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97 SL500, 98 E320 Wagon, 2002 ML500 - former W108/W112/W114/W123/W124/W126/W140/W220
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Discussion Starter #1 (Edited)
Sorry to do this, but I've spent the better part of the weekend researching my issues and found little to nothing that corresponds with other threads for similar warnings. So bear with me and I'll do my best to present everything as best i can.

As a preface, I'm a 30 year Mercedes owner and a former high-line mechanic, so my diagnostic skills are probably at the higher end of the scale. I have a STAR/DAS system so I can access codes, faults and see active data as required.

So why could this be so darned perplexing????

Here's the deal:

2002 ML500
195k

Complaint:

BAS comes on randomly. Can often clear it with the "lock to lock" steering wheel turning. Will often come on maybe 10-15 miles later.

BAS/ESP/ETS/ABS will come on as a group, accompanied by the "Brake" warning light. This is accompanied by the peeping alarm that continues to sound as long as the car is moving. Come to a stop, lights remain on, peeping stops.

Running a full scan using the DAS system, the only faults that come up are C1140 (steering angle sensor) and C1306 (right rear axle solenoid valve).

ABS pump has been checked and it runs by doing an activation though DAS.

Voltage tests as prescribed in Star Tekinfo for the steering angle sensor are correct. Looking at actual values for the steering angle sensor in DAS reflect correct values. Steering has been zeroed and cleared both using DAS and with the "lock to lock" method as well.

Car was aligned recently (again, steering is centered properly and the steering angle sensor reflects this) and I have the same tires with lots of tread all the way around.

I replaced the brake light switch and installed it per the bulletin, as I had one on the shelf.

I suspect I'm looking at multiple issues here possibly, and this is why I say this:

I replaced a right rear caliper last week. I bled the system with my pressure bleeder, but the first time I put my foot on the brake pedal it went to the floor. Once it returned I had pedal, but the travel seemed long and if I maintain pressure on the pedal it will leak down very slowly. It's also spongy.

I'm wondering if when the pedal went to the floor the cups in the master cylinder might have been damaged. Based on this I'm pretty sure I need to replace the master cylinder.

Differential pressures at the master cylinder were checked in DAS and they're right on the money, so I don't see where that would cause an issue, but the leaking down can't be anything but the master cylinder. However, if that was leading to some of these alarms why doesn't it occur when the brakes are applied rather than just coming up as what appears to be random intervals?

The only other thing I can think of to toss into the mix is that the ECU box blower is not working. Totally dead, I've got a replacement coming later this week. I'm also wondering if it would be wise to disconnect the battery, disconnect all the modules in the ECU box and clean the connectors with contact cleaner.

And a proverbial red herring:

No horn. Fuses are good, horns are good. I've wondered if someone has been into the steering column and messed with the clock spring and/or things in that neighborhood. I'm not getting any error codes for airbags or anything like that, however.

I'm open to any and all suggestions at this point. I'm practically stumped.

Thanks,

Dan
 

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2004 ML500,Sport; 2014 ML550; 2009 ACURA TSX
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Check transmission code. It’s likely that one of the speed sensor on the wheel is bad. I had the same issue last month, case was bad left wheel sensor. P2403 code was stored.

photo attached.
 

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97 SL500, 98 E320 Wagon, 2002 ML500 - former W108/W112/W114/W123/W124/W126/W140/W220
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6,252 Posts
Discussion Starter #3
Check transmission code. It’s likely that one of the speed sensor on the wheel is bad. I had the same issue last month, case was bad left wheel sensor. P2403 code was stored.
Thanks, I'll look into that. I don't recall having any transmission error codes, but I'll run a check tomorrow and see.

Dan
 

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2000 ML55 sold😢 2013 ML500,😁 2015 C250 estate wagon, 1927 Dodge 4 sedan, 1929 Dodge
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Swap relay 25 with one similar and check the brushes in the ABS motor.
You still have a couple of other issues but that’s a start.


