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'00 ML 430
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Discussion Starter #1
I guess at some point in the ownership of a W163 one inevitably gets confronted with the dreaded BAS/ESP light. In my case it was an interesting couple of episodes a couple of years back where the truck at some point would randomly "think" it was in a skid and apply brakes. Scary as hell when this happens at highway speeds. These episodes happened a couple of year back, once going up a pass and once driving at highway speeds. At the time the C3 identified the yaw sensor as faulty. However, I somehow didn't pull the trigger and nothing happened for years. I cleared the codes and all was well.

Fast forward to a couple of weeks back where the dreaded BAS/ESP light came on again. First it was intermittent but after a week it stayed on through cycling the ignition. I whipped out the C3 again. And sure it was the yaw sensor failure again. This time I looked at actual values. With the sensor in "failed" condition it read read a steady rate of turn of +8.5 - 9.0 deg/sec with the vehicle stationary. The correct reading is something like 0.2 - 0.5 deg/sec.

A quick review of the schematic showed the signal to the sensor is three wires: power, GND, and yaw signal. This makes this puppy an analog sensor. Most likely it puts out 0V - 5V for - 90deg/sec - +90deg/sec turn ratio with 0deg turn rate being at 2.5V. When you disconnect it the reading is pegged at 90 deg/sec. There are only two connectors in the signal path: One at the sensor and the other at the ESP module. I disconnected both and cleaned both with a good contact cleaning spray. After that the reading return to almost zero. I believe the cleaning has addressed the issue. I reset the adaptation values and went through a driving test cycle. It completed without errors.

Let's hope the cleaning has addressed the issue for at least another couple of years.
 

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w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
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I heard of similar issues where the wiring (harness) up front (behind the d/s headlamp assembly) has rubbed against the metal and right thru the wire insulation causing a short and "christmas lights" on the bas/esp. Cant move the shifter, etc. Had to isolate the bare wires on the harness hoping to correct it.
Bonus for you only needing to clean the contacts. Those units are $$$$.

:)
 

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2000 Mercedes Benz ML320
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This time I looked at actual values. With the sensor in "failed" condition it read read a steady rate of turn of +8.5 - 9.0 deg/sec with the vehicle stationary. The correct reading is something like 0.2 - 0.5 deg/sec.

A quick review of the schematic showed the signal to the sensor is three wires: power, GND, and yaw signal. This makes this puppy an analog sensor.
You've got the C1120 DTC? Any C1000?

There is a "reference voltage" of approx 5V (4.75 to 5.25) provided by the ESP CU to the sensor. The sensor signal depends on the "reference voltage".

The ESP CU is configured the sensor signal "zero point variation" and the "angle/turning variation". One potential cause for C1120 DTC is the ESP CU detecting a sensor signal being "out of range" of the configured values. The "out of range" can be a deviation caused by a "reference voltage" being out of range.

The most likely culprit for the "deviation" of the "reference voltage" is - besides aged electronic components, and sensor - the overheating of the ESP CU. The running at higher than normal temperature is caused most likely by the failure of the F1 Box Cooling Fan. The cooling fan is activated by a 12V/4700 rpm DC motor on which the brushes get worn in time, and the motor quits working.

Have you checked the F1 Box Cooling Fan?

There are a number of threads/posts on this topic, with the most recent one providing info about a DC motor that has a very close RPM to the spec 4700 rpm. I've posted myself about installing a higher RPM motor and lowering the RPM to 4700rpm by using power resistors in series.

Most likely it puts out 0V - 5V for - 90deg/sec - +90deg/sec turn ratio with 0deg turn rate being at 2.5V. When you disconnect it the reading is pegged at 90 deg/sec.
Have you measured the signal voltage?

If you're curious to see the signal variation, along with other ESP sensor signals variations, see this post and illustration #4:

https://www.benzworld.org/forums/17473747-post27.html

There are only two connectors in the signal path: One at the sensor and the other at the ESP module. I disconnected both and cleaned both with a good contact cleaning spray. After that the reading return to almost zero. I believe the cleaning has addressed the issue. I reset the adaptation values and went through a driving test cycle. It completed without errors.
The ESP adaptation has reconfigured the "zero point variation" and "turning variation" for both the Yaw Rate and Lateral Acceleration Sensors, which is the best way to proceed.

Well done!
mercbentz
 

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Discussion Starter #4
Crap: wife reports BAS/ESP is back intermittently after a long drive. That would fit the overheating theory. I’ll check the fan motor in the fuse box. Unfortunately I’m not gonna get to this for weeks due to other commitments.

Great data in your thread/post. What are the units on the graph for steering angle and yaw rate sensor? mV relativ to 2.5V reference?

I will have to hook up my handheld o-scope and compare raw voltages (sensor supply and signal) to the reported angular value in HHT to determine where the error is. It’s either the sensor or the control module. Both seem reasonably affordable used from evil bay. Maybe worth an attempt.
 

