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2003 gmc envoy loss of power
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jrflauta
New User
Dec 7, 2011, 10:56 AM
Post #1 of 7
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2003 gmc envoy loss of power
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2003 gmc envoy loss of power light car will not start, it will crank but wont turn over. pls help
(This post was edited by carjunky on Aug 25, 2016, 6:01 PM)
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 7, 2011, 11:56 AM
Post #2 of 7
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Re: 2003 gmc envoy loss of power light car will not start, it will crank but wont turn over. pls help
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Yep, if it won't start, that's a pretty big loss of power.
All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.
Every engine requires spark, fuel and compression to run. That's what we have to look for.
These are the basics that need to be tested and will give us the info required to isolate a cause.
1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.
2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.
3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.
4) If all of these things check good, then you would need to do a complete compression test.
Once you have determined which of these functions has dropped out,
you will know which system is having the problem.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
/ Moderator
Dec 7, 2011, 4:20 PM
Post #3 of 7
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Re: 2003 gmc envoy loss of power light car will not start, it will crank but wont turn over. pls help
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Now this is where that systematic chart may lead you down the road to a dead end.
The loss of power light means the electronic throttle control system (ETC) has a problem and the PCM (powertrain control module) has detected this. There are different actions the PCM will take depending on the type of problem that is popping up. One action is that it will disable the ETC system/fuel injectors and you won't be able to start the vehicle.
First thing that you need to do is to scan the PCM and see what trouble code it is storing for the ETC system.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 7, 2011, 4:24 PM)
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Hammer Time
Ultimate Carjunky
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Dec 7, 2011, 4:35 PM
Post #4 of 7
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Re: 2003 gmc envoy loss of power light car will not start, it will crank but wont turn over. pls help
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An Electronic throttle problem will give you reduced throttle or no throttle at all but will not cause a no start so the chart applies. It may just be a little difficult to check injector pulse but not impossible.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Hammer Time
Ultimate Carjunky
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Dec 7, 2011, 5:10 PM
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Re: 2003 gmc envoy loss of power light car will not start, it will crank but wont turn over. pls help
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I'm really getting tired of your crap mouthpiece...................
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
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Dec 7, 2011, 5:20 PM
Post #7 of 7
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Re: 2003 gmc envoy loss of power light car will not start, it will crank but wont turn over. pls help
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Well, I am sorry you feel that way. I am just trying to point out that sometimes the chart can take you on a wild goose chase. Most of the time your chart is going to work, but in this case maybe not. I apologize if I insulted you, but you did learn something today that you didn't know. I am very sure that there are things that you know that I don't and you'll point that out. One fellow tech helping the other, right?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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