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Pete, Technician
Category: Lincoln
Satisfied Customers: 27091
Experience:  Over 17 years diagnosing and repairing automobiles various makes and models with some training and certifications.
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My Lincoln 2007 MKZ sometimes will not start when key is

Customer Question

My Lincoln 2007 MKZ sometimes will not start when key is turned and then check engine light comes on. But will start on the next try. This does not happen all the time. Also only a few times did the car when put into gear jerked but this only happened 2 times months apart. Car runs good. I have no one that knows what is wrong. Took it to the Ford and they say it is nothing they can find. Have a code reader and this came up. U0100
Submitted: 7 days ago.
Category: Lincoln
Expert:  Pete replied 7 days ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Are you seeing the check engine light with the key on when it will not start along with the other dash lights that are lighting up?Or is this a separate time you see this check engine light on?

When it will not start is the starter engaging to crank over the engine or if the starter not engaging?Are you hearing any click noises in the engine area when it will not start?

Let me know so we can continue,thanks Pete.

Customer: replied 7 days ago.
All dash lights come on when key is in the on position and car starts and goes out when running. But sometimes when I put the key in the car and turn it it does not start the car so I have to turn it off and try and restart it and then the check engine light is on and stays on. Oh and the starter not clicking or engaging when it does this.
Expert:  Pete replied 7 days ago.

I apologize for the delay.

O.k. this can be due to a fault with the electronic ignition switch itself.I have seen this switch fail/act up intermittently and cause issues like this here.If you have not had this switch tested this needs done to see if it needs replaced.This can also cause a loss communication code like you see as well when this switch is at fault.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 7 days ago.
How do I test the switch? I am done with the dealers every time I have gone in to them they ether do not know what is wrong or I have an other problem when I leave. Never had this kind of trouble with any other ford or Lincoln I have owned.
Expert:  Pete replied 7 days ago.

Below is a layout of the connector at the ignition switch.YOu want to see battery voltage around 12 volts dc on the brown/red wire.If this voltage is not present let me know as this would indicate that the switch is not the cause here.

If this has 12 volts then test the other wires for voltage as indicated on the chart.If any of these voltages are missing testing with the connector plugged into the switch back probing the wires,then the switch needs replaced.

Let me know if you need anything else and feel free to rate my help here as this is how I receive credit for my time.Your 5 star rating is appreciated

Thanks Pete

Customer: replied 7 days ago.
If you come up with any thing else I can try let me know. Still have the trouble.
Expert:  Pete replied 6 days ago.

Did you test this switch to see if the switch is faulty as posted above?