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97 SL500, 98 E320 Wagon, 2002 ML500 - former W108/W112/W114/W123/W124/W126/W140/W220
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Discussion Starter #5
Swap relay 25 with one similar and check the brushes in the ABS motor.
You still have a couple of other issues but that’s a start.


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I've got some new relays on the way, as a couple of them appear to be slightly discolored as if they've overheated. I'll swap relay 25 this afternoon after work.

I've run the diagnostics on the ABS pump and it runs fine and without any noise to speak of, so I'm going to assume the brushes are fine. I can pull it if necessary (I've got the windshield washer reservoir out at present) but since it checks out in DAS OK I'm reluctant to be pulling it apart.

I found a bulletin last night that talks about corrosion on the ESP module connector which causes random errors, so I'm planning on disconnecting the battery and cleaning connectors in the ECU box later today.

Thanks for the suggestions, and keep them coming!

Dan
 

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2000 ML55 sold😢 2013 ML500,😁 2015 C250 estate wagon, 1927 Dodge 4 sedan, 1929 Dodge
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Also have a look at the ABS control unit connection, it is prone to corrosion from leaking water washer reservoir.
Pull the left hand inner fender and trace the ABS loom along and make sure it hasn’t rubbed through to bare wires along the length of it.


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97 SL500, 98 E320 Wagon, 2002 ML500 - former W108/W112/W114/W123/W124/W126/W140/W220
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Discussion Starter #7
Thanks again for the suggestions!

As I’ve read through darned near every thread on these issues, I’ve seen this referenced as well. I inspected the ABS harness this past weekend and found no damage, the windshield washer reservoir does not appear to have been leaking, and I disconnected the connector at the ABS module and hosed it down with contact cleaner.

Dan
 

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Dallas, Texas
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BAS/ESP/ETS/ABS will come on as a group, accompanied by the "Brake" warning light. This is accompanied by the peeping alarm that continues to sound as long as the car is moving. Come to a stop, lights remain on, peeping stops.
For this issue drive around while watching live data for parking brake switch and brake fluid level switch.

Similar issue.
https://www.benzworld.org/forums/w163-m-class/3024078-2002-ml500-intermittent-mysterious-beeping-brake.html?highlight=brake+fluid

https://www.benzworld.org/forums/w163-m-class/3024758-brake-master-cylinder-reservoir-sensor-part.html?highlight=brake+fluid
 

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97 SL500, 98 E320 Wagon, 2002 ML500 - former W108/W112/W114/W123/W124/W126/W140/W220
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Discussion Starter #9
Thanks a bunch!

Trying to sift through this and separate all the various fault is a real challenge at times. I’m wondering if I’ll see any fault codes related to this when I scan it tonight? I’ll report back what I find.

Again, thanks!
 

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2002 W163 ML400 CDi
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While you replace the ECU fan go through every connector you can find in the box. Literally pull out every cable you can.
The box leaks....
There are a few connectors buried right at the very bottom, and I found a few cruddy ones so cleaned the lot up while it was apart (I was actually looking for the brake pad sensor connectors).
Probably not your issue but worth eliminating while you are there.
 

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97 SL500, 98 E320 Wagon, 2002 ML500 - former W108/W112/W114/W123/W124/W126/W140/W220
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Discussion Starter #11 (Edited)
UPDATE

So I ran a full set of diagnostics on the car this afternoon. I haven't touched a thing since Sunday, so this is with all of the warning lights described having occurred and ideally being in fault memory.

Of all the systems, the only faults that came up were for the steering angle sensor not being initialized.

C1140 - 007 - Steering angle sensor N49
C1140 - 008 - Steering angle sensor N49 Not initialised
C1140 - 010 - Steering angle sensor N49 Code error

There was also a C1300 - 016 Solenoid valve FL A7/3y6 Hold pressure

I'm assuming this is totally unrelated to my steering angle sensor issue.

Hopefully these will add some context to what I'm experiencing, although based on prior information in the thread it certainly sounds like I'm dealing with multiple issues.

On that same subject relative to the brake warning light, since I believe the parking brake switch to be good, couldn't I disconnect one or both of the brake fluid level sensor leads to take it out of the circuit? I'm assuming it's a purely analog device (switch) so if it's open circuit and my parking brake switch is good, I shouldn't see the brake warning light again if the brake fluid level sender is at fault.

