onewhippedpuppy

2013 C300 sport 4Matic with 67k, started having intermittent ABS/traction/stability control faults that became very consistent. Multiple codes for implausible values on the right front ABS sensor so I replaced it. With the new sensor the car goes into limp mode, still showing the code for right front and front ABS sensors but now also adding 720 and 721 for implausible transmission output speed when compared to wheel speed sensors. Replaced the left front ABS sensor just to be comprehensive but the codes remain after reset and the car quickly goes into limp mode.

This seems like a pretty classic example of a 722.9 conductor plate failure, correct? Any other things I might be missing? Any recommendations for a shop to rebuild it? Looks like there are several options.

cvx5832

What brand wheel sensor did you install?

TimC300

^^^ Yes which brand were the replacement parts? Did you replace both sensors at the same time, or did you replace the front right sensor and were still getting codes so then replaced the left sensor?

What are the codes it is showing?

Which specific obd reader was used?

onewhippedpuppy

Bremi sensors, they were the only German made ones I could find on short notice. Replaced the right front first, had the first limp mode and still showed codes for the right front and front sensors so I replaced front left. Code reader is a higher end Autel from probably 8 years ago, the live data isn’t working so I have a Mercedes specific Launch Elite delivering today. I plan to clear everything with the new reader and go for a drive to see what triggers. I also want to make sure the wheel speed sensors are reading accurately using the live data.

Full code list: 0720, 0721, C11100,
C111200, C327100, C322200, 511100, 726600, 511200, 727100, 727300, 722300, C326600, C322300. Some of these my reader won’t decipher because they are Mercedes specific, so the new one should remedy that.

TimC300

I came across this thread. They mention using Bremi sensors and still had the issue, seems switching to Mercedes brand solved it.

https://mbworld.org/forums/m-class-w...ompatible.html

onewhippedpuppy

Well crap, that’s not very encouraging.

cvx5832

Not just Mercedes but in the BMW world, using off-brand sensors creates more problems than it solves.

onewhippedpuppy

I’ve been driving German cars almost exclusively for close to 30 years and always DIY, and can’t recall having a brand specific issue like this before. Before throwing any more parts at it, I’ll do an another scan and look at live data tonight.

cvx5832

Oil pressure and temp sensors (simple switches), sure. For anything ABS, camshaft/crankshaft sensors (hall effect), the output signal needs to be more precise, i.e. per MB spec. They're tougher to reverse-engineer for third part manufacturers.

onewhippedpuppy

Definitely see where it’s possible, just a new one for me. But these cars do always have a fun new way to screw me over.

cvx5832

Agreed!

JettaRed

iTrader: (1)

More encouraging than $2000+ for a new conductor plate installed. The 722.9 requires programming, as well.

onewhippedpuppy

Cleared codes with my snazzy new code reader and went for a drive. The ABS lights popped up immediately but it did not go into limp mode. Read the codes afterwards and all were for the right front wheel speed sensor. C003408, U140A, C111600, C111100, C327100. So I’ll try replacing the wheel speed sensors with OEM and report back.

onewhippedpuppy

Worth noting there are several companies that will rebuild your conductor plate for about $400, eliminating the need to reprogram the TCU. I did this with a G500 years ago.

JettaRed

iTrader: (1)

I have done that, as well, with my 2004 SL500. I used www.circuitboardmedics.com. But, they only fix the speed sensors (I believe) and not other problems you might have. I used them and the repaired conductor plate worked for a while. When I started having problems again, I took it to the dealer. Removal of the conductor plate is not particularly hard, but can be tricky on older cars because the connector sticks to the valve body. Go slow and gentle.

onewhippedpuppy

Closing this one out, it appears the OEM ABS wheel speed sensors have fixed the issue. To all the provided feedback, THANKS! Never would have guessed that as the issue.