Dash gauge Problem with my 2004 Chevy Trailblazer.
ABS, seatbelt, battery, parking brake light. Installed aftermarket radio 4-5 months before problem.
Rebuilt instrument panel cluster.

All gauges in IPC are bottomed out except tach and speedo. ABS,seatbelt,battery,  and parking
brake lights constantly stay on.
Cruise control works, but indicator light saying I am in cruise doesn't appear.
Also, the gear indicator light telling me if I am in P,R,N,etc.. Doesn't highlight the gear I am in.

Had cluster rebuilt, problem still there.

1st question:
Could you possibly provide me with information that gives a pin out of my IPC harness and the  
voltages that should be there.

ECU location and the harness that goes to my IPC pin out with voltages.
I didn't make a donation because I wasn't sure if this information is available through this  sight,  
but I will gladly make one if it is.

After reading about the different problems with different seemingly unrelated indicators / gauges, i
looked through some schematics.
The thing that stands out is that then tach and speedo signal are given to the IPC from the PCM  
from their own, separate circuits. ALL the other indicators get their signal from the PCM, but on a  
different circuit. In other words, all indicators are feed from the PCM to the IPC on 1 wire, called  
the Class 2 serial data line. The speedo has its own wire, the tach has its own.

First be sure to check ALL fuses. Underhood fuse block, and block under the rear  seat.
If all ok, i would suspect either a PCM problem, or more likely a problem with the serial data wire  
between the PCM and the IPC.  
A continuity check of that circuit is probably your best / next check.

Question: My husband just acquired a 94 Chevy Silverado C/K 1500.  The instrument panel
doesn't work properly at all.  The odometer continues running when the truck is parked with engine
running and the speedometer shows 120 while we are sitting still in the driveway. He has so far:
Replaced the fuses in fuse box, tried a used replacement cluster and it did the same thing, and no
effect.  What could be causing this problem? Thank you for any help you can suggest :) Patricia.
You probably have a shorted out, or faulty vehicle speed sensor. If it's sending a reading to the
instrument cluster, even if the vehicle is not moving, the speedometer and odometer will keep
registering miles and mph.

You can try disconnecting the sensor, which is located at the rear of the transmission if it is a two
wheel drive truck or at the rear of the transfer case if it a four wheel drive truck. If you disconnect
it and the problem stops, you know the sensor is bad. If the problem keeps occurring, you have a
wiring problem somewhere along that harness that would need to be checked out.
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2004 Trailblazer Gauges Not Working