[Gmecm] Class2 DIY tools?

[Phillip Kuhn]

Ok, I have reviewed the GM wiring schematics for this
vehicle and this is what I can tell you. The BCM is
NOT in control over the info coming into the cluster.
The cluster recieves it's data via the class 2 data
bus from the VCM (aka PCM) on this vehicle. Also, the
passkey system in this truck does NOT go through the
cluster, rather it is wired directly to the bcm which
sends data to the VCM. More than likely from what I
see in service information and from what you say the 2
problems that you are having are completely separate
and not related in any way, at least not by something
such as the BCM. I can send you some "real" wiring
schematics tomorrow of the cluster and passkey system.
In the meanwhile my suggestions would be to first
check ALL of the fuses as there are many that could
affect the operation of the vehicle. Second attempt to
perform a passkey relearn. And third, double check all
of your connectors to make sure all of them are
completely seated.I can assure you of this, when it
comes to passkey in particular, there is NOT any way
possible to perform certain functions without a tech 2
and any other scan tool is not capable of performing
those functions from what I have been told. Below is a
key learn procedure borrowed from service information.


1. Ensure that the battery is fully charged. 
2. Use a scan tool in order to clear the Passlock?
DTCs
3. Turn the ignition switch from the OFF position to
the CRANK position, and then to the RUN position. The
vehicle will start and then stall. 
4. Leave the ignition ON until the security telltale
turns OFF in 10 minutes. 
5. Repeat Steps 3-5 for 2 more times (3 times total) 
6. The Passlock? controller will learn the new data on
the next start 
7. Use a scan tool in order to clear all DTCs. 

I would at least attempt to do the key learn without
clearing the codes as I have never had to clear them
before programming a key. Be sure though, if you do
attempt a key relearn that your battery is charged
because if it dies in the middle of a learn it is
possible to ruin the passkey module.As far as possible
"common" causes of your original symptoms they would
be : loss of vcm to cluster communications, blown
guages fuse, bad vcm, or bad cluster. Those are about
the only things that would cause the original
symptoms. As far as the new problem you induced it
could be a number of problems relating to the passkey
module, bcm, vcm , wiring, fuses, or just simply a
lost password. I hope this sheds a little more light
on the situation,
Phil



		
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