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Crap: wife reports BAS/ESP is back intermittently after a long drive. That would fit the overheating theory. I’ll check the fan motor in the fuse box. Unfortunately I’m not gonna get to this for weeks due to other commitments.

Great data in your thread/post. What are the units on the graph for steering angle and yaw rate sensor? mV relativ to 2.5V reference?

I will have to hook up my handheld o-scope and compare raw voltages (sensor supply and signal) to the reported angular value in HHT to determine where the error is. It’s either the sensor or the control module. Both seem reasonably affordable used from evil bay. Maybe worth an attempt.
Usually, if the fan moves, there is a tiny winning sound that can be heard after switching the engine OFF. I believe on your car the ESP and ME2-SFI CUs share the heat...

In retrospect, I should have measured the ESP CU 5V source before replacing the fan motor in two instances: (1) right after engine start, when temperature was at minimum and (2) then after a longer trip, when engine and F1 Box were at highest temperature... I could disconnect the fan and still do it, for research purpose...
....
The units on the graph for the SAS and YRS are "degree" (left axis), respectively "degree/sec" (right axis) as resulted from the Autel scanner Live Data collection.

The graphs show a "BAS/ESP light ON" problem diagnostics in progress.

I would be curious to see voltage measurements/graphs.

mercbentz
 

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94 S420 RIP 2/8/13 02 ML55AMG, 06 CLS55AMG, 89 Mas. 228, 84 Por. 911 Carrera, 93 Toyota t.t. Supra
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You don’t say what mileage is on your truck but my ML55 had 130k on it and I discovered that my recirc pump was silent. In fact the entire engine compartment was silent after key was off. Not a good thing on this truck. No check engine light or other irregularities but I replaced the circ pump and opened up the fuse box and low and behold no fan operation. Replaced that and now when you shut her down she sounds like she’s humming. Those electrical parts deteriorate with heat from the engine and age as well as usage. Would suggest you replace the fan unless it’s going (which depending on your mileage it may not be) and then check the circ pump. It generally stays on for 5 min more or less after the engine is shut down and makes a distinctive hum and if you put your hand on it you will feel it vibrate. Good luck.
 

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Open up the fusebox to check the E-Box fan. The fan is 99.9% likely dead. Even if you find the fan still running, replace it.

It's not the heat or age that kills the fan, rather accumulated dust on fan blade put too much stress to fan motor. Some folks clean & reuse the fan but you'll need a new motor.

Photo below was taken on my ML320 in Mar 2013, about 160,000 miles.
 

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Discussion Starter #9
@mercbentz: do you have a higher resolution graph of your data? If your units are really +/- 90 deg for the yaw sensor it would read about -25 deg in a straight line? That’s sound wrong. Mine is less than a degree when stationary.
@Noodles: I replaced the circ pump a couple of years ago with the cheap alternative (believe VW or similar) At that time I cleaned the fan and re-lubed the e-box fan motor and it was fine. But it could be bad again. Need to check and if stalled will drop the one in you mentioned. It’s still selling on evil bay.
 

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do you have a higher resolution graph of your data? If your units are really +/- 90 deg for the yaw sensor it would read about -25 deg in a straight line? That’s sound wrong. Mine is less than a degree when stationary.
Your observation is correct, the static - no car motion - variation should be around and close to zero - i.e. horizontal axis.

As indicated, the graph is an example of a diagnostics purpose live data collection. It shows a "deviated zero point variation range". If I recall correctly, the variation is small, but above the zero horizontal axis. Which can be interpreted that possibly an ESP Adaptation would have reconfigured the CU's sensor static range and eliminate the deviation - signal delivered relative to the reference voltage received from the CU - and worked well afterwards.

Need to check and if stalled will drop the one in you mentioned. It’s still selling on evil bay.
In my experience, the Igarashi motors from Ebay - spring of 2018 - even though specified at 4500rpm, delivered only about 4100 rpm at 12V - measured with digital tachometer - and the seller could not make a correction, and thus accepted a return at no cost to the buyer.

Consequently I installed a higher RPM motor, which resistors in series, which deliver 4700rpm - measured with digital tachometer.

Since then, a source was posted on the Forum, for 5000rpm/12V, which I've got, and which deliver about 4800 rpm at 12V, but have not installed yet, as current solution works just fine.

mercbentz
 

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Discussion Starter #11 (Edited)
Can you direct me to the post with the fan motor source? I searched but came up empty. Thanks

Never mind - found it.
 

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You will be pleased. It takes all of 20 minutes to do.

I had found the Parbst fans at mouser.com for $50, but they are now discontinued by Mouser.
 

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Discussion Starter #13
Here is an update on my BAS/ESP light situation:

Over the last three weeks while I was gone the car showed a scary and consistent behavior: About 30 minutes to 1 hour into a drive with outside temperatures around 75F - 85F the ESP system would suddenly engage out of the blue and try to get the car out of an imaginary spin. The yellow triangle indicates a spin/slip and the brakes kick in. Once that happens and the ignition is cycled the ESP light remains on. Subsequent driving is fine with no more episodes.

After the car sits for several hour or overnight the ESP light remains off after engine start and the car is ready for another episode. Additionally as explained in my first post when the ESP light remains on the fault in the ESP module is the yaw sensor and its actual value is a turn rate of around 9 - 10 deg/sec while the car is stationary.

To me this is consistent with my current theory that the temperature in the fuse box goes up over time and causes the ESP module to mis-interpret the yaw sensor signal. Others referred to a reference voltage going to the sensor. This is actually the +5V power supply to the yaw sensor. The sensor receives GND and +5V power and reports back with an analog signal between 0V and 5V where +2.5V corresponds to 0 deg/sec turn rate. My guess is that with raising temperature either the +5V supply jumps to another level or the A/D converter reading the yaw signal "jumps" To really drill down on this I would have to put a data logger onto the +5V and the yaw signal and at the same time log real time data. Too involved at this point.

Today I removed the e-box fan and sure enough observed the hamster wheel was only spinning lazily and not moving much air at all. Speed varied whether it was pointing sideways or downwards. That's a sure sign for a shot motor bearing. I was in that fan about 4 years ago. At that time I lubed the bearings, cleaned everything and called it quits. If I remember correctly that also was the time when the ESP acted up. So it is entirely conceivable that this slowly dying fan motor is the culprit (again).

I replaced the motor with the Nichibo QJT-360S-14280 12 Volt DC Motor from Jameco. The swap took about 15 minutes and now the fan wheel spins much more vigorously and moves a significant amount of air. My plan is to observe this for a couple of weeks to see if and how the behavior changes.

Just in case I also acquired a replacement ESP module and another used yaw sensor. If the ESP episodes continue I will replace the yaw sensor next and then the ESP module. I can't think of anything else - stay tuned.
 

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Hey guys:

I think my ML has a dead fuse / relay box cooling fan.

I hear nothing spinning / feel no vibration with "key on".

Ok I found fan in rearmost corner of box.

Its quite buried under wire bundles, etc. So much so, I can't see all of it.

Does it only run at higher temps ?

I did see Google images it is pretty big.

How exactly does this fan assembly remove ?

Thx for your help !

Thx - David
 

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Discussion Starter #16
There are two gold-colored metal tabs that hold the black plastic fan housing down. By pulling on the housing and pushing back on those tabs you’ll get it out.

On the ML the fan motor and the cooling recirculating pump spin as soon as the ignition is turned on and continue about 2 minutes after the key is removed.

If the cooling recirculating pump is seized it probably fries the fuse. A stalled fan doesn’t pull enough amps to do that.
 

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Thanks to you both for the help, 43 & PCar !

And I also surmise you have to gently move wires out of the way, as well.

I am super curious to see if motor can be resurrected at all. We can call it Lazarus if it works, right ?

Now it appears totally dead, no noise or movement under any condition.

I plan to de-gunk it with my can of electrical cleaner in & out + the plastic fan blade.

I guess for $7 it makes sense to order the Amazon motor & have on hand to solder into place if this one cannot be made functional again.

Good to know it should work for 2 minutes after key off.

Is the same timer used for BOTH coolant recirc pump & this fan ? Regardless of temperature ?

Thanks a ton for the help !

David In East Texas

PS:

I'll update things on my progress.

I did resurrect that other thread: "DIY E-Box Fan Repair"

It may be more to the point to put my update over there, right ?
 

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Discussion Starter #18
Don’t bother. It’ll last a couple of months and will fail again. Ask me how I know. Put a new one in while you’re at it.

Both motors run on the same circuit so their timing is the same.
 

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....

I am super curious to see if motor can be resurrected at all. We can call it Lazarus if it works, right ?

Now it appears totally dead, no noise or movement under any condition.

I plan to de-gunk it with my can of electrical cleaner in & out + the plastic fan blade.
Cleaning the fan, and enclosure is a must. But when it comes to the motor, cleaning will not do much.

It is a DC motor, so the brushes are most likely completely worn out. The large amount of black dust/debris is from the brushes. Cleaning is not going to restore the brushes. Replacing with new brushes requires finding and ordering the right ones. It is a lot cheaper to order a new motor. Make sure the motor spins at or close to RPM=4700.

mercbentz
 

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Great input guys - thanks so much.

Per your joint testimony I'll simply order that correct motor from Amazon & solder it onto the harness / enclosure, along with cleaning fan blade.

No point cleaning it if its toast.

I though motor rpm should be in =4700 range, correct ?

David
 
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