I disabled the Auto Start/Stop function shortly after acquiring my G550 4 years ago, by disconnecting the battery sensor output signal at the battery's negative terminal. This makes the ECU think the battery's charge state can't support restarts, and so Auto Start/Stop gets disabled. *** is apparently the only purpose this battery sensor has -- disconnecting it never triggered the CEL or caused a DTC that was detected by my Topdon AD600 OBD scanner. I upgraded to an AD900BT scanner a couple months ago when Topdon was doing a year end promotion. The AD900BT runs a much deeper scan, and reported 2 DTCs -- U113E00 and U113E87 -- both related to communication with the battery sensor. I confirmed this by reconnecting the battery sensor, clearing the DTCs and running another scan -- these codes were definitely a consequence of the disconnected sensor. But despite these codes, I never experienced any problems. If *** had ever suddenly stopped working by itself, these DTC's would have identified one possible failure.

The AD900BT includes among its 28 maintenance services the ability to code the Auto Start/Stop function OFF, so I did this today. I reconnected the sensor and took the truck for a 10 mile drive to let the engine warm up and to top the battery charge, both pre-requisites for the Auto Start/Stop to do its deed. I had forgotten how really annoying Auto Start/Stop is. Then I used the AD900BT to do the coding, and it did the job -- took the truck for another drive will several stops. Each time I stopped the "circle arrow A" icon appeared on the instrument panel, indicative of the function being disabled, while the engine continued running. Back home, I ran another scan with the battery sensor connected and the Auto Start/Stop coded OFF, and the previously reported DTCs did not show up. Although there's no difference in vehicle behavior, coding the function off seems much less a hack.

The AD900BT also includes tire size coding, but unfortunately Mercedes is not included among the brands covered. This is an annoyance among all the brands of OBDII scanners. They all boast about the number of vehicle maintenance services they provide, and more services are provided as the scanner price increases. But not all services can be performed on all car brands, so what you get is like Forest Gump's box of chocolates. My AD600 has oil reset, but not for Mercedes. My AD900BT says Mercedes is included in its oil reset, so I'll find out in another 3K miles.

 

This was informative. Thanks for posting your experience.

Regarding the tire size coding, is that just coding the tire size into your car should you ever change to a different tire size? So then the speed might also change based on revolutions per mile on the new tire size?

 

Yes -- changing the effective diameter so that the speedo and odo are accurate. I mounted 275/55R20's in place of the OE 275/50R20's that result in about 3% error, and would like to correct this.

 

I guess the shift points would probably change too. I'll have to check if my Creader scan tool allows this.

Update: @streborx I wasn't able to figure out how to change the tire sizes on the Launch C-Reader but @S-Prihadi did. Here's his post on how to do it with the Launch brand scan tool.

 

Just purchased this Launch scanner (it was sale priced last week for $149), which features auto start/stop disable, and enough other coding options to get you in trouble. Also scans and sends printed reports. It's the best scanner I now own.

 

Awesome! Did you update your tire circumference successfully, too?

 

I found the tire circumference settings buried deep in the PTCU menu. Still trying to sort out the selections and how best to determine before and after speedo readings. Will follow up with full report when implemented.

 

Looking forward to seeing your results! I’ve been putting off ordering 275/55 tires and was going to this year; The timing of these two threads couldn’t be more perfect.

 

I've been running 275/55R20's for 20K miles without any problems. Maybe correcting a 3% error is being **** -- mostly I'm just curious about how it can be done.

 

@streborx thanks for the recommendation. I picked up a Launch scanner and was able to disable start/stop on my 2018. Same price as a Mid City dongle and you get a whole scanner on top! I saw the tire size could be changed but haven't experimented with that yet.

 

Can this device be used to activate ILS too?

 

Starting a new thread on the tire circumference topic.

 

I may be wrong on this but I don't believe the 2018 has the necessary headlights for ILS so I don't know.

 

Heads up for folks that have the Launch reader and care about data privacy… all your reports get stored to their cloud with no way I’ve found to delete them. It also persisted after doing a device reset. I assume more data gets snarfed, too.

Here’s the test I ran:
1. Set up device (I used a separate temporary WiFi network), skipped all the ‘shop customization’ info since i figured that would get saved on their servers.
2. SW updated all the modules
3. Disconnected from Wifi.
4. Ran a report with my car. (I suspected at this point it would try to send data to servers, which is why I disconnected from Wifi)
5. Later on in the day I connected to Wifi again and noticed in Settings that my previous report is now in the Cloud tab when you look at data. You can delete the local reports, but you cannot delete the Cloud reports.
6. Performed a complete device reset, and looked in Settings; Cloud data is still present which means it’s likely simply keyed with the device serial number. So if you ever sell or give the device away, it looks like the next owner will still have access to your data (and of course, whoever has access to the server data).

This won’t stop me from using the device and I assume anything network connected is taking, unfortunately, some data, but it does support my thinking that now that I’ve got the SW modules updated this will stay off network and if I ever need to update SW modules again all local data is going to be deleted before it goes back on. Right now I gave up my vehicle’s VIN and whatever data is in that report; Not the worst, but I’m glad I didn’t add any personal information anywhere in the device.

The next test for me is to see if I can change just my temperature units to °C, since the settings in Command are basically an all or nothing Metric or US customary units (and I don’t want the car in km and km/h, just inside / outside temp in °C)