Nimeral

2011 ML63 Cold Start Electrical Issue Saga

Hi All,

This is my first post. My dealer recently solved a very tricky cold start electrical issue on my 2011 ML63 AMG and figured I should do a writeup to help someone diagnose the same problem in the future.

TLDR version: odd cold start behavior (low battery voltage, many warning lights, wipers on without any rain, refuse to shift out of park, and engine refused to start after the first attempt) after parked overnight in -15C to -20C temperatures. Dealer diagnosed it as a faulty ignition switch.

I’m the second owner. The first owner purchased it in October 2010 near Vancouver, and I assume it lived its life down there until I purchased it. It only had 44,000km when I bought it, and Mercedes Benz Kamloops informed me the previous owner had it serviced at Mercedes dealers every year until they sold it

I live in Kamloops BC which has a much colder climate than Vancouver. The issue started this winter at about 49,000km. It was probably its first time experiencing real winter temperatures, so who knows how long the issue had been around. It sleeps in my heated garage at home, so it had not been exposed to seriously cold temperatures overnight until I was parked outside this past Christmas.

First time:

December 26th and 27th 2017: ML63 was parked outside for 2 days without being used with the temperature at about -20C. I needed to use it, so I started it up and went back inside to let it warm up. Upon returning to the vehicle after 5-10 minutes, it was behaving oddly:
- Wipers on (it was not raining or snowing)
- ESP warning
- ABS warning
- Airbag warning
- SRS restraint system warning
- Possibly also a check engine light, though I’m not certain
- Battery voltage was 14V with engine running, but 11V when off, so the battery was indeed low
- Would not shift out of park: not into drive, neutral, or reverse

I then turned it off and attempted to restart, but it refused to try and turn over. It was not a “dead battery” type start, it was not engaging the starter motor at all, like it was locked out. I tried both with the key in my pocket, and the key in the dash. Neither worked.

I tried to jump start it with one of the in-laws vehicles and same behavior, it refused to try to start even with proper battery voltage.

The next day I tried starting it and it behaved like it had a dead battery: when it the starter motor kicked in, all the interior and dash lights blinked out for a second. I then hooked it up to another vehicle and let it charge for 10 minutes or so. Lo and behold, it started without any issues!

I took it in to Mercedes Benz Kamloops the next day. All the codes were related to low voltage, so they checked the battery and it was indicating it needed a charge and did not need to be replaced. Given the $500 cost of an ML battery, I had them charge it for me. Surprising given the battery was the original from 2010.

My first guess at the cause? The REST system that keeps the car warm when its parked for up to 30 minutes. I’m pretty sure I’ve observed it running much longer than 30 minutes in my garage. It could’

Second time:

January 1st, 2018: ML parked outside overnight, approximately -16 or -18C. Same issue in the morning: the car started, but soon after starting it displayed many warnings and would not shift out of park. Letting it idle for 15 minutes did not clear any codes, still would not shift. After turning it off, it would not restart. I tried jumping it again, and it would not start, same lockout behavior, it wasn’t even trying.

As I was parked on a street where they charge for parking and I didn’t have the time to try and screw with it the next day, I had it towed to Mercedes Benz Kamloops. I had them replace the battery, as the one in the car was the original and was about 7 years old. I thought this would solve it….but I was wrong!

Third time:

Middle of February 2018: parked overnight at a cabin, low of -18 or -20C overnight. Same issue in the morning with all the same symptoms except the battery was not low. Started but would not shift, then would not restart. Had it towed to Mercedes Benz Kamloops again. Side note: it’s not fun watching a tow truck operator drag your AWD vehicle onto a flat deck with it locked in park. Unfortunately he did not have wheel dolleys. It hurt to watch.

This time I intended to leave the ML with the dealer until they diagnosed the issue. Thankfully the dealer is 5 minutes from home, and 5 minutes from work.

After scanning codes, they found all the same low voltage errors, with the addition of a CAN bus communications problem. Unfortunately, I was told CAN bus errors get saved with only some details, not enough to pinpoint where the problem was. If they could scan it while the issue was active, they can pinpoint it exactly. But do you think the ML would act up in their possession? Nope!

I had their tech make his best guess and spend a couple hours of labour to inspect common CAN bus connector locations where there are issues: under the driver’s seat, and inside the rear bumper. Both were clean, no corrosion.

I left it with them for a week, as the forecast was for cold temps each night. Each morning they would go start it up and it would behave normally, no issues. After a week and a half the issue had not surfaced and I was racking up diagnostic time. I chatted with their service advisor and their service manager and we decided to leave it for one last cold night. They were as stumped as I was and sympathized with my frustration.

We decided to do things a bit differently for the last attempt: we parked it facing downhill (this was common between all three incidents, and hey why not try it), with the smart key close by (so the car could sense it), and they would open and close the doors and rear hatch before locking it at the end of the day. It was forecast for about -17C that night.

Eureka!

In the morning, they started it up and moved it to a different parking spot. When they went back to check it, BAM, the issue was active! The car would not restart and would not shift out of park. I’m not sure in what order this all took place, but they scanned it, moved it into their service bay, and found the problem: the ignition switch. It was in an active fault state, and was not letting the ML start or shift. It was actually stuck in their service bay; they couldn’t move it! Lucky me J

The part took 2 days to arrive and the issue cleared when they installed it. Both keys obviously had to be re-synced to it.

I haven’t had a chance to leave it overnight in cold temperatures since, so it’s hard to be 100% confident the problem has been solved. But if the ignition switch was faulting, that part was obviously no good and certainly would have contributed to the problem.

Mercedes-Benz Kamloops was good to me. The service coordinator kept me informed of any updates. They gave me a loaner car for almost two weeks (my choice of a B-class, GLA, or C-class) with real winter tires. And before the problem was fixed, they were willing to eat most of the diagnostic labour since they had no result. Once it was fixed they understandably wanted to recoup their costs.

Final bill: ~10 hours of diagnostic time + ignition switch ($900) + installation labour = ~$2300. My third party warranty paid 4 hours of diagnostic time, the part, and the installation labour, minus my $250 deductible. I paid their deductible plus 6 hours of labour, so about $1,100. Warranty paid ~$1,200.

Oh and plus two tows: one in town, one about an hours drive. Not cheap!

Hope this helps someone in the future. I will update if the issue rears its head again.

Adam.

Ed954

Thanks for sharing!