I’ve got a 1997 Boxster and the tach (rpm meter) has started flickering/jumping, then dropping to zero under acceleration. At lighter throttle or lower RPM it’ll sometimes come back. Other gauges are fine, car drives normally, no CEL…

This started around the same time I installed an aftermarket single-DIN CarPlay head unit. I chased some RPM-related audio noise during the install and improving the grounds helped the noise.

Because it’s load-dependent and flickers before dropping, I’m thinking ground/reference issue, not a sensor?

Planning to replace the engine/transmission ground strap, add a supplemental strap, and clean the battery ground…

Before I crawl under the boxster, has anyone seen a bad engine ground strap cause this exact tach behavior on a 986? Anything else obvious I should check while I’m there?

Did this only start after you added the radio ground?

If this were an engine ground issue, you’d have way more going wrong. I’m fairly sure there’s a single lead that goes from the DME to the cluster for RPM signal. I don’t think adding engine ground is going to fix your issue, if anything it could be a DME ground but I think you would still have bigger issues.

Find the DME pinout for your specific car, and check the RPM signal wire for any continuity issues to start but I think the issue lies somewhere in what you’ve done with the radio.

1 points nickskater09

Did this only start after you added the radio ground?

If this were an engine ground issue, you’d have way more going wrong. I’m fairly sure there’s a single lead that goes from the DME to the cluster for RPM signal. I don’t think adding engine ground is going to fix your issue, if anything it could be a DME ground but I think you would still have bigger issues.

Find the DME pinout for your specific car, and check the RPM signal wire for any continuity issues to start but I think the issue lies somewhere in what you’ve done with the radio.