mikedr

Here's a new one. 2014 GLK, less than 800 miles. Today, after driving the car 15 minutes, I get two warnings at the exact same time from the car -- pre-safe functions limited, and front airbag service required (with airbag light).

Can anyone think of a reason why both would come on at the exact same time? Problem happened three times over a period of a few hours. The pre-safe I understand could be due to a dirty sensor (although the car is and has been clean), but it's suspicious to me that I'm getting that warning at the exact same time the front airbag service required.

I can clear out both messages by pressing OK, but the airbag light stays on until I stop the car. Starting up the next time, everything's OK again for 10-15 minutes.

Will be calling the dealer Monday morning, but figured I'd ask to see if anyone else has seen this before.

koalatm

Anything unusual happening with the front passenger seat? ie: a dog on the seat, or something along those lines? Could mess with the airbag sensor for sure.

mikedr

We think we found an answer -- a Mercedes tech on another site indicated that when both come up together, the reason why is that the airbag sensor is bad, and when the airbag sensor goes, presafe doesn't work . . . .

mikedr

Update, he said/she said. Dealer says it's the seat guys wiring of the ventilated seats. Seat guy says he didn't touch the airbag sensor, and there's nothing different than can do. Sigh. So no we have no front passenger airbag. I'm at a loss as to what I should do other than trade it in and eat the $35k loss.

ble2716

Ouch.
No wonder why nobody wants to mess with their car when it's still under warranty.
Even though the upgrade/mod were not even related to the cause.

Did you even ask the dealer if it is repairable? and how much it will cost?
If possible, ask for a written estimate.

mikedr

Dealer says it's a wiring issue. Still think it's the sensor. They want $2k to replace it. We're going on a 24 hour road trip in the Death Trap (my new nickname for our glk), and will go to an Indy shop where we summer to get a second opinion. Otherwise, we're trading it in. At a loss of $30-40k sadly.

mikedr

Looking at a Porsche Macan Turbo.

koalatm

This is the process I'd follow:

• Get the part number(s) of the part(s) the dealer thinks are defective.
• Get a quote from the parts department at a different dealer.
• Determine where the sensor is located. If it's in the seat, I'd say the guy that did your ventilated seats should take some of the responsibility and help you out.

It is worth pointing out to your dealer that the Magnuson-Moss warranty act in your country provides you with a great deal of protection regarding warrantable issues. They cannot under any circumstance void your complete warranty. If any after market mods are interfering with the sensor, they have a case... if these are completely unrelated, they need to do the work.

Quite frankly, the dealer should want to do the work - warranty work pays better than regular work as they can bill shop time based on the prescribed warranty process, and normally most service folks can do the work a lot quicker than the shop times listed in service manuals.

fabbrisd1

The dealer is sortof "hog tied" - from a liability standpoint - if I understand correctly owner had a upolstery "shop" modify both front seats to "add" ventilation" - which is a modification that the dealer is not equipped or authorized by MB to do.

Yes, modification of the front seat can impact the seat sensor, and in this case the factory wiring harness I "believe" will not have proper connections, so wiring to add that mod is outside/separate from MB wiring harness.

For the dealer - big time liability issue that frankly Mercedes will not allow the dealer to dive into.

bytemaster0

Agreed. To add the ventilation, the installer likely used the existing seat wiring harnesses. I bet the seat belt connector also goes through this harness. The car is either now improperly wired, or is sensing a different load condition and throwing an error, as it should. I'm also inclined to think that the seat mods have everything to do with this issue. I highly doubt that the airbag sensor itself is faulty; the system just thinks this is the case, as it's a symptom of a greater problem due to new wiring causing electrical issues with the seat systems, possibly seat belt or something else related to SRS, such as the passenger weight sensor. Change the seats back to spec, and this error might resolve itself.

mikedr

Thank you all for your input! It's been very informative. I did a bunch of other research on this issue, too. What follows is the email I sent to my seat guy and my dealer rep as to my proposed plan to solve this issue. I would definitely welcome everyone's thoughts here as well!!

-----

In terms of "escalation," I'm thinking of proceeding in this way:

(1) I'll bring the car in (again, sadly, not for a while), and you can inspect all the connections, perhaps reconnect all the connections under the seat where they interface with the harness, and even unplug and plug the airbag sensor in again. I read one guy who had an older Mercedes that was having a problem like ours, and he simply disconnected the connector, blew into it, reconnected it, and the problem went away! That is, the issue could be as simple as there being a sufficiently poor connection somewhere that is causing the problem.

In this respect, today I'm going to shine a flashlight under the seat just to make sure that none of the wires look "crimped" or bent in a weird way. The one thing I'm having trouble figuring out is why this problem first manifested itself two weeks after having the seat work done. The only thing we could think of is that since the work has been done, the passenger seat wasn't moved after the first day until this past weekend -- Sherry took a friend out to dinner who moved the seat, and then when Sherry and I were driving the next day she moved the seat up and back. It wasn't until after that happened, when I was driving alone, that the problem first started. So I'm hoping (!) that perhaps the issue is as simply as the harness got stuck in a rail or something. I do know a few days beforehand when I was going through the car I saw some wiring harnesses, and pushed them back in.

(2) If this does not work, my next plan is to have you rewire the car back to "stock" in terms of the passenger seat. That is, you would disconnect the heating/ventilation controls from the passenger seat harness completely. Then, you would run new power lines, completely divorced from the seat harness, to power the heating/ventilation -- perhaps from the driver side harness, where there is no such occupancy sensor.

The idea here is that from an electrical perspective, there would be nothing different from the computer to the passenger seat than there was before the problem showed up. All the power for the heating/ventilation controls would come from a different harness/line. In theory, then, whatever electrical load (voltage, resistive, capacitive, inductive) that simply wiring the controls into the passenger harness would go away, and everything would work.

(3) Nevertheless, if this does not work, I have one last "hail mary" option. The thinking is that if (2) doesn't work, then the problem is that the physical addition of the heating and ventilation elements in the passenger seat itself is affecting the occupancy sensor, which is a resistive pad that changes electrical response in accordance with passenger weight. Third parties sell "occupancy sensor emulators." You disconnect the occupancy sensor, and connect the emulator in its place. This then tricks the computer into thinking that someone is always sitting in the passenger seat; you can't have a child seat or a dog in the passenger seat (although I'm openly wondering if some sort of switch could be connected inline), but it removes any interaction from the heating and ventilation elements with the occupancy sensor as a potential cause of this problem.

Apparently people buy such emulators primarily when they have older cars, and the occupancy sensors go bad. The sensors cost a lot, and this is a cheaper solution that still ensures proper airbag operation, with the downside noted above. Again, this is the hail mary option -- my preference would be not to have to go this route. I'm very much hoping that (1) will do the trick, and that we wouldn't have to proceed past (2).

mikedr

Update. First, the problem manifested itself two weeks after the seat work was done, which I thought was odd, since if the seats were the problem, then in theory the problem should've shown up sooner.

In any case, after a passenger sat in the seat since the problem appeared, the problem has since gone away after multiple starts. Keeping my fingers crossed that it was just a strange gremlin issue.