A way to diagnosis moonie gauges?

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VIKING_MECHANIC

GMT 400 obsessed Swede.
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Is there a way to diagnosis the actual motor for each gauge? I swapped out my cluster on my 89 K1500 with a donor from an 88 and it's the same story as my original cluster. Speedometer doesn't work(actually stuck at 35) and fuel gauge doesn't work either.

Tomorrow I'm going to drive it while watching live data and see if the ecm is seeing a signal from the vss to at least try and rule out the body wiring.
 

DerekTheGreat

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I'm sure there's a way to diagnose the motors, but I'm not smart enough to know how. You're on the right path. If there's an issue with the circuit, ie the speed signal not getting to the ECM, it'll set a code. This is what the problem was in my case, but the solution wasn't obvious. It turned out the "BRAKE/RABS" fuse socket in my truck was trashed- which I overlooked because when I tested the fuse with my voltmeter, I got the "Beeeeeeeep" indicating current could pass through it. However, the one socket was corroded such that current was not being supplied. Once I swapped in a new socket, I had a speedometer once again. I can't help you with the fuel gauge, never had to mess with one on a GMT400.
 
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