amgmooch

Hello mbworld first of all I searched threads all over but I can't find exact info I need I have a 2000 clk430 vert after getting new tires the brake light cel visit workshop so I stop by autozone and scanned got codes for p0500 which is vss vehicle speed sensor and p0720 vehicle speed output

It's causing my car not to shift and high rpms and speedmotor at 0

But what's weird at first start up it drives normal then all lights come on then the symptoms I described happens again then I shut off then again and drive normal for 5 mins or so then same symptoms

Ima great diyer and worked at BMW shop as helper for a year so I'm not scared to do my own repairs so I can help out too if I can

I hate electrical work by the way

MarcusF

A clearer answer follows -

MarcusF

The short answer is, it may be the tires. If not, possibly a speed sensor.

The longer answer is the logic behind how your speedo works is built around the rolling diameter of your front and rear tires being very close. To calculate vehicle speed, the instrument cluster computer checks the wheel speed of all four wheel speed sensors. The instrument cluster receives the wheel speeds in RPM from the traction system. The individual wheel speeds are compared and checked for plausibility (for example; do the speed sensors indicate three wheels spinning at 80 MPH and one at 20 MPH?). If wheel speed signals differ significantly, you will have issues. If no significant differences in individual wheel speed signals are found, the left front wheel is used to establish vehicle speed. Since your issues started as soon as you got the tires, lets start there. Please post the exact tire make and sizes that you had installed, front and rear. If it's not the tires, a speed sensor may be damaged.

BTW a P0500 is a partial message. The P0500 means either a 20CA (the left rear wheel speed sensor isn't sending a signal) or a 20CB (the left front wheel speed sensor isn't sending a signal). If it's not the tires, a shot of compressed air and possibly some brake cleaner may used to clean the left side wheel sensors. I'd wear a mask.

raa

I have the same problem after changing tires original size (f-225-45/17, r-245-40/17) & new wheel size Im putting on. (f-245-35/18, r-285-35/18. My question is there anything I can do (recalibrate?) to run these new tires. Or do I have to stay with original tire size all the time. In other words I can't change wheels and tires on this vehicle.

insame1

your sidewall height should not be the same front to back read the post above yours.

Serndipity

Make sure that the rolling circumference of your new tires must be within a small percentage of the OE tire circumference(s)..

There are numerous 'tire size calculators' online to help you determine this.

insame1

Really the OE tire circumference isn't that important if you dont care about the speedo. Having them differ front to back will screw up the traction control.

2MERKS

Wow, 285 rears!

ctravis595

That’s really weird.. I recently had a tcu tune done, it took some extra hours to set things up over Star because my I have a Cl55 engine and e55 transmission in my cl500. Once we got the new tcu working it was pretty cool, faster shifts, new M mode etc

but there was some uncertainty within the transmission around 35mph, it was like it couldn’t tell whether it wanted 3rd/4th or 5th gear when cruising. Or perhaps like the torque converter was locking and unlocking over and over..

anyways. Yesterday I was driving spiritedly (as usual) and my cruise control and speedometer all shut off at once at about 65 mph...Soon after the car would get stuck in either 3rd or 5th gear until I restarted the car. This happened twice over the span of about 2 hours. Eventually it set a p0720 code

today I drove the car for many hours, no returning p0720 code strangely enough. I decided to look up p0720 and I came across this thread...

then i remembered two days ago I got two new (used) rear tires! And I went with 255/30/20’s instead of 275/35/30 because they were cheap. I’m starting To wonder if the car has “adapted” to the new tires... although I’m not in disbelief that I may need a new conductor plate sooner than later... hope this helps someone else who gets new tire sizes and a p0720 code

markayash

I bought new factory size tires and had weird issues..Scary when driving in the mountains and ABS and traction stuff goes off..I could usually stop, turn car on and off and back to normal..Replaced Uniroyal with Generals and problem was gone..I now wonder if they had a 245 on front and visa versa..Tires also wore out in about 8000 miles

ctravis595

unfortunately my p720 came back one time, ive driven the car a lot since my last post

seems my conductor plate may be on its way out