Restored My deactivated ADS (Kinda) - Mercedes-Benz Forum
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post #1 of 23 (permalink) Old 06-19-2019, 02:58 PM Thread Starter
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Restored My deactivated ADS (Kinda)

Ok, where to begin. Well I owned a 1991 500SL since 2007 now. The cars ADS was deactivated by a previous owner. After 12 long years I finally restored the system back in the car. It wasn't cheap nor easy, and I've yet to enjoy it as it has a MIL ADS dash light on

I bought a lot of components new, such as shocks, springs, spheres, all the main hoses that run from the pump to the tank to each individual shock absorber. I bought some items second hand from scrap yards such as front and rear valves and some hydraulic lines.

Upon installation, the dash light came on and it gave me DTC 5 Steering angle sensor. There was no angle sensor on my car as my steering wheel was updated to the 96-98 AMG model. I looked up several topics here and used ilcats.ru to get the correct part numbers and hunted for cars with ADS on the scrap yard. After installing humorous Steering Angle Sensors, I always get the DTC 14 Steering Angle Not Activated/initialized. I tried full left lock full right lock and nothing happens at all. The steering angle part number I got was 0085429517 it was from a 91 500SL with ADS, I even got the horn contact plate from the same car, still nothing.

After various attempts, I decided to try the 96-02 steering angle sensor, part number 0005426418. I had to change the steering angle sensor black plug/bracket and airbag plug/bracket to fit my car. I used the ones from the other period correct SAS. Did a full lock left and right turns and viola!!! It works, the light went off. Or so I thought.

Well the light did go off but only for like 10 seconds, it came back one and now it stays on permanently, as in it's on as soon as I turn on the ignition. The DTC is 4 though, which is wheel acceleration sensor. I can't seem to be able to delete this code, it is permanently on. I bought two sensors from the scrap yard for dirt cheap but they didn't work. One of them managed to kill the MIL light for like 5 seconds but it came back on.

Now I'm stuck looking for wheel acceleration sensors in the scrap yard. They all seem in such crap shape, new ones are like 800$. Did anyone have a similar situation like this, or did anyone attempt to fix one of these sensors. I know they are very sensitive to shock it seems

Sorry for the long post, I hope the forum doesn't format it without paragraphs as I noticed that this tends to happen when posting on my phone.
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post #2 of 23 (permalink) Old 06-19-2019, 06:56 PM
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Code 4 does not indicate a faulty wheel acceleration sensor per se. Wiring and the ADS controller could also be at fault, and that's what I would look at. Refer to the diagnostic manual for guidance: STAR TekInfo.
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post #3 of 23 (permalink) Old 06-20-2019, 12:42 AM Thread Starter
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Thanks for the link Bobterry, I tested the connection using a voltmeter of the ABS harness where the wheel acceleration sensor connects and also from the harness to the N51 module. It seemed fine

I also swapped in a used ADS module in place of N51 and the light did go out but only for a few seconds. It came back on and gave me the same DTC 4 reading. I tried switching back and forth between my original N51 module and the spare one but nothing happened, the light stay on no matter what.

So i returned the module and kept mine, thinking it's probably the wheel acceleration sensor.
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post #4 of 23 (permalink) Old 06-24-2019, 11:29 AM Thread Starter
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Code 4 does not indicate a faulty wheel acceleration sensor per se. Wiring and the ADS controller could also be at fault, and that's what I would look at. Refer to the diagnostic manual for guidance: STAR TekInfo.
Bobterry I went to the scrap yard today and tried two different ADS computer modules N51. Upon plugging them in I still have the ADS dash MIL light, but now it's giving me DTC 13 Oil Level switch instead of DTC 4 wheel acceleration sensor! Both of them.

When I switch my own ADS module back in it gives me DTC 4 wheel acceleration sensor. Does that mean my module is bad? Also please note I tried another module previously that managed to kill the light for a few seconds the first time but came back on with DTC 4 wheel acceleration sensor.

The weird thing about these codes is that they are not erasable and that while reading them they give you no other errors whatsoever. The same thing happened with the steering angle sensor, however when I was trying sensors, the car would start for a couple of seconds with the MIL light out and then come on. And there were no other codes than the steering angle sensor back then as well. The wheel acceleration sensor started to give me an error only when I installed the 96+ SAS which cleared that fault.

