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Discussion Starter #1
I have a 2004 GMC Envoy I purchased not too long ago. Recently, as in 3 or 4 days ago, the REP light has been coming on very often. Has only come on once before and had not been back on since. Until now. Now as soon as I take off it only takes a couple minutes to come on. I made it to the auto parts store when it came on and got the following codes. P2135 Throttle/Pedal Position Sensor/ switch a/b voltage correlation
P2138 Throttle/Pedal Position Sensor/ switch d/e voltage correlation.
P1680 CONTROL module accelerator pedal position (app) system performance.
P0641 Sensor reference voltage a circuit/open
P0014 Exhaust camshaft position timing - over-advanced bank 1
P0410 secondary air injection system.
And again P2135/2138

I have read a couple posts discussing the throttle position sensor or the pedal assembly, along with a couple other things. I was wondering if this is the most common problem that I should tackle first or if there is anything else that might be viable to try first.
 

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Discussion Starter #2
Going to the autoparts store to pick up the accelerator pedal position sensor now, will repost with results. Fingers crossed
 

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Some folks who experienced this have found either a shorted wire in the harness that goes to the fan clutch or a defective fan clutch itself. The problem has to do with a 5V reference voltage that is also used by the throttle body and the accelerator pedal sensors.
 

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Also, it's not just a sensor - it is an entire accelerator pedal assembly.
 

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Discussion Starter #5
Yes I replaced the accelerator pedal assy. No difference. I did notice this morning though that it did run fine until it got up to operating temp. Around 210 deg. Then it died for the first time. Also it does produce a strong gas smell when this starts to happen. Seem like the fan clutch?
 

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Discussion Starter #6
Also, someone had posted on another thread that the next time the REP light comes on the disconnect the fan clutch connector and see if the light goes out. Does this seem like a reasonable experiment to anyone? I just don't want to try one thing that causes another. As in I replaced the ACC pedal assy took it for a test drive and lost a coil pack. Maybe unrelated idk. Anyone with a suggestion. I'm between the fan clutch and the throttle body for replacement. Only have money for 1. Best bets???
 

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Since you are smelling gas, check your fuel pressure regulator for proper operation. It might have a busted diaphragm and is leaking gas.

Regarding the disconnecting of the fan clutch question, that is a quick and dirty way of seeing if the problem is caused by bad electronic fan clutch. When it goes bad, it can ground out the 5 V reference voltage and cause havoc with the other engine control systems.

Replacing the accelerator pedal assembly has nothing to do with an ignition coil going bad. Purely coincidental. Coil was likely weak for a while and then chose that time to give up the ghost.
 

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Discussion Starter #8
Just a quick update. Went out and got a new throttle body. Figured hey, truck hasn't been running tip top and it looked tired, and maybe it's my problem. Made it about a quarter mile before REP. Seemed like at one point the other day when idling I smelled something. That distinct smell if u had stripped the jacket off a wire to expose the copper and took a lighter to it. First and only time too. If anyone with prior knowledge of this electrical issue with the frayed wire in the harness can point me in the beat area to start looking it'd be much appreciated. All you guys been awesome trying to help me out thank you guys and gals.
 

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Discussion Starter #9
Since you are smelling gas, check your fuel pressure regulator for proper operation. It might have a busted diaphragm and is leaking gas.

Regarding the disconnecting of the fan clutch question, that is a quick and dirty way of seeing if the problem is caused by bad electronic fan clutch. When it goes bad, it can ground out the 5 V reference voltage and cause havoc with the other engine control systems.

Replacing the accelerator pedal assembly has nothing to do with an ignition coil going bad. Purely coincidental. Coil was likely weak for a while and then chose that time to give up the ghost.
Thanks for the input. Figured it was just by chance the coil went. I will try that with the fan clutch and see what happens. Also. I do now have an acc. Pedal and throttle body that I don't much need because I replaced them, for no reason apparently they are still just fine. If someone is in a bad spot and honestly needs one of these parts I'd consider donating to the cause. Parts ain't cheap and most people can't take a few hundred dollar hit without flinching.
 

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Thanks for the input. Figured it was just by chance the coil went. I will try that with the fan clutch and see what happens. Also. I do now have an acc. Pedal and throttle body that I don't much need because I replaced them, for no reason apparently they are still just fine. If someone is in a bad spot and honestly needs one of these parts I'd consider donating to the cause. Parts ain't cheap and most people can't take a few hundred dollar hit without flinching.
Hey , I'm in the same boat right now. Ive got a 03 trailblazer doing these exact same things. Im stumped as to what it possibly could be anymore also. I replaced the throttle bosy, gas pedal, all the plugs , few of the coil packs. Still does it.
 

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A couple of things. First are there any OBDII codes, and if yes, what are they? Second, have you changed the fuel filter? Third, have you checked the fuel pump pressure? Lastly, have you checked the fuel pressure regulator for proper operation? Also, if you do not already have one, purchase a Haynes manual for your TrailBlazer - it will prove invaluable to you in troubleshooting and maintaining your TrailBlazer.

Welcome to the forum and Good luck!
 

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Discussion Starter #12
Hey , I'm in the same boat right now. Ive got a 03 trailblazer doing these exact same things. Im stumped as to what it possibly could be anymore also. I replaced the throttle bosy, gas pedal, all the plugs , few of the coil packs. Still does it.
Also I was told the fan clutch uses the same 5v reference as the accelerator pedal and throttle body. I guess it's a real common problem. I was told by several people that at this point it's either a faulty fan clutch or one of the wires coming from the fan clutch to the PCM is frayed and short circuