Non-electronic transmission VSS
The Fitech LS ECM needs a VSS signal to allow shifting of the electronic 4L60e and 4L80e transmissions. The VSS sensor is part of these transmissions.
The ECM also uses the VSS signal to adjust fuel and ignition trim related to cruising speed and during deceleration. These functions can still be taken advantage of if you’re using a manual transmission or a non-electronic automatic transmission with a speedo cable outlet such as a TH 350/400, 700R, etc.
As the Fitech ECM emulates a GM PCM, the transmission VSS signal is expected to be 128,000 pulses per mile (PPM). No doubt this can't be changed in the ECM.
Dakota Digital offers two solutions for this:
1: Using the Dakota Digital in-line signal generator, number SEN-01-1 and the SGI-5E Universal Speedometer Signal Interface, 128,000 PPM can be produced. The SEN-01-1 is a speedo cable pass-through adapter and allows the original speedometer cable to be used.
2: The SEN-01-128 connects directly to a cable speedo cable output of any older transmission and provides 128,000 PPM directly. An adapter plug may need to be made by the user. This speedo adapter is NOT a cable pass-through adapter and cable driven speedometers can't be used.
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I run a TH400, how critical is this to have with the ultimate LS series efi?
I already have Dakota digital gauges, and they provide the 16k sensor as part of their kit...looks like it's a simple matter of getting the 128k sensor and connecting the fitech VSS signal at the same input location on the Dakota box (no splice needed then). Unfortunatly it's 115$ for it (vs 37$ for the stock dakota 16k sensor), so I'm curious to know if it's more of a "nice to have" or if it's really going to make a difference in the tuning and such, inquiring mind wants to know! 🙂
yes I would also like to know this , as I am switching from my TKO 600 to a thm 350.
thanks, axld
I have a problem with poping after letting of the throttle, gonna fix it soon when the parts come in.
When I let off at moderate speed the ECM thinks im not moving so it tries to return to idle and drops my timing down to 15 causing it to miss. Ill update if having a VSS fixes it or not.