Thetal1

I've got a ls1 swap 95. The issue in having is my speed is about half of what I'm actually doing. I had the comp Mail order tuned and after having a second local tuner check out the tune the tires and gearing was wrong. On top of that they couldn't let him change it. So we put on a new operating system and tried again. This time we could change it but the reading from the obd2 port and speedo stayed about half. It's a 99 computer and the harnesses have been swapped also from ls fbodies. The gauge cluster im not sure the exact year but its 98+.
The weird thing I that the comp matches the speedo even after all the changes to tires and gears with hp tuners.
Please help.

Thetal1

Let's try again. What tells the comp what my vehicle speed it? Is it off of the rear wheels or tranny?

Emdmechanic

iTrader: (2)

What transmission? The vss should be on the transmission. Did you tap the vss signal from the transmission to get the gauge to work or did you use the vss output from the ecm? You need to know what the vss sensor output signal is and make sure the pcm is calibrated for it . The pcm vss output can be changed to match the gauge you use.

Thetal1

its a t56. i did not tap any wires. the signal is coming from the vss through the cpm. The cpm is a 99 the tranny I'm not sure the gauges I'm not sure either. The weird thing is that no matter what gear ratio the tuner plugged into the comp it didn't change.
side note
i had to get a few different gauges due to the lcd readout being messed up and needles stuck. what do i need to do to calibrate it?

Emdmechanic

iTrader: (2)

What are you using to tune it? The transmission vss output needs to match in the tune.
Is the pcm seeing the correct speed? If it is then you can change the pcm vss signal output to match the gauge in the tune.

Thetal1

the guy is using hptuner. the comp matches the gauge but it is not the actual speed.
are the vss different from year to year? if so would i just be able to buy a 99 vss then that would avoid the issues?

Emdmechanic

iTrader: (2)

I dont know if they change from year to year. sounds like the output is correct . Its the input that needs to be tweaked. There should be a table that changes the signal input variable . 1k,2k,4k, 8k,10k, etc. You might have a bad vss to begin with . Or the sensor could be too far from the reluctor. On second thought ... the vss sensor should just be a pickup. The reluctor is what would change i would think . . Im just trying to throw ya ideas as im no expert in tuning.

Emdmechanic

iTrader: (2)

Its the reluctor that is different. Change the vss input to 11ppr and see if it changes the speedo/ecm output. on the third gen board i found this topic . up to 93 the trans used a 11ppr vss signal . 94+ uses a 17ppr signal. And after more reading ... If it is a 93 transmission , It can have the 11 tooth reluctor and a different vss. If the reading is still incorrect go with the 99 vss .

Thetal1

i need somewhere to start I'm glad you gave me some info. ill research some more. From what i noticed the sensor is the same. ill call the tuner later and see.
Keep the info coming i need to fit this cuz the gauge reads about 1/3 the cars actual speed.

Thetal1

would you happen to have a part number?

oange ss

iTrader: (50)

did you verify the inputs to the VCM from the VSS ?

Thetal1

We didn't probe anything. All I can say 100% is that the sensor is plugged in and the ecu says the same as the gauge.

oange ss

iTrader: (50)

"comp" ?

Thetal1

I got ahold of the tuner he said we need to put the values in manually. I'm not sure what that means but we will see. If it doesn't work I'll be back here

Emdmechanic

iTrader: (2)

Did you get this resolved?

Thetal1

I've been outta town. I'm gonna mess with it this week. I'll post the results up