Thank you all MBDOC, WOLFGANG, ML 320, Azinn .......for all the advice

I have the 2002 ML 320 Km 136 000
Here is the problem I have not done much: mostly excuses being; 2 small kids and the fact that my ABS ETC etc and eventually the engine light sensor only comes on when it rains, further complicated by the fact that I just rust protected the vehicle underneath and on 2 occasion despite it raining the above sensor lights did not come (I assume the Rust proof agent acted as a waterproof for a while) I did take a visual observation under the vehicle looking for chaffed wires etc but must admit I could have been more thorough - I was shocked to find the one sensor right rear wheel disconnected ???? - remember the Snap-On "obd" reader gives PO 500 "A" indicating left side fault code (and yes MBDOC and Wolfgang said; take it to Merc so they can run a diagnostic on the proper Merc machine and I think he further stressed that they run scanner on the transmission sensor port), however, the ABS, ETS etc. and eventually the engine light sensor are back on again with the rain and will probably stop illuminating the dash when it dries up again.
But now I have an additional/further problem, doing a one direction 560 Km road trip I had no problem Averaging 125 km/h and using speed cruise control but on the return trip on a perfect dry road with he speed cruise control on the cruise control The Electronic traction stabilizer (ETS) started flashing (thereby automatically disengaging cruise control) and on one or two occasion felt a miss/hesitation, but it was not a engine, plug misfire. Under load or acceleration from 100 km/h and up, the ETS - Electronic traction stabilizer would flash intermittently - there where no other lights illuminated on the dash like when it rains, when I pulled into gas station radio off, window open, I felt and heard a intermittent rubbing/grabbing notice and sound from my left front wheel, upon a roadside visual inspection of rotor and pads for obstruction – none find.
My conclusion, Its not a wheel bearing causing the speed soensor to act up as there is no Whining noice eminating from and when I raised the front of the vehicle there was some play on both front wheels at 3 and 9 position, I assume now that there is a front left speed sensor or wiring problem from this point to the fusebox and is sending error code to the computer telling it that I am loosing traction on the front left wheel and braking as a result but I thought the ETS only engages up to 80 Km/h - if so must be real screwed up sensor

Conclusion I hope to do a better visual inspection for chaffing/short and remove Front left wheel and check under fuse box. And thanks to Nisan for you’re good advice OHM meter check on all three sensors remember the right rear one is disconeected - thank you
My reservation to follow MB DOC wolfgang ..... advice yet: is that it has been my suspicion that a wire/electric problem can take many hours and that the Technicians labour book does not specifically say how many hours, perhaps I should tel merc and find out how much it is to run diagnostics (presumably 1hr labour) and what’s the maximum labour that can be charged after that and lights only come on in rain.
So I think I am going to give it one more stab (do I wish I had the WIS or factory manual now !@#$~#$!#$%!) taking the above into consideration and IF I FAIL recognize defeat and call the MERCEDESE MINT Dealership

Click here
ABS/ETS/ESP Lights coming on

Something doesn't add up. If the wheel speed sensor is disconnected the ABS malfunction light should be lit up.

Those lights are a "free diagnostic" bundled with all MLs.

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Thanks for the post Wolfgang I will attempt to take a picture of the disconnection above and post same here just in case i have my sensors screwed up but if my memory serves me its the one next to the brake thickness/depth sensor.

What do u mean "free diagnostic"?

Thank you all those for their wonderful posts.
I found the problem some time ago - (sorry for the delay) on my ML 320. It happens to be the brake sensor wire chaffed and the wheel speed sensor wires chaffed behind the left rear wheel.
as the wires cross the left main frame and along the gas tank.
The first pic (specifically the corroded area) is the offending section.

Attached Thumbnails

   

I finally posted the pics above

Replaced battery in my 00' ML 320. BAC/ESP light stayed lit.
Thanks to RRodz for advice on how to re-activate the Steering Angle Sensor.

Cheers

Chris

Just to confirm, on my 99 ml320 the BAS and ETS lights came on and cruise would no longer engage.

Parked the ml in the Mercedes customer parking reached down popped out the switch (removed cover at home prior to heading to the dealer). Parts rep handed me the incorrect switch so I showed him the actual switch, he then handed me the correct switch (similar but different connector).

Paid $27 CDN for the switch. Walked out to vehicle rotated switch into place and started ml320. Voila, no fault lights and cruise works.

I assume that the switch was signalling the ECM that the brake was applied while roading so cruise will not engage and anti lock brake/stability systems react to the false signal from faulty switch.

No diagnostic$ required, thanks for posting the tip.

Mark L

Everything was going great given my repairs mentioned - no lights etc.
About mnth ago cruise control would not engage, replaced brake switch and all is good like a pig poo once again

I have already replaced brake switch and done reset procedure to no avail. BAS/ESP is still on and dealer says steering angle sensor needs to be replaced for $1500!

Does anyone have any other suggestions besides Vaseline?

Independent tech says no after-market alternative available.

Cheers,
Mark
2000 ML55 - 103K and still going.........

Silly question perhaps, but what is the Fault code and if so what does the code represent or indicate?

BAS/ESP, ETS, & ABS WARNING LIGHTS COME ON AFTER DRIVING A WHILE, I TURN IT OFF COOLS DOWN AND THEY GO OUT AN THEN AGAIN. I TOOK IT TO RUN A DIAGNOSIS & THE COOLANT TEMPERATURE SENSOR IS FAILING BUT IM NOT SURE THAT WILL WORK.

However, I am no rocket scientist and if I interpret 'generic' u mean that only MB diagnostic/code reader machine can provide the test and not a generic diagnostic/code reader machine and/or there is a specific machine to be plugged into the transmission/traction port - and this port is someone where else in the vehicle other than the port situated under the drivers dashport.
Or is it possible that the generic diagnostic/code reader machines give out diff codes numbers and letters to the Mb for the exact same problem

Other than issues related to emission (ODB2), a generic scanner won't find issues with the traction system.

A scanner must read traction system to diagnose that type of problem.

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