I have tuned a 96 silverado with a 5.3 swap from a 02 truck. The tach is working but it is not close at all to reading correctly, it will work in the scanner but not to the dash. Is this something i can fix in the tune or will a pullup resistor need to be added to the tach?tune 3.hptlog 2.hpl
If the tach is working, but just incorrect, you can change the tach low and high resolution until it's correct. Now you're at 6 and 6. How much is the tach off? I typically start at 8 and 8. If that's not enough to make it accurate, you can tweak it until it is accurate.
This is a copy and paste from another site. I have used this method and it worked.
OK, so she's running however if you hooked up your stock Tach or your aftermarket Tach it most likely isn't reading right, what did you do wrong? Well, most likely nothing, you see the PCM by default is putting out a tach signal suited for a four banger and not a V8, so let's fix that. I am not going to go into the science of how this works (24 tooth reluctor wheel, blah blah blah) just use this cheat sheet:
for 4 cylinders set it to: 6
for 6 cylinders set it to: 4
for 8 cylinders set it to: 3
Assuming you completed Part I and disabled your VATS already:
1. This time we start in the comfort of your own home, fire up your laptop and launch the Editor. Open the file we saved in Step 3 of Part I. (Now this is your new base file, assuming that it all worked last time).
2. Make changes in the Editor, we will make one simple change, we need to change the Tach signal from the number 6 to the number 3 (notice I did not say cylinders) We do this in the Engine menu, General tab, Tach Output section. Change both "Resolution" values to:
Resolution - High 3
Resolution - Low 3
[pause for mini rant] this is what I was talking about in Part I, proper developers would mask this insanity with an option that says Number of Cylinder: (had they done it, this post would not exist, lol) [unpause]
3. save the changes you made to a new file and call it something like "02 - VATS Disabled V8 Tach Signal"
4. now get in your truck, hook up your HP Tuner to the OBDII port and then your USB cable to your laptop, turn the key to the ON position, launch the Editor program, this time however you DON'T have to read the information / configuration from the PCM into your laptop because it is already there, after all it came from the laptop where we made changes last time and that same data was written to the PCM, so now just write the new changes to the PCM.
Note: sometimes you have to write the entire tune file to the PCM, sometimes it is perfectly happy with only writing what's changed, more on this later.
h that's better, but why is the Tach Output set to 6, is it for a 6 cylinder, I thought the PCM put out a signal for a 4 cylinder.
It does put out a signal for a 4 cylinder, 24/4=6 and that's all I know, ha ha and 24/8=3 and that's what we need to change both of those numbers to is "3"
by the way 24 is the number of teeth on the reluctor wheel in our Gen III LSers
http://67-72chevytrucks.com/vboard/s...d.php?t=792225
I will try this. Thanks.
I am using 3 on my 5.3l swap with PSI harness and LS1 P01 ECU. Tried 6 like suggested and it was double the actual RPM. Autometer suggested using a resistor which didn't help, So I just changed the resolution until it worked.
What should i select for tach output-type?
Whichever one makes it work.Originally Posted by 04silverado6.0
I have a 1992 with a 5.3 with stock tach. I have tach output high 3 and low 3. Works perfect.
got an old '86 C10 with oem tach hope that work with change in pcm or resistor pull up
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