Spooky55

My car has recently become nearly undriveable due to codes P0720 Output Speed Sensor Circuit and P0600 Serial Communication Link. The trans goes into limp mode and won't shift from second gear, the speedometer drops to zero and I get "Brake wear visit workshop" and "Display malfunction visit workshop" as well as an ABS light on my dash. If I shut the engine off and restart, it will USUALLY clear and I can drive a short way until it comes up again.

Where do I start? Should I be looking at the speed sensors, the ABS module, or maybe a transmission conductor plate?

Robjr

Spooky55......

Did you scan with a good OBDII scanner? Start there as that should give you an idea of where to go next. It could be a number of issues with the four (4) speed sensors located on the knuckle right behind the caliper. It could also be a bad ground wire contact on the ABS module which wire attaches to the front left fender under the hood. Remove it and wire brush and exchange the old washer with a new one. A bad spark plug wire connection can also triger a P0720 dtc.

Here's a url with some MBWorld forum answers that can possibly help solve your issues.

https://mbworld.org/forums/c32-amg-c...ion-issue.html

Keep this forum posted as to what you find out.

Good luck....

Rob

Spooky55

I just used OBD Fusion on my phone. I have iCarsoft MB 2.0 and STAR, but STAR is a PITA to deal with and MB 2.0 is SLOW.

I checked all the plug wires and reseated them snugly. I had just replaced plugs on Cyl #6 about 2-300 miles ago due to fouling and had the wires reversed (top to rear plug instead of front), so I switched them. Removed the ground strap near the ABS unit and took a wire brush to it.

Drove about 8 miles with no problems. If it comes back, I'll update the thread (and use a better scanner) with any additional codes.

Thank you!

deep4k

A bad spark plug wire can really cause a p0720? I’m having a similar issue with my car. 2013 c350 coupe 4matic. I was driving on the highway cruising at 70mph and out of nowhere the car stopped accelerating/responding to the pedal. I pull over and shut it off and it’ll go into each gear no issue (shown by the dash and my scanner) but just revs regardless of the gear. The only code I have is for the transmission P0720 no esp/abs/trac faults. I thought maybe the fluid was low and flushed that out and dropped the pan but everything looked good. Still the same issue anfter a refill. Any help is appreciated.

cdk4219

I would first check the transmission electrical plug for fluid intrusion, then the conductor plate is the next suspect