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Registered
2008 Saab 97x Aero
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906 Posts
Discussion Starter · #1 · (Edited)
Only had the saab two months or soo and just wondering why the speedo doesnt move when you nail it

Im just looking for the reason why dont need bitching or moaning cause im new and asked... Its not normal so I ask...

Doesnt bother me but it just doesnt make sense...
 

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Premium Member
TBSS 3SS
Joined
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1,991 Posts
Only had the saab two months or soo and just wondering why the speedo doesnt mov# when you name it

Im just looking for the reason why dont need bitching or moaning cause im new and asked... Its not normal so I ask...

Doesnt bother me but it just doesnt make sense...
Its because it doesn't like to be called names. ^69:biggrin2:
 

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Premium Member
2007 AWD - 3SS TBSS
Joined
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2,617 Posts
Has to do with the 3400 Stall speed Converter... Does it for everyone without a stock stall converter...
 

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Premium Member
'08 TrailblazerSS
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3,002 Posts
There is a way to fix it but it will require a second ecm.
 

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Premium Member
'08 TrailblazerSS
Joined
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3,002 Posts
Here is how the VSS works in a stock TBSS.

The raw AC voltage from the VSS goes to the tcm, the tcm compares that voltage with the iss signal, and then sends a buffered signal out to the ecm, which in turn generates a 4000 pulse per mile signal and sends that out to your IPC (speedo).


You need to get a spare ecm (E67 or E40, either one will work regardless of year)and flash it with a manual trans OS (if E67 use CTS-V OS, if E40 use SSR OS, I have both files and can email them upon request). Then you will need to copy your TBSS VSS settings into the spare ecm. You will also need to purchase connectors and pins for your spare ecm. Now you are going to connect power and ground to your spare ecm. Then you will tap both vss wires at the tcm and run them into your spare ecm (make sure you leave the VSS wires connected to the TCM). Then you will remove the Vehicle Speed Signal wire (the D-GN/WH wire that goes from the ecm to the IPC) from the TBSS ecm and connect it to your spare ecm. Now your speedo is being controlled by the spare ecm with a manual trans OS.
 

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Resident NIP
06 SS Trailblazer
Joined
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4,326 Posts
Here is how the VSS works in a stock TBSS.

The raw AC voltage from the VSS goes to the tcm, the tcm compares that voltage with the iss signal, and then sends a buffered signal out to the ecm, which in turn generates a 4000 pulse per mile signal and sends that out to your IPC (speedo).


You need to get a spare ecm (E67 or E40, either one will work regardless of year)and flash it with a manual trans OS (if E67 use CTS-V OS, if E40 use SSR OS, I have both files and can email them upon request). Then you will need to copy your TBSS VSS settings into the spare ecm. You will also need to purchase connectors and pins for your spare ecm. Now you are going to connect power and ground to your spare ecm. Then you will tap both vss wires at the tcm and run them into your spare ecm (make sure you leave the VSS wires connected to the TCM). Then you will remove the Vehicle Speed Signal wire (the D-GN/WH wire that goes from the ecm to the IPC) from the TBSS ecm and connect it to your spare ecm. Now your speedo is being controlled by the spare ecm with a manual trans OS.
What do you do for a living man? You've always been able to answer my wiring diagram questions...
 

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Premium Member
2006 TBSS 3SS
Joined
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17,602 Posts
I think the cause has something to do with the input vs output speed is outside a range originally designed into the OS by GM. As designed it probably should never see such a wide range.

So when its outside these parameters it doesnt know what to do.

Betting if the programmers at GM would go back and extend the tables (range) it would probably be fine.

Brandon, you are amazing. Always thinking outside the box :)
 

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Premium Member
2006 Red Jewel AWD
Joined
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11,641 Posts
There is nothing a tuner can do to fix it and having a 2nd computer on hand is a big waste of time. I have a schematic here somewhere that shows a way you can simply run a diode isolated jumper wire from one wire to the ISS sensor wire and it fixes the problem.

Let me do some searching!
 
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