2001 ML320

2 months ago I was driving down a straight road doing 45 mph when all of a sudden the front breaks locked up by them selves. I took it to the local mechanic that say it was probably the break light switch as the cruise control stopped working as well.

I had them replace the break light switch and all 4 breaks as they were almost due anyway. Everything seemed fine for 2 months when all of a sudden the breaks locked up again doing about 30 mpg on a straight road. When trying to drive the breaks would lock up again as soon as I passed the 1000 rpm mark. I had the car towed and the mechanic got 2 codes:

C1120 B24/15 (Rotary speed and lateral acceleration sensor): Signal cable has Open circuit or Short circuit. (FAULT INDICATOR LAMP ON)
C1120 B24/15 (Rotary speed and lateral acceleration sensor): Signal cable has Open circuit or Short circuit. (STORED)

They checked all the wires and there were no shorts. They then went ahead and replaced the Lateral Accelerometer 163-542-06-18. I picked up the car drove about 20 miles before the breaks locked up again and the BAS light came on. I was able to get into a parking lot by keeping the car below 1000 rpm. After turning the car off for a few minutes I was able to drive another 5 miles home without the breaks engaging on their own.

The codes that show are the same as before. What else could cause this? A yaw sensor?

Have the mechanic take the truck for a test drive or go for a test drive with you.

Gilly

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C1120 is a code for the YAW rate sensor, NOT the lateral acceleration sensor.

They replaced the WRONG part.

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Is the YAW sensor a plug and play part or does it need to be reprogrammed/tuned by a Mercedes computer?

99% of the time plug & play.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Craziness. Neither the yaw rate sensor or the lateral accel. sensor would/should cause the brakes to lock up.
Over the past four months we (Portland) have had two early ML's (98' and 99' 320's) lock up the front wheels. The front rotors were scorched. The front calipers got so hot the calipers could not be pushed back so we had to replace front calipers pads and rotors. As a precautionary we replaced the master cylinders due to theories of over heating damage. But both vehicles had ABS pumps installed as per Mercedes Benz.

How's this for a scenario:
Pads are being replaced by numbskulls or with inferior pads without the replacement caliper bracket slider pieces (that the MB pads come with on these). So the original slider pieces are wearing out and causing the pads to stick out a little, causing drag on the rotor, which builds up heat, which causes the brake fluid to expand, causing even more drag, until the brake locks up. Which is why you had toruble getting the piston back in to remove this mess. I believe the fluid expanding would affect both front brakes.
They had a similar problem with the rear brakes on the 220 chassis when it first came out, but was caused by a dragging parking brake.
Gilly

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Replacing the lateral accelerometer did not make a difference. The car would lock the breaks again after a few miles of driving.

I went ahead and replaced the YAW rate sensor and have not had any problems with the breaks engaging by themselves again. Have not seen any ABS/ETS lights come on either.

Since I have driven close so a 1000 miles since replacing the YAW rate sensor and everything has been working great I think it is safe to say that at least in my case the breaking was caused by a faulty YAW rate sensor. Both parts were very easy to replace by yourself.

Thanks for all the help in getting this resolved!

I have a ML320 with 98000 and I had the brakes replaced about 10000 miles ago (cost $1000 not from ML). I do not use the vehicle very often and the following issue recently started.
The brakes locked up on a 15mile drive to the office. I drove it home with this condition but the brakes got very hot. After I got home the smell of brake burning pads was very strong. Both front wheels were so hot that they could burn the skin from you hand if you touched them.
I have not driven the car sense. How do I fix this issue?

Hi Henrik, I'm have a similar wheel locking issue with my 2001 ML320. While taking a turn the outer wheel tries to lock up and makes a sound as if ABS was kicking in on the outer wheel. I am planning to replace the YAW rate sensor so I have a few questions if you could answer for me.
- Did you replace the YAW rate sensor yourself and was it easy to replace?
- Did you take any pictures while doing it and if yes could you please share them with me?
- Where did you buy the YAW rate sensor and how much did it cost?
Waiting for you reply.
Thanks in advance
Gurdeep