Hello, my Saab has developed an issue whereby the speedo gets stuck 30/40/50+ miles an hour and rev counter sits at 3500+ at idle.

I have seen some other posts about this but none exactly the same.

Things I have noticed, even though the speedo is reading 130mph and I am doing only 70mph ish (via GPS) the speed alarm I configured will still sound at 75mph (135 on speedo) - so some of the cars brain knows what the real speed is.

There are no ABS warning lights and cruise control continues to work as expected.

Disconnecting the battery or removing the fuse will reset the issue for a while but it seems to come back quicker with this wet weather we've been having.

I understand there is some sort of speed sensor in the left hand rear hub - anyone got a pic of what it looks like or a part number? Are there other speed sensors to look for?

I have heard there is some sort of ECU for speed sensor? Where is this located?

Any tips for troubleshooting / identifying the issue would be great.