Wont shift and th engine light flashes on and off and it loses power what is it

If the engine light is on there is a problem. You should not cause any damage if you delay the repair and continue to drive your Yukon. Just as long as the engine is performing normal. No loss of power, delayed shifting or any performance issue that seems new. If the engine light starts flashing while you are driving then you must stop driving it. Continued driving with a flashing engine warning light can result in engine damage. Also you are the eyes and ears inside your Yukon. You must observe how the truck is operating while it is running. If the engine stalls, shakes, loses power or has a rough idle. I would stop using it as well and have it diagnosed. Please let me know if there is anything else. Good luck.

You did not post the year make and model BUT you should not drive the vehicle because when the check engine light flashes, you can cause damage to your engine. You need to get an OBD reader from a chain autoparts store and see what codes are present.

stock engine?
i did not decode that, at all.
has power? (what 12vdc power or engine power)
turn key it wont start but does it crank.??????? fast..
and lose power, what power is lost 12vdc power or engine runs but lost power?
the power is back what power? name something, specific,
like 12vdc power, starter power, engine power.
the starter wont work, i take that its silent?
or
starter spins but engine dont?
or starter clicks
or starter, is weak
or ???? try to be clear,

no engine stated.
no transmission.

if stick shift the clutch switch must work or the starter will be dead.
does that help
ever hot wire a starter, see this.
http://www.fixkick.com/nocrank.html

if engine will not crank, say that.
then say sounds. it makes if any.

NEED TO SCANN TH CAR

Hi there.
Well because its a auto box you could have a band or pump problem which is in the gear box and is bathed in auto matic fluid oil and that could be your problem as the bands do wear down fast on a lot of cars and BMW with there power that could be you.
So take it to a auto box people and get it checked out.

the name of this transmission is hydrAmatic not hydrOmatic it is made by General Motors , i cant find a reference to g14 ,look for serial number begining TH___ or 4L or 4T as these cover the age of your vehicle

For gear shift issues and gear stuck issues,the help links are provided below. Click the link below to go through troubleshooting procedure:---- ---- Car will not move when in gear?

http://repairhelpcenter.blogspot.in/2012/02/car-will-not-move-when-in-gear.html ---- transmission sticks in first gear? http://technoanswers.blogspot.com/2012/01/mercedes-benz-transmission-sticks-in.html ----- Transmission not engaging in first gear? http://technoanswers.blogspot.com/2012/01/mercedes-benz-not-engaging-in-first.html ----- Vehicle only goes in First gear?

http://howtobyme.blogspot.com/2011/11/chrysler-pt-cruiser-only-goes-in-first.html

----

Car is stuck in park and the shift will not move?

http://howtobyme.blogspot.com/2011/08/car-is-stuck-in-park-and-shift-will-not.html

---- Engine will not go out of park mode? http://technoanswers.blogspot.in/2012/02/2002-nissan-sentra-will-not-go-out-of.html ---- Car stuck in park? http://technoanswers.blogspot.in/2012/02/nissan-sentra-stuck-in-park.html ----- Car will not come out of Park?

http://howtobyme.blogspot.com/2011/11/car-will-not-come-out-of-park.html

-----
Automatic transmission will not go into high gear?

http://howtobyme.blogspot.com/2011/11/automatic-transmission-will-not-go-into.html
--- Car wont downshift sometimes?

http://schematicsdiagram.blogspot.com/2011/12/car-wont-downshift-sometimes.html
---- Transmission will shift into drive?

http://schematicsdiagram.blogspot.com/2011/12/buick-park-avenuetransmission-will.html
----- Auto wont shift from park? http://schematicsdiagram.blogspot.com/2011/12/ford-taurus-wont-shift-from-park.html ---- Car Transmission will not go into Park mode?

http://schematicsdiagram.blogspot.com/2011/12/car-transmission-will-no-go-into-park.html
----- Shift indicator directly goes to 2nd when key is turned ON?

http://schematicsdiagram.blogspot.com/2011/12/shift-indicator-directly-goes-to-2nd.html
---- Third gear missing and engine losing power?

http://schematicsdiagram.blogspot.com/2012/01/third-gear-missing-and-engine-losing.html
------- Vehicle has whining sound in gear?

http://technoanswers.blogspot.com/2012/01/chevrolet-silverado-has-whining-sound.html
----- Hard to shift gears on Manual transmission?

http://technoanswers.blogspot.com/2012/01/hard-to-shift-gears-on-manual.html
------ Car hard shift at slow speeds?

http://technoanswers.blogspot.com/2012/01/car-hard-shift-at-slow-speeds.html
--- Automatic transmission shift lever hard to move on cold mornings?

http://technoanswers.blogspot.com/2012/01/automatic-transmission-shift-lever-hard.html
------ Gear shifts hard?

http://schematicsdiagram.blogspot.in/2012/02/2000-nissan-maxima-shifts-hard.html
------- Vehicle noticed sluggish delayed shifts while driving?

http://schematicsdiagram.blogspot.in/2012/03/vehicle-noticed-sluggish-delayed-shifts.html

-------

This will help.

Thanks.

Might be a modual needs replacement

I don't know your year, but transmissions shifting is partly controlled by the throttle position sensor. Have the computer check for codes. If the TPS comes up this is most likely your problem.

When did the spark plugs last get changed? May need new spark plug wires.