Hey everyone. I was playing around with Tunercats with a 1992 SD chip. I noticed under the Flags that there was a flag called Vehicle speed diagnostics(error 24). I initially thought that this was to turn off or on the electronic vehicle speed sensor. Then I checked out the .bin from my 1986 hypertech chip and it had the same box and was checked, but 1986 had mechanical speed sensor. So, I have two questions

1) How do I turn of the VSS for my 1986 Iroc with SD 730 ecm

2)What is the purpose of the Vehicle Speed Diagnostics(error 24) box? What does it do?


Thanks

Chris

 

You can't turn it "off". It's a vital part of the computers sensors. It controls things like highway mode EGR (I think), and the most important one I've found out the hard way. TCC lockup. Since my VSS wasn't the correct type for the 730 it was not locking up my converter creating alot of heat in the tranny. I was able to cook my transmission fluid in less then six months. You really need to pick up a 4000 pulse per mile AC unit with a speedo cable adapter from stealth tech. or turbo city.

www.turbocity.com

As far as the diagnostic, the box is there so if you don't have the VSS, it won't set a trouble code every time the car is started. That way you aren't running with the SES light on all the time.

 

I was looking at the '730 asm code and it shows that you can use an optical VSS (2000 ppm) and hook the brown output wire to pin C6 on the ECM. Then set the flag in the code indicating optical VSS. That's what I am going to do with my set-up.

J

 

What is a mechanical speed sensor? Are you referring to optical or magnetic?

J

 

I was unaware that there was a provision in the code for an optical sensor, I don't know where you got mechanical I was talking about a magnetic sensor that attaches to the tranny where the speedo gears are. I'm really not ready to jump into the asm. language so I'm just going to buy the new sensor.

 

The thread started with this comment in it from the Nuff guy....

Then I checked out the .bin from my 1986 hypertech chip and it had the same box and was checked, but 1986 had mechanical speed sensor. So, I have two questions

Anyway, you don't need to get into the asm. Run the Vss wire to C6 and set the bit in TC or Winbin.

J

 

If your using mask 8D, then change location 0018 from D8 to 98. Then feed the optical sensor to C-6.

 

Sorry. I meant that I have a mechanical speedometer with the speedo cable. I have a SD 730 computer, so will I have to change anything to read the correct speed in the computer? Break it down for me.

Thanks

Chris(got a lot to learn)

 

How do you set the bit in TC? there is only the diag. switch. I don't see any bit for 2000 v. 4000 ppm VSS, or are you talking about the diag bit? Thanks

Jim