1997 C280 Trouble
 

1997 c280
Limp home mode. ABS and check engine light. Ran an OBD-II check which came back with:
P0500 Vehicle Speed Sensor Malfunction
P0720 Output Speed Sensor Circuit Malfunction

No chassis code (c1100-3) given.

I would guess that means the VSS on the differential is bad?
Any input would be appreciated.

Thanks

You can test the speed sensor by measuring resistance and AC output voltage.

Check resistance while tugging speed sensor wire.
Check AC output while rotating tire.

Vin

I've seen the diff sensor bad. Keep in mind it also uses the one in the tranny if your car is late enough production to have a .6 tranny. (easy to spot, W-S switch on the shifter)



If your scanner is able to read it, check actual valves for the rear speed sensor readings.


Joe

Very common failure & easy repair! Just replace the ABS speed sensor in the Diff. MB part number 202-540-26-17, we do this about once a week on the 1996 & later cars.

For the record it was the sensor on the diff. The AC output was nil so I got the replacement and checked the resistance vs the original and it was way out of wack. Pulling it out was a bit of a pain-- it snapped off where the steel sleeve ends. Then the guts came out w/o the steel sleeve. Used an angled drill bit powered by pliers to finally pull the sleeve.
New one went in, buttoned everything up. Check engine cleared on startup, ABS by the end of the driveway.

Thanks to all that replied.

I had the same problem, and fix. The CE light still on though.
 

Hi. I recently experienced the exact same problem, with the same symptoms, in my '97 C280 (105K mi).

Replacing the rear speed sensor (part 202-540-26-17) immediately remedied the problem. The car now shifts smoothly, and the ABS light went out as soon as soon as it went into 2nd gear. However, the check engine light did not go off for about ten miles.