LazyLemming

Hi folks,
Starting today I've been having problem with my 96 Z28 auto. The speedometer is bouncing around quite a bit, if I'm doing 55 or so, the speedo wobbles between 35MPH and 45MPH.

While this is happening, the transmission shifts back and forth a lot.

Does that sound like maybe a speed sensor problem? My best guess is there's an issue with the speed sensor and it's causing the transmission to not know when to shift properly...

Injuneer

Since the shifting is affected as well as the speedo, it would appear the problem is an erratic signal into the PCM, not an erratic signal out of the PCM to the speedo, or a speedo problem. Check for damage to the yellow and purple wires that run from the VSS to the PCM. Check for a loose connector at the VSS. Check PCM for code P0502. But that code should turn on the SES light.

LazyLemming

Heh... my SES is permanently on.

Cool, thanks for the specific info, I'll check it out. Glad to know I was on the right track thinking it was between the VSS and the PCM.

Injuneer

Why not fix whatever is causing the SES light so it serves a useful purpose?