It's weird that you have to fix each fault to see the next one, that doesn't make sense. Specially that when my rear dampening actuators were disconnected I was able to read them normally and along with other codes and fix them respectively.

What do you think? Is it an ADS N51 module or wheel acceleration sensor or oil level switch?

Appreciate your help
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post #5 of 23 (permalink) Old 06-24-2019, 11:56 AM
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There was a reason the previous owner decided to kill the ADS on this car! Ask to all the M120 owners how many headaches they had trying to fix their stock ADS...
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post #6 of 23 (permalink) Old 06-24-2019, 02:05 PM Thread Starter
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There was a reason the previous owner decided to kill the ADS on this car! Ask to all the M120 owners how many headaches they had trying to fix their stock ADS...
Not really, the previous owner was a cheap bastard who rather delete anything or take shortcuts than fix it properly. Anyways that's besides the point.

I just need to pin this electrical fault down to one thing and fix it up.
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post #7 of 23 (permalink) Old 06-24-2019, 02:58 PM
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Is it an ADS N51 module or wheel acceleration sensor or oil level switch?
The odds say your N51 is bad, but you can eliminate the uncertainty by checking the oil level sensor with a basic multimeter. See the diagnostic manual instructions for troubleshooting code "13". (If the sensor is bad the resistance across it measured at its connector or the N51 connector is less than 500 ohms).
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post #8 of 23 (permalink) Old 06-25-2019, 11:31 AM Thread Starter
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Originally Posted by AG129 View Post
Is it an ADS N51 module or wheel acceleration sensor or oil level switch?
The odds say your N51 is bad, but you can eliminate the uncertainty by checking the oil level sensor with a basic multimeter. See the diagnostic manual instructions for troubleshooting code "13". (If the sensor is bad the resistance across it measured at its connector or the N51 connector is less than 500 ohms).
Here's an update.

I switched the N51 module with the one that was giving me DTC 13 oil level switch. I check the wires of the oil level switch and they were brittle, upon cutting and placing new plugs on the wires I was able to delete the DTC 13.

Switched on the car and the light went out for a few seconds but came back on. I read the codes again, it gave me DTC 14 steering angle sensor not initialized/activated. I did the full lock left and right multiple times and it gave me DTC 5 Steering angle sensor instead.

I noticed that if you disconnected the SAS it will still give you DTC 5. So DTC 5 is the N51 module not reading the SAS at all. The SAS installed on my car is the 96+ model year version which shouldn't work on my ADS I car. I'm thinking of trying the 91 SAS versions that I tried before, maybe it would initialize with the new N51 module. With the old module all the old version SAS were giving me DTC 14 SAS not activated, and weren't resetting with the full lock method.

Maybe it would work this time with the different N51 module.

Bobterry, the new 96+ steering angle sensor part number 0005426418 shouldn't work on my 91 model year right?
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post #9 of 23 (permalink) Old 06-25-2019, 11:49 AM
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My guess is that the later steering angle sensor will work with your car.

I would test. Unplug the electrical connector to the ADS controller and with the key on measure the voltage between its connector sockets #21 and #23. Measure both AC and DC voltage and report back with a description of what you measured.

If the sockets aren't numbered and the identity of the above sockets as ambiguous, then know that #21 is wired to a green wire and #23 to a brown wire.
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post #10 of 23 (permalink) Old 06-26-2019, 11:00 AM Thread Starter
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My guess is that the later steering angle sensor will work with your car.

I would test. Unplug the electrical connector to the ADS controller and with the key on measure the voltage between its connector sockets #21 and #23. Measure both AC and DC voltage and report back with a description of what you measured.

If the sockets aren't numbered and the identity of the above sockets as ambiguous, then know that #21 is wired to a green wire and #23 to a brown wire.
Hey Bobterry, sorry I took some time as I didn't have access to a multimeter, got one now.

I measured ad you said between pins 21 and 23 in the ADS module connector, I got the following

DCV = 7.28
ACV = 5.28

Does that sound right so far?
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