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Repair Questions and Answers.

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 #389022  by Puslecond

I'm in rather desperate need to find a replacement ABS-sensor (rear left) for my 2004 300M 2,7L Base.
The ABS-light and Trac off is lit, but there is no other problem with the brakes.
The issue (fault code) appeared shortly after a carwash and my guess is a stuck brake pad that somehow damaged the sensor with a loud "bonk", I did hear something get instuck, even though I never use the parkingbrake. I've since then replaced the parkingbrake pads and its related components.

This is the only fault on this otherwise loveable car with low milage and minumum wear, but with this fault I can not pass inspection and the car is now sadly in the "time out corner" in my garage.

I've been looking for months for OEM partnumber 4779155AB (or 4779155AA) without any luck, I have not even found a used one to buy.

So far I've been to three different mechanics to rule out any other source of the fault. All of them had an extra close look on the ABS-ring and found no issue. The sensor measures the correct Ohm over the pins and sends a signal when the wheel is rotated. I belive the signal is fluctuating for some reason. After resetting the faultcode, it comes back shortly after takeoff.

My question is: Is there hope or do I have to sell the car for scraps?

Best regards
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 #389023  by EasyRider300M
check your brake fluid level as a low level can cause the ABS light to come on. Happened to me. I added just a couple ounces of fluid and light turned off. Fluid level can drop due to brake linings wearing as was my case. Maybe you'll luck out and that will be the cause.
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 #389024  by FIREM
Sensor has correct ohms and sends a signal when the wheel is rotated tells us the sensor is OK.
Signal will vary with wheel speed however should be steady at a steady speed.
Check the tone ring carefully for rust making the teeth uneven and / or a crack causing an uneven gap between teeth. ( I had a front one crack causing a fault)
Play in the wheel bearing can also cause erratic signals.
If all is OK there then make sure the signal is getting all the way to the ABS unit (wire and connections all good.)
Make sure all ground connections are good. Hope this helps.
 #389030  by Puslecond
Thank you very much for your time and effort.

1. Brake fluid checked - OK level
2. Signal from sensor to connector pins was only detected using a simple Ohm meter. I need more proof if the signal is stable at a steady speed from a professional.
3. Tone ring was checked at all three workshops and no issue was found. This is a part fixed to the wheel bearing I'm told and we replaced this part at the third workshop with new bearing and tone ring. Issue remained, I conclude this can be ruled out aswell?
4. Checking the signal from sensor to ABS unit: I was told this was OK too but the third mechanic, but he was not an electrical expert with proper equipment.

I would assume the next step would be to turn to an electrical specialist and get absolute proof of the integrity of the electrical circuit, from sensor to ABS module to prove if the fault is electrical or mechanical.

I've found this on Youtube:

- Is this type of investigation the next step to take?

I'm still wondering what went "bonk" after the carwash and triggered the fault. Since I was not using the parking brake, could it be the regular brake pads getting unstuck and causing a mechanical deformation in the hub somewhere?
User avatar
 #389031  by FIREM
Road test with a data reader that can show each wheel speed sensor live data may be the only way to really find out what is going on.
Scannerdanner Rules! Great, accurate info in all his work
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 #389065  by hrmwrm
since the braking system will still work as normal, you can remove/disable the lights that are lit instead.
they'll only question a lit warning light.

knowing what the code is will tell you which one is the problem.
water and an intermittent signal will also cause failure to the computer.
as long as the plug is correct, the same type sensor from another corner or another chrysler vehicle with a similar sensor could probably be used.
as long as it the same sensor with just different cord lengths or mounting spots built in.