Electrical Problem - Mercedes GLA Forums
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post #1 of 11 (permalink) Old 07-28-2015, 03:36 PM Thread Starter
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Anybody experienced anything like this...Yesterday I couldn't unlock my GLA, no response from either keyfob so I tried the physical key to unlock the door. This unlocked the door but didn't unlock the central locking or deactivate the alarm which went off. I tried the fob in the dash and was presented with a display full of warning lights and error messages. The engine wouldn't start, or even turn over. Couldn't find anything in the manual, so I called recovery. As promised over the phone, an engineer turned up after a couple of hours. I didn't see everything he tried, but he did charge the battery (although he said that wasn't the fault). He also checked the error logs (he said there were a lot, but nothing to cause this), he'reset' the ECU by shortingthe battery terminals (battery disconnected) and exercised the electrical connections on the ECU. He was then able to lock/unlock the doors, deactivating the alarm and central locking. He was then able the change gear and disengage and engage the parking brake. This was important as it meant the car could be recovered. He re-seated a couple of relays in the fusebox (in the passenger footwell). The car still would not start.He arranged for the car to be recovered, secured over night (as it waslate)and transported to the dealer.The dealer called me today to let me know the car was ready for me to collect. They said there were no error logs showing and asked If I'd had any work done asa couple of relays were installed incorrectly. I told them the engineer had pulled some relays and he had reset the ECU which was presumably why no errors were logged. Either way, when the relays were refitted, the car started.Assuming the engineer mis-fitted the relays (It was dark any wet when he was here, he may not have refitted them correctly) and besides, the problem was alreadypresent.I don't believe any problem was found and as such it may recur. It's alsopossible it isa one off. Time will tell.
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post #2 of 11 (permalink) Old 07-28-2015, 05:00 PM
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Generally speaking, relays are designed so that they can only be fitted one way: the correct way! As for the rest, the car's brain (CPU, ECU, EMU, whatever) clearly had a fit, probably caused by some software bug that is only triggered once in a blue moon. A total (proper) reset would have fixed it, in the same way as a Windoze PC needs to be switched off and on every now and then. Given the amount of testing these cars get, I would expect this to be a very rare problem.




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post #3 of 11 (permalink) Old 07-28-2015, 06:29 PM Thread Starter
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I thought the same about relays, though I didn't see the specific ones. Maybe the person on the phone meant 'they were not fully installed' rather than 'the wrong way round' which is what they said. Either way, I don't think that was the cause, something would have happened earlier. I'm hoping it's a 'once in a blue moon' thing, though I'll be a bit apprehensive for a while, when pressing the unlock button.It's a pity thelog waswiped in the attempted fix.At least I know the recovery does it's job.
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post #4 of 11 (permalink) Old 07-28-2015, 08:22 PM
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I doubt if the standard logging mechanisms would have stored the kind of in-depth error messaging that would have been useful for a software engineer to properly understand what caused the main CPU to go doolally (that's a technical term, similar to 'throwing a wobbly'). That degree of error logging can usually be enabled, but it fills up the logs pretty quickly, so is normally only enabled when you know you've got a recurring problem that is likely to go again soon. This level of fault-finding and fixing would be beyond the capabilities of dealership mechanics/engineers, so in summary then: I doubt if the vehicles logs would have helped.




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post #5 of 11 (permalink) Old 07-29-2015, 02:22 AM Thread Starter
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Well it wasn't a one off, it's dead again this morning.
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post #6 of 11 (permalink) Old 07-29-2015, 05:40 AM
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...at least they'll have something more to get their diagnostic teeth into now then. If something has failed again that soon then it is indicative of an unserviceable component or a loose connection or broken wire, all of which are 5000% easier to find and fix than a software bug.




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post #7 of 11 (permalink) Old 07-29-2015, 01:09 PM Thread Starter
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An they should have an intact set of error logs
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post #8 of 11 (permalink) Old 07-31-2015, 11:25 AM Thread Starter
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I had an update from the dealer this morning.They have concluded that the ignition switch is faulty and have a replacement one on backorder from Germany. Could be up to 2 weeks.I'm just glad they were able to find something. Hopefully that will fix it.
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post #9 of 11 (permalink) Old 07-31-2015, 11:43 AM
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Fingers crossed




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post #10 of 11 (permalink) Old 10-07-2015, 02:17 PM Thread Starter
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Just to update anyone interested...

The part (EIS module) arrived after only a couple of days, rather than 2 weeks. When it was fitted, I asked them to keep the car overnight an try it in the morning, (just to be sure they had changed the right part), they agreed. I collected I the car later that day and it has been OK since then.

Top marks to Mercedes-Benz, Preston.
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