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2002 gmc envoy_sle
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Discussion Starter · #1 ·
02 Envoy with 80,000 miles. My wife drove to the doctor fine this morning. I get in it one hour later and try to crank through the open window while holding my daughter and it tried to run for about a split second and died. Now it turns over but will not even attempt to run. It turns over really good. The battery is fine. Checked the gas cap. Its tight. Unhooked the battery for about 15 minutes,(is that long enough) that didnt work. All the lights still work and I can hear the fuel pump priming. I checked some of the fuses I thought could be it and didnt find any blown although I didnt know what some of them stood for so dont rule this out. Had this car for over 3 years and never had a problem until now. I searched 7 pages on here and 90% of threads were for the truck not even turning over. Any help is appreciated. I am fairly lost with newer cars but Ive been spinning wrenches on 1st and 2nd Gen small blocks my whole life. This is our only family car too. Thanks.
 

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2002 gmc envoy_sle
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Discussion Starter · #3 · (Edited)
No sir^, just service engine soon and reduced engine power. Are those supposed to stay on? It didnt have either light on before when it was running.
I also noticed that a few times it would continue to crank even when I let go of the key.
 

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2004 gmc
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2002 gmc envoy_sle
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Discussion Starter · #5 ·
Thanks roadie. I have never noticed it continue to crank before. How come it only does it about half of the time?
I thought about the ignition switch but it was my understanding that if the ignition switch was bad, it wouldnt even let me turn the engine over (spin the starter). Can you clear that up for me?
The shifter moves freely through all gears but will not start in nuetral or park.
I hope it is just the ignition switch because its easy to replace. Is there any way to test it? Thanks alot.
 

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2004 gmc
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The ignition switch has a lot of functions, and one of them is to power the PCM and engine controls WHILE the starter is cranking. That's what might have gone bad for you. You might also have a bad fuse in the PCM chain, and I'd recommend you check them all out under the hood. The rear fuse block doesn't have anything critical in that chain.

Testing the ignition switch requires a meter and a schematic and a bit of experience. I can post parts of the schematic, but I don't know if you have a meter and know how to use it.

Important fuses are 10, 22, 23, 28, 29, and 47 under the hood.
 

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2002 gmc envoy_sle
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Discussion Starter · #7 ·
I just got finished checking every fuse and they were all visibly good. I think I will just replace the ignition switch. I have a buddy that gets me a good discount so I can pick one up for around $12. Didnt look like it will take that long to replace. I will let you guys know how it works out. Any further suggestions?
 

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2003 chevy trailblazer_ls
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Yes, you said that you can hear the fuel pump running. Try to start it 2-3 times and then quickly pull a plug and see if it is wet with gas. That will tell you if the coils are fireing or not. If they are dry then the injectors are not working. Last shot is starter fluid, but I do not like shooting ether in the intake. Bad things can happen.
 

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Discussion Starter · #9 ·
Okay heres what I just did. I went out and removed the airbox on top of the engine to get to the plugs and then I went and proceeded to try and start it a few times first. Right before I tried to start it, I moved the steering wheel all the way up to take a look at the panels below to see what I was up against for the ignition switch. I left the steering wheel all the way up. I then turned the key and it ran for about 1-2 seconds and then died. It wouldnt run again after that. Same symptoms as before. So I tried 2-3 times and then pulled 2 plugs. They were both dry. I didnt see any wetness. So what now? Im still leaning towards the ignition switch because of the fact that it just started and ran a little.
 

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2002 gmc envoy_sle
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Discussion Starter · #10 ·
Well I finally got a new ignition switch and installed it. Still wont run so its not the ignition switch. Where is that Shrader valve on these cars so I can see if it has some fuel getting up there? I saw a green cap on the drivers side but when I depressed it there were no signs of any fuel or anything. I did it while the car was on and after the fuel pump primed. Shouldnt there be gas there? (If thats the right shrader valave)
 

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2003 chevy trailblazer_ls
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on your 02-- there is a schraeder valve right next to the fuel filter.
the filter is located by the tank- underneath the vehicle.
next to the vehicle frame. It has a screw on cap. in the pic Ive removed the cap and pressed to release gas/pressure.
On my 03...
 

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Discussion Starter · #12 ·
Thanks. I will try that as soon as it stops raining here. So what was the one with the green cap I depressed in the engine compartment? I know it wasnt A/C so it had to be a fuel line.
 

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Discussion Starter · #14 ·
^ I havent changed it. We've had the truck about 3 years. I couldnt tell you if the previous owner changed it or not. I was just going to get around to doing a tuneup soon. I've had alot of cars but I've never seen a fuel filter that was completely clogged. Can this happen? I imagine it could but isnt very likely.
 

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Discussion Starter · #15 ·
Alright made some progress today but still cant get it to run. I checked the Schrader valve right next to the fuel filter and it has tons of pressure. So that rules out the fuel pump and the fuel filter. I checked a spark plug to see if it was arcing and it has spark. So the engine is getting spark. I then got my buddy to borrow the scanner form autozone and 2 codes were retrieved. The Codes are P1515 and P1516 - Manf control veh spd Idle speed control Auxilary inputs. Do these codes have anything to do with it not running?
Please lend a hand guys if you have any advice to give. I could really use the help. We were supposed to go out of town next weekend in this car. What should I do next?
 

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2007 chevy trailblazer_ls
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NO, that green one is for the emissions crap. There is one located next to the fuel filter.
 

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Forget my last reply......forgot to go to page 2!!!! Fuel filter can get plugged solid, had it happen to my saturn last year. What usually will happen is the pump will over heat the relay and the car would shut off periodically then ryn again for a short period of time etc.
 

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I got a little different description of the codes you had, here is what my manual said:

P1515 : TPS, difference between actual and detected throttle position

P1516 : TPS sensor out of range.

I believe this could cause your no start if it doesn't know how much fuel to deliver or the injector pulse for the throttle position. Try the screw driver on the top of an injector to see if it's pulsing or not???:m2:
 

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Moving the gas pedal, causes the butterfly in the throttle body to move, but these trucks use a "drive-by-wire (electric) throttle.

Therefore, we have sensors to tell the PCM where the throttle pedal is at any time.

We have 2 sensors at the throttle and one at the throttle body. This problem is usually the throttle position sensor.

But, it could be a broken/shorted wire between the 3 devices.

A quick test that I would try: turn on key and have someone move the gas pedal while you watch the throttle body butterfly move. Sounds like your butterfly is not moving.
 

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Alright, Right out of the manual:

" The throttle position sensor (TPS) is a variable potentiometer connected to the end of the throttle shaft inside the throttle body. By monitoring the output voltage from the TPS the PCM can determine fuel delivery based on the throttle valve angle."

Hope this helps.:thumbsup:
 
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