus) wires get shorted to
power, shorted to ground or shorted to each other, or internally (module),
then the whole bus communication system will stop. In turn all
modules/components that are dependant on receiving the necessary bus
messages will not operate. For instance the GAGES and OVERHEAD need the
information from the pcm. A loose ground for anyone of the module can also
cause a corruption in the CCD bus.
The MIC (mechanical Instrument Cluster) is what creates the bus voltage.
The ccd bus voltage should 2.5 volts, you can use a dvom and check this at
the data link connecter. If the MIC has failed there will be no bus
communication between the modules.
The ccd bus cannot cause a die-out condition. The "NO BUS" may appear in the
odometer, and the truck may stall if the PCM is lost (locked up)

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) if you don't have 2.5 volts on both wires then using
an ohm meter (Battery disconnected) remove the cluster and test for
continuity from pin#3 of the data link connector to pin number 10 of the
cluster connector VT/BR wire. Then check pin#11 of the data link connector
to pin 9 of the cluster WT/BK of the cluster for continuity. if both of
those wires are good and you still don't have 2.5 volts check for 12v at
pin#6 of cluster.