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Problems with instrument panel

I have a Chevy 2004 Tahoe and I am trouble with my instrument panel flucuating while I drive. I have had the battery and alternater checked and both are fine…The panels will show wrong RPMS and Speed what is the cause of this

According to the schematic I’m looking at, these gauges are driven by ‘class 2 data lines’ that seem to trace back to the car’s computer. With the right OBD2* reader, one should be able to determine whether the computer reads the right road and engine speed. If that is indeed correct, it could be that the data is getting garbled by the time it reaches the gauge. That could be due to a loose connection somewhere.
At the risk of getting too technical: When you transmit data over one wire to a bunch of devices, usually it requires some sort of termination at the very last device. Often it consists of a simple resistor. Since a car is hard wired, they very likely built that termination into the last device on the chain. That could be malfunctioning.

*Pepboys, Advance Auto Parts and Autozone can read your codes for free. Perhaps they can read your engine speed as well. Mine can. Theirs probably can as well.

EDIT: Jeepers! This thread is old!!! I didn’t notice the date until just now.
Who is gravedigging??? Oh, I see…
Please everyone flag mrwhizard as a spammer so he gets booted. We don’t need his kind around here…

I checked the Mr Whizard web site and it looks legit. They must have an employee who hatched this scheme to search for old posts and resurface them to drum up business. Perhaps Mr. Whizard should contact Car Talk and be a sponsor and get business and support car talk rather than scamming and spamming.

@UncleTurbo-- when I started looking at this board today, I was afraid it was “National Instrument Cluster Failure Week”. I’m glad to kow that this is a spam by Mr. Whizhard.