Question about 2005 Mercury Mountaineer

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Engine Failsafe Mode came on after cleaning battery cables. Vehicle will start, but won't run. No throttle

I took the battery cables off to clean them. Now the dash is displaying Engine failsafe mode. It does not react to the throttle at all. There is also a wrench icon lit. I can't drive it .. how do I fix it?

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  • Lori Feb 26, 2012

    My brother added a quart of oil .. waited a few minutes and started it .. IT WORKED! Never heard of such a thing .. but he said it happened to him in his F150. Problem solved!



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  • Mercury Master
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Fail safe is TPS sensor. When you go in fail safe the vehicle give a set amount of RPM and no throttle response the rule of thumb in fail safe is APP1 and APP2 does not agree the goal is to protect the catalytic convertor. So if the transmission was at fault you dont over rev to end up burning the Cat. Or over rev to break the engine It all boils down to a throttle body assembly as the solution

Posted on Feb 26, 2012

Testimonial: "I took the vehicle to Ford, they replaced the throttle body. Runs great now! :) "


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Posted on Jan 02, 2017


Rodney Clark

  • 2299 Answers

SOURCE: Removed battery posts on vehicle to clean and to

The fail safe mode is caused by low battery or disconnecting the battery. Now the check engine light is on because it got a code from the fail safe mode. You can try to reset it by removing the battery cable for 10 minutes again. This may cause the fail safe mode again and start the whole process over again. The fail safe mode should not come up again though. Make sure that the key is off when you remove and replace the battery cable.

Posted on Oct 26, 2010


  • 1 Answer

SOURCE: I gave a 2005 Mercury

I have the same car and HAD the same problems. Just got it back from the Tranny shop, seems to have fixed the issues. Take it to a very good transmission shop and tell them it is a known issue, some kind of bearings in the tranny, hence the knocking...

Posted on Jan 31, 2011


  • 5692 Answers

SOURCE: 05 Mercury Montego Throttle control/sensor

Try a salvage yard for the part. As soon as your new car left the lot it became a used car. Used cars run on used parts.
If the old part is a recall they will upgrade you regardless which part is on your car.
Check the internet and enter your part# in the search box of the Browser. You may get lucky for a new part.

Posted on Aug 18, 2009

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Engine Failsafe Mode is activated

It may be if you ignore the light. Check the oil level and coolant levels first if ok have the fault codes read to determine the sensor that put the light on. Repair it and go from there.. Normally the ECM goes into safe mode to protect the engine and gear box from serious damage but it depends on the driver to react promptly to stop further damage occurring.

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Failsafe engine mode

You might try to have your battery tested. The Anti-theft system reacts to low battery voltage and automatically reduces the Voltage to the starter so it will not turn over or turn over fast enough to start; thereby defeating thieves.

Failsafe usually is an extreme heat sensor mode which deactivates some of the cylinders so the engine exhausts excess heat through the exhaust valve. This is why top speed is limited and power is reduced. The deactivated cylinders act like air compressors, they have no fuel charge, and thereby draw air into the cylinder and expel heated air.

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My ford explorer 2005 has a engine failsafe mode

Check engine light on , failsafe mode . The first thing to do would be to hook up a scan tool an check for DTC'S - diagnostic trouble code's . Was the vehicle overheating ? Failsafe mode will shut the vehicle off to save the engine if it is over heating . Do you know if the vehicle has electronic throttle control ? Was their a yellow wrench symbol lit on the instrument cluster as well ?

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Ford 2004 e250 after cleaning/removed battery terminal, won't start or engine won't running, fuel 1/2 full, this happen after disconnect +/- battery terminal remove.

If you indeed installed the positive battery cable last and the neg first you blew the computer possible, you will need a complete diagnosis.

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What does failsafe engine mode mean?

Hi there, Failsafe engine mode means that there's something wrong with your car. This feature limits you to 30% throttle to allow you to get safely off the highway or to a shop. It is a safety feature so you're not stranded somewhere.
This is most commonly seen when the brake switch goes - it is possible to fix it with a lot of WD40 to get the contacts going again. The brake switch is under the dash connected to the brake arm.
If you take it into a shop, they may want to replace it. It will be at least $50 for the part.

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Coding a 2106 and a 2135 on 2006 Ford Expedition. Replaced the Throttle monitor sensor and cleaned the throttle body. Drove car and it ran good but next time it did the same thing. Engine failsafe and...

You need to determine if the ETC Failsafe is from a
bad throttle body motor (TACM) or coil misfires that are
putting it into failsafe.

The TPS Sensor you replaced,wasn't likely the issue.

Put in new spark plugs
The champion 1 piece ones 7989-- from Napa CHA 7989

You will need the Lisle 65600 Broken Spark Plug Remover Tool
as you will get a couple OEM 2 piece glued together ones break.

Remove PCM from fire wall to get to #4 Plug on pass side

Change the front O2 Sensors at 100,000 miles & clean the MAF
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Solution for the message "engine fail safe mode" in explorer 2005

I have hearing a lot of this lately with Fords. Most of the time this dash board light comes on due to problems with the Throttle Body (TB)not just your coolant,etc.. If it is sticking,dirty,causing misfires,etc. then this can cause an engine fail safe mode.You might first try putting in some injector cleaner and a higher grade of gas.Many people I know who have had this problem have had to have their TB cleaned and/or replaced. This is something Ford dealerships now about,but hasn't been made a recall or anything.There are service bulletins though.Mainly keeping cleaner in your gas and performing ritual tune-ups/oil changes may be the only thing you can do.Hope this helps

Apr 17, 2010 | 2005 Ford Explorer

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