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Discussion Starter #1
Hi, am new to this forum. 1st all I have to say this forum has helped me out many times on my 1999 and 1997 S10s. Reaching out because I’m stuck on this one..., my 1997 S10 speedometer is reading way fast. 2.2l automatic, ext cab. Has factory size tires on it and correct rear gear ratio (4.10). I’ve replaced the VSS, and have changed the cluster. Still getting the same result. At 70mph on my GPS, the speedometer on dash reading 100. Doesn’t matter what speed it reads fast. The slower your going it’s still fast but the faster you go, the farther it is off. I took it to a local performance shop where the guy with his laptop using HPtuner, couldn’t get it to change. He’s telling me from the VSS to the ECM is reading right, but from ECM to cluster he can’t change it. Need help on this please. Is there something else other than the ECM that could be causing this?
 

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Welcome.

Moved to Electrical/Lighting.
What year was the new cluster out of? Was it from a 2.2?
 

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If you have correct info in and garbage out doesn't sound like you have much choice. I don't understand why he couldn't change it with HPT, tho. That's one of the reasons a lot of guys buy HPT, so they can change tires and wheels. Unless he didn't have the license for your vin. You can read w/o paying, but it's $100 to write.
 

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Discussion Starter #6
He said he was able to increase the speed on the odometer, but it wouldn’t take the value to decrease it. So should I just purchase a pre programmed ECM for it?
 

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I was marketing a unit before they came out with HP tuners that will allow changing the pulse count + or - about 200%.
It modifies the signal either going into the PCM or out of it.
You read how far off it is and set the value with DIP switches.
The unit does require 12vdc to power it.
alot of guys like them because they can change to bigger tires and back to street ones and only flip a couple switches,no reprogramming.
This also works for rear gear changes. PM me if interested.
 

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I can change tire size with my Snap-On solus edge on my Jimmy (2000). Also changed it in my S10 (2002) When I was running non stock size tires. Was able to return to original size later. Not sure if you can do this on a 97.
Do you have a scan tool you can use to compare computer MPH to GPS?
 

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Discussion Starter #10
Still riddle me this...., stock tires, stock rear end, original transmission, changed VSS, and changed clusters...., what else other than ECM could effect speedometer?
 

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I just pulled out the 97 2.2 wiring diagram. From the VSS to The PCM - pin A ppl/wht goes to C1-63. Pin B lt/grn&blk goes to C2-52.
The PCM pin C2-15 green wire goes to instrument cluster pin #10.
THA-THA-THAT'S ALL, FOLKS !
No other wires going anywhere.

Is it possible in a past life with a different owner that the PCM was replaced with one from another 97 4cyl S10 that had it's program altered? Only a 97 would work correctly and only from a 2.2. Other years or engines wouldn't work in a 97 Tutu. But an automatic one could have been switched with a std shift one.
That would not explain being off 30%. 10% maybe.

Others on here have bought from these folks with good luck. You'll only need to do the security relearn after installing it. Takes 1/2 an hour of turning the key on and off. No trips to the dealer.
S10 S15 1997 97 Engine Computer ECM PCM 16228016 2.2L - Programmed to your VIN # | eBay

See post #2
 

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Discussion Starter #12
I was wondering if maybe the ECM might have been swapped out from another vehicle..., seems likely. Thanks for the info on the wires. I’ll look into eBay.
 

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I doubt it could have come from anything else since they are pretty much 97 only, 2.2 only PCM's.
96 and 98 won't work nor will one from a 4.3. Could have come from a 97 Cavalier they used the same part number. But that would only be off by 13% since they had a 3.58 final drive ratio. Still no where near your 30% error.
 

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Discussion Starter #14
I’m leaning more towards the ECM.., I did some more reading online about other issues that could be it. One that caught my attention was about hard shifting on the transmission. Before I took it and had that guy hook up HPtuner, I had a hard shift from 1st to second. Hard enough the SES light came on eventually. After he hooked it up, the hard shift went away and now is very smooth through every gear. Also noticed it doesn’t down shift as quite as hard. Other thing is the bad fuel mileage. Barely 15 MPG. I’ve looked at the eBay link you gave me..., thinking about getting a PCM from them.
 

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No, 97 has a VSS and wires. See post #11. First paragraph.
 

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Discussion Starter #17
So installed new PCM pre-programmed from eBay. Speedometer is closer (5mph off at slow speed), but gets to be 15 mph off at 65MPH down the road... am lost on where to go now. Any help would be greatly appreciated.
 

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Could the speedo itself be bad? Since the only 3 hard parts in the circuit are the VSS, the PCM, and the gauge, it's got to be one of them. 15 off at 65 is still nearly 25%.
The other alternative is the black box Dakota Digital sells that you put inline and is infinitely adjustable.
 

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Discussion Starter #19
I'll try a different speedometer, out of a 1997 just like mine. If that doesn't work, guess next option is the box..
 
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