Stepper motor replaced, Speedo still not working

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kly5953

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I recently got a set of new bulbs and stepper motors to replace on my gauges. After swapping out the tach, it now works, and I swapped 2 different ones into the speedo, but the speedo is still acting weird. The first one jumped 10mph everytime I started the tahoe, and the second one never moved, then when I turned the vehicle off, after driving, it jumped to 10mph as well. It still isn't moving now that it jumped up to 10.
I'm wondering if it's the speed sensor. Does anybody have recommendations on what to look for now?
 
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kly5953

kly5953

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Is there anybody that has any input on this? Not having a speedometer is getting old. The speedo is now randomly reading over 120mph, then will just drop all the way to 0mph
 

Fless

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Put a scanner on it and see what the speed sensors are doing in live data. I'm not sure which one would drive the speedo but if you watch the sensor values while someone else drives, it might be obvious.

Have you tried another cluster in it?

If the truck has other issues that haven't been listed, a thorough examination and cleaning of the battery cables, body and engine grounds would be in order.
 
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kly5953

kly5953

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Every other issue has been fixed
water pump, MAF, Alt, serpentine belt, AC belt, washer reservoir, washer motor.
I am somewhat new to trouble shooting vehicles, and hoping that I can find the issue. I will say: I need a new oil pan gasket, as this one is obviously bad. Not sure if that can cause any issues.
 

khtahoe

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Pull the cluster and break it down so you can look at the circuit board. Look for heat discoloration around any of the surface mount resistors/diodes. If you find any, reflow the solder on them. My tachometer was acting flaky and it was a surface mount resistor bad solder joint. You see plenty of info on reflowing the ones for the PRNDL not lighting or dim, it can be the same thing on the guages as I found out. It doesn't take long to check and is an easy fix if that is the problem. My thread on the Tach: https://www.tahoeyukonforum.com/threads/tachometer-randomly-not-working-flaky-ok-sometimes.132885/
 

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Put a scanner on it to read live data, take it for a short drive, and look at what every speed sensor is reporting.
 
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kly5953

kly5953

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Put a scanner on it to read live data, take it for a short drive, and look at what every speed sensor is reporting.
what is the name of the sensor that I'm looking for? The handheld I have has weird names for everything and I don't see a straight "speedometer sensor" label anywhere.
 
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kly5953

kly5953

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Ok, I went ahead and replaced the speed sensor, as it's hard not to justify the 3 min of work and $11 part, but it's still not working. Reminder: everything else on the dash is good.
Does anybody know exactly what all I need to look at when I pull the board out of the dash?
It seems as if some of the soldering is damaged somewhere so I'll look for it but any direction on an exact location would be great.
 

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get a cheapy bluetooth obd adapter and download torque or torque pro (it's cheap) with that you can confirm speedometer info is being fed to the cluster. or to the bcm anyway.
I would start there.
or buy a tech2 clone they run about $300 but will allow you to diagnose pretty much anything on the vehicle
it wont point you to a specific point on the cluster board that could be bad but it's a necessary tool (same tool the dealer uses)
 

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