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chris2323

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I have a 1997 K1500 pickup and both my rpm and mph gauges are not reading correctly. They are both reading higher than the actual rpm/mph, and seem to get farther off as rpm or speed increases. Has anyone had this issue? Any help or troubleshooting advice would be greatly appreciated.

Rpm is 500-1500rpm off and mph is 5-15mph off. I have verified this by using scan tools and/or a gps speedometer. Mph and rpm are correct in the scan, so im thinking the pcm is sending the correct signal to the instrument cluster. I have tried 3 different instrument clusters and they all are off by the same amount. Please help!
 

ralmo94

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I was about to say swap another cluster in until you said you tried 3. Lol.
Also data stream is what I would also recommend checking. Now that you have exhausted the reletivly easy possibilities, another thing I think I would try is swap the pcm with another for diagnosis if you have access to one. Beyond that only thing I can think of would be to inspect the wiring harness.

Sorry I can't be of more help
 

PlayingWithTBI

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RPM and MPH inputs are 2 different things. RPM comes off the coil while MPH comes off the VSS and DRAC/VSSB. Maybe check your grounds and connections 1st?
 

User_name

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If you have a v6 a v8 cluster won't work for the rpm, if you have a v8 a v6 cluster won't work for the tach. Just an fyi
 

DonYukon

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So ive never had both at the same time but I had a Bad VSS that caused the same issue as you describe with your MPH
 

slovcan

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On my '97 the tach is accurate, but the air core motor for the speedometer was causing it to read 15-20% high. I tried 3 replacement instrument panels before I got one that only reads 10% high. I discovered the tach air core motor has the same number as the speedometer one, BUT the plastic "locator" feet are oriented backwards. I trimmed them and it will fit, but at that stage I didn't want to take mine out of the truck again to try it. I kept it for when this one starts reading higher again.

Also, the pre-95 or 96 (not sure which - have a different sensor setup than the newer ones. VSS? Not sure...
 

sewlow

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I have a 1997 K1500 pickup and both my rpm and mph gauges are not reading correctly. They are both reading higher than the actual rpm/mph, and seem to get farther off as rpm or speed increases. Has anyone had this issue? Any help or troubleshooting advice would be greatly appreciated.

Rpm is 500-1500rpm off and mph is 5-15mph off. I have verified this by using scan tools and/or a gps speedometer. Mph and rpm are correct in the scan, so im thinking the pcm is sending the correct signal to the instrument cluster. I have tried 3 different instrument clusters and they all are off by the same amount. Please help!
Do you have shorter tires than the OEM size?
 

chris2323

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RPM and MPH inputs are 2 different things. RPM comes off the coil while MPH comes off the VSS and DRAC/VSSB. Maybe check your grounds and connections 1st?
I checked all my grounds and wiring with a multimeter/test light. Went through everything i could without pulling the enitre dash. Still haven’t found whats wrong. Maybe i got some bad instrument clusters? The 3 clusters ive tried all have over 200,000 miles
 
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