The title pretty much says it all. I have a manual mode switch code (P1815) and c1729 vehicle speed signal error code (i can't find anything on this online other than it's a vss error) There is no check engine light but i have noticed that my speedometer more often than not bounces a lot around and doesn't consistently read a speed. Like if i'm going 30mph consistently it will read around 30 and bounce above or below like something is going on with reading my speed. It also sometimes gets stuck right under 60mph not matter what speed i'm going and only read accurate again if i give it tap. I tried re soldering the instrument cluster and that actually fixed my fuel gauge problem but the bouncing still occurs. Not sure if my speed sensors have anything todo with it or if i just need to replace my entire cluster at this point. Thx for reading

 

You can verify the speed signal is correct by plugging in an OBD2 scanner that will show realtime speed data. Then you know that either the signal coming from the wheel speed sensors is correct, or it's not correct.

The wheel speed sensors for the speedometer are located at the rear differential. You might also get the car on jackstands and inspect them to make sure they aren't visibly damaged or the bolts have come loose or something. It's easy to see, right at the differential there are two "gear" looking things at the stub shafts that the CV axles bolt to, at the top on each side is a sensor that reads the gear. They attach to a single harness at the top rear of the diff.