Question about 2004 GMC Envoy

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2003 Hummer H2 check engine light is on steady

Reduced Engine Power  & when we increase speed the check engine light begins flashing

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  • ayman_1963_n Jan 27, 2009

    thank for you

  • peabs46 Mar 04, 2009

    03 hummer h2 reduced engine power light and reduced engine power takes place .. shut it off a couple of times and power regains but engine light stays on

  • 427sccobra Apr 13, 2009

    I have the same problem and Autozone read the codes and said it could be one of four issues, plugs and wires (changed and did not fix) ignition coil (next step) , Cam position timing sensor, and fuel pressure regualtor. May question is how many coils does the engine have? It looks like there are 8??? Can anyone answer this question?

  • Anonymous Mar 19, 2014

    Reduced engine power light comes on intermittently

  • Anonymous Apr 01, 2014

    2003 reduce engine power



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This is Obama's new energy policy to to save gas !

Seriously, go to Autozone and they'll read the code for free.

Posted on Jan 27, 2009

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You need to have it scanned for codes

Posted on Jan 27, 2009


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Apr 16, 2016 | 2008 Hummer H2

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My hummer H2 2003 did the same and I checked the coolant it was low.Refill the coolant and start the vehicle,if problem of reduced power persists check the thermostat if its not faulty.Hoping this will solve your reduced poweproblem

Sep 26, 2014 | 2003 Hummer H2

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I got the engine light on steady in my hummer h2 when i opened the hood i saw the antifreeze tank was empty.I filled up it but the engine light was on still.I got the leaking windshield and maybe the wires...

You are wasting your time trying to guess why your engine light is on. Most auto parts stores will scan your car for free and tell you why the light came on. Get this done, then ask us how to fix it.

Aug 19, 2011 | 2003 Hummer H2

1 Answer

Reduced engine power, warning displayed in panel. No acceleration Hummer H2 ,2003- 4.3 vortex. Tried disconnecting battery to reset, failed.

Needs to be put on computer to read codes to see whats going on.Could be one of many things going on there.

Mar 08, 2011 | 2003 Hummer H2

1 Answer

H2 reduced engine power

Check the throttle body first see if it's opening all the way when you press the gas

Jan 29, 2011 | 2003 Hummer H2

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Check engine light is on steady , but guages look normal and engine seems normal and running fine with no problem.

If it is OBD2 Then have it scanned, most likely it is something simple as a blown fuse or faulty wiring.

Jan 11, 2010 | 2003 Hummer H2

1 Answer

My check engine light is blicking and i cant go over 20 mph but the engine will get to 3000 rpm

sounds like a skip if the light flashes. your vehicle goes into a limp mode if it detects a problem to prevent further damage. this is why you cant go over a certain speed of rpm

Oct 03, 2009 | 2003 Hummer H2

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2003 Hummer H2 overheats while idling in Park


May 13, 2009 | 2003 Hummer H2

1 Answer

Car loses power

When the check engine light is flashing that indicates an engine misfire, which is catalyst damaging. Because you said that it generally only happens up a long hill or at higher speed, and it doesnt happen all of the time, most likely you are in need of a full tune up.

Dec 11, 2008 | 2003 Hummer H2

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