andrewpaul

Hi my ML320 W164 was parked for 2 weeks in rainy humid weather. Now when I drive the car I get a grinding sound I think from the front Left wheel. The ESP yellow triangle comes on and the car cannot be driven. Feels like an ABS brake grab. I feel ABS as it is not a constant grab but a - brake - release - brake release l....

Just scanned the car with my basic Autel Scanner says Right Rear Speed Sensor Faulty strangely I get no ABS error code.

When I press the brake pedal it releases the grab for a second.

Any thoughts ideas? Is it the Right Rear sensor?

Thanks.... Andrew

Maj. Dundee

When car is setting for two weeks, rust will be formed on the rotor. Drive the veh. and apply brakes a number of times and the rust will disappear.

andrewpaul

Hi thanks for your reply this is definitely not a case of rusty rotors. I have experienced those. Here I can feel the car initiating the braking.

Maj. Dundee

Then you must read the codes in the ABS, ESP system. It could be the Yaw Rate Sensor.

andrewpaul

Thanks for the list will re-scan and compare the codes.

Question: as my ML is not drivable do you think a simple disconnect of the sensor would be advisable to let me locate the car back to my house garage for a proper inspection?

Also had re-scanned with live data from all 4 wheels and the Right Rear wheel sensor generates data but the speed is around half of the other wheels.

Thanks,

Andrew

Maj. Dundee

Remove the R/R wheel and brake rotor and you might possibly find that the parking brake shoe/s have dislodged .

DrDoe

Yours rear SAM got wet. Dry it out and all errors should go away.

andrewpaul

Sounds plausible Maj. Dundee will look into this.

Any thoughts on me unplugging the Speed Sensor?

andrewpaul

DrDoe inside the car is absolutely dry don't think the Rear SAM module could get wet.

DrDoe

I was driving with a 5 gallons water bottle in the back. It was rolling around and I didn't think much of it until I heard the sound of water gushing out of the bottle.
Pulled over and discarded about 4 gallons of water from the bottle and about 1 gallons of water from the weather mat. 1mile later, the triangle popped up with brake message then ABS and ESP. Continued to drive and the whole car shut down.
Parked in the sun with windows open for 1week and all errors went away.
That was my experience with brake error message.

Maj. Dundee

It won't correct the problem if the shoes cut loose, but try unplug.

andrewpaul

So finally got time and took the rotor off and there was nothing jamming just regular rotor dust which got cleaned.
My verdict was wrong I believe the jamming has something to do possibly with the ABS or transmission.
After cleaning the rotor the test drive was all good but I get the jamming all over again.
It is like the car is in Drive but Park mode has not released completely. Get this grinding vibration through the body.
When I press the brake pedal the jamming releases and things go normally for a few meters then jam again. Now and again the car drives as though nothing is wrong.

My assumptions on the little that I know:
- faulty ABS sensor - relaying a slower speed on one wheel and the braking is reacting - does that make sense to the experts? I have not unplugged the ABS wheel sensor that was relaying the slower speed.
- some issue in the 4matic Transmission?
- loose connection in the transmission - I remember being told by one tech that there is a connector in the transmission that should be replaced during my next transmission service. Make sense to anyone?
- A faulty solenoid in the transmission?

Any other thoughts or help?

Thanks.

chassis

Replace all four speed sensors to rule them out. From my reading of this thread, you are dabbling around at the edges of the problem. Time to throw parts at it.

How many miles do the brake pads and rotors have on them?

Is this vehicle is above-average, or below-average maintenance condition?

andrewpaul

Hi thanks for your response.

Brake pads and rotors are in good condition. Were replaced 18 months ago and have probably done max 25k kms since.

Car gets a regular 10k km service so pretty decently maintained.

The 4matic is due its 60k km service.

Car is 2006 and has 265k kms on it and I have never had the speed sensors done in my 115k km ownership.

chassis

Thanks. The suggestion to replace all speed sensors is still relevant in my view.

If the vehicle drives, then has a problem, it seems the problem is electrical/electronic. You have obtained error codes suggesting this, and you have suggested the vehicle is in at least average mechanical condition, so it's time to take action - replace the wheel speed sensors.

andrewpaul

Was a faulty rear speed sensor once replaced the problem disappeared.
Thanks for all your help and apologies for this delayed update.

Vmaxxer

I had exactly the same symptoms and in my case replacing 1 faulty ABS sensor was the solution