Leaderboard

Thank you for the explanation. I was thinking the ribs were the 5 indentations vertically along the vehicle (looking from the top of the vehicle). Makes a lot more sense now.

Since my van is an XL, it doesn't have a digital speed display, aside from the cruise control setting (I even had to add the CC, dealer-ordered van with just power locks/windows only). But, I have a ScanGuage II hooked up and the analog speedometer matches the SGII pretty well 99% of the time, sometimes they'll be off by 1MPH from each other but even that is pretty rare.

Yes. Speed is calculated from tire size and number of revolutions. This data bit is sent to the IPC on the MS CAN and displayed. There is no resolution loss or calibration needed. Any calibration is done in the tire size data field. I did some research and also took apart the original IPC. The only adjustment you can make on the analog speedo is to change the starting point of the pointer. This is very tedious and requires disassembling the unit. Basically you carefully note the current ) mph position and determine how far it needs to move. Pry off the needle without changing it's position and reinstall in the new location. The shaft on the needle is not keyed. The IPC will reset the needle to the 0 mph position every key cycle. If your speed error increases with speed I have not found any way to fix or adjust this.