Just looking for validation of my logic here....

Thanks again,

Dan
 

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Discussion Starter #12
Cleaned connectors in apparatus box last night and cleared codes.

Drove to work this morning, about 20 miles of half surface streets and half highway. BAS light came on as I was pulling into my parking space. No other lights.

I’m thinking about cleaning the connector and the steering angle sensor in case they’re cruddy for whatever reason. Can’t hurt, I guess.

Dan
 

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Coupe/Convertible Forums Moderator
CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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The problem with the horn combined with the steering angle sensor losing its calibration leads me to believe it is a bad clockspring.
 

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Discussion Starter #14
The problem with the horn combined with the steering angle sensor losing its calibration leads me to believe it is a bad clockspring.
And you know, that's been in the back of my mind as well. However, I don't see the clock spring coming into play as the steering angle sensor does all the position sensing as far as I am aware.

If that's not the case I certainly would like to know. I would definitely pull the steering wheel and see what's up in that area if necessary.

I just can't help but wonder if something is disconnected in the steering wheel or the clock spring is damaged somehow, which could potentially manifest itself as a horn problem.

Hmm....

Thanks!

Dan
 

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CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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I'm not sure about the implementation in the W163, bit on other models, the clockspring and steering angle position sensor are all in one unit. When installing it, there is a specific alignment procedure and if not followed, it can cause intermittent faults and problems with the steering wheel components (since the ML lacks radio/menu buttons, just its horn).
 

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97 SL500, 98 E320 Wagon, 2002 ML500 - former W108/W112/W114/W123/W124/W126/W140/W220
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Discussion Starter #16
I'm not sure about the implementation in the W163, bit on other models, the clockspring and steering angle position sensor are all in one unit. When installing it, there is a specific alignment procedure and if not followed, it can cause intermittent faults and problems with the steering wheel components (since the ML lacks radio/menu buttons, just its horn).
They are separate on the W163. The steering angle sensor is located on the steering shaft about halfway between the steering wheel and the firewall, just ahead of a universal joint in the shaft. If you pull the panel under the driver's side dash it's just above the brake pedal or thereabouts.

Your logic is similar to mine, however, as I'm familiar with the clock spring and it's functions in other models, such as the W140 and W210 chassis cars.

I may still pop the airbag off this weekend and have a look to see if something is up with the horn wiring...

Dan
 

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Make sure SAS has clean power supply from circuit 30 and 15. I have seen trailer brake controller wired to it.:eek
 

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Discussion Starter #18
Will do.

I’m going to crawl under the dash this evening and give the SAS and the connector a good cleaning with some contact cleaner. Can’t hurt, and maybe it’s just a matter of some corrosion.

I would add that this car had sat unused for over a year when I bought it. Being that I’m in Florida there’s a good chance of cruddy connections.

Thanks.

Dan
 

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Discussion Starter #19
Got sidetracked today, as the battery in the car puked yesterday.

Got that dealt with, then went and replaced the right side motor mount, all of the spark plugs on the right side, and installed a new motor in the apparatus case fan.

Tomorrow I'm going to tackle the left side motor mount and spark plugs, not looking forward to that due to the limited amount of space available to work in. I started with the right side as a confidence builder, as I routinely do with any MB V8 car.

Also took the time to get the battery cover sorted and the coolant circulating pump back where it belongs on the battery cover. The PO had just left it hanging in the engine compartment....

When I started up after battery replacement I got the obligatory BAS light, but the lock to lock with the steering wheel made it go out. I'm still planning on crawling under the dash and hosing the steering angle sensor down with some contact cleaner along with the connector.

I can see light at the end of the tunnel - I think. I'm wondering if the bad battery was causing some of my warning light weirdness...

Dan
 

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I'm wondering if the bad battery was causing some of my warning light weirdness...

Dan
Stable power supply is the key. No dips on startup, no alternator going over 15V trying to recharge the brick.
 
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