Why does the LS ECU need a VSS signal if I keep my old mechanical-speedo transmission?
Here is what the documentation says. Each point links to its source; details depend on your exact computer, harness and transmission.
- The SGI-5E converts an 8,000 ppm signal to 4,000 or 2,000 ppm to run an OEM cruise control or fuel injection computer. (Dakota Digital)
- Gen III LS PCM; third-generation F-body: A third-generation F-body cruise control module requires a 2,000 pulse-per-mile VSS signal, which the secondary VSS output can supply. (LS Engine DIY)
Confirm against the instructions for your exact parts before wiring. More: Tach and speedometer signals in our tuning guide.
Confidence: medium — sources disagree or are limited; check the sources below.
Community discussion
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Sources
- Upgrading to Gen III LS-Series PCM: Signal Output Guide — LS Engine DIY
- SGI-5E Universal Speedometer Signal Interface Manual — Dakota Digital