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Lincoln Forum: 2012 Undiagnosable fault MKZ
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  1. #1
    Join Date
    Dec 2017

    2012 Undiagnosable fault MKZ

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    4 trips to dealer. Zip. They can't diagnose. Car is operating fine then throws a warning to "Service Advance Trac". Then the car stops running and won't restart and throws a bunch of other error messages--check charging system, fuel level low (it's not), high engine temperature (it's not) blind spot system fault, cross traffic system fault, high motor temperature, starter system fault. By the time the dealer looks at it there are no codes no warnings nothing . They have had the car for a month and have driven it lots but it never happens when they are driving it.

    Sometimes it's months between incidents this last time it was less than a week. always the answer is the same- no matter how long they keep it they can never get it to give them a code so they can diagnose what the problem is. This car is covered by both the Certified pre-owned warranty and the Ford Premium warranty. The only thing they tell me now is that we can't fix what we can't diagnose.

    Anybody know of any similar problem that might be able to give me some info about what to have the dealer do? Feels now like I can't sell the car and ca't drive it safely. Any help would be appreciated. Tanks JOHN

  2. #2
    Slick Fan's Avatar
    Slick Fan is offline Senior Member My Lincoln(s): 2003 TC Signature, 1977 TC, 2003 Aviator
    Join Date
    Jan 2014
    Wow, that's a crazy problem! It sounds to me like a power control module is going bad, but with no trouble codes, it would be pretty hard to say with certainty if one or more is the culprit.

    Hopefully someone else will chime in with a similar issue to yours, I wish I could be more help.

  3. #3
    Join Date
    Mar 2014
    Ann Arbor, MI
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    Sorry for the late reply, I saw this thread a while back, thought I replied back then but I guess not Hopefully you've gotten it fixed already, but if not here are a few things that should be looked at either for your benefit or for someone else who runs across the same issue.

    This screams of a fault in a power circuit. My first thought was the Powertrain Control Module (PCM) relay. It would certainly explain the car shutting down and not restarting, but this shouldn't generate errors for the blind spot/CTA system or fuel level. Even so, I would replace the relay first. It's cheap and easy to get to (in the fuse box under the hood). If the relay is failing or getting intermittent contact in some conditions, you could get some unrelated error messages if the car's network gets overwhelmed by bad data from the PCM.

    The common thread with all of these errors is that these systems receive power through the Smart Junction Box (SJB) when the key is in start or run. The SJB is the fuse box near the driver's footwell, but it also contains what is essentially a small computer that controls many vehicle systems. These can fail or have intermittent faults with some truly bizarre symptoms. If it is not providing consistent power, it would explain all of these issues.

    The third options is the instrument cluster itself, as it is also integral in managing all of these systems. This is somewhat less likely. The trick with all of this is that the fault could be with a module or with the wiring in between. As part of the diagnostics, a good mechanic would inspect the wiring, and especially the ground points for these modules where the common grounds come together. If the car has been in an accident or had major work (think engine or dashboard removal) these connections would be the first to start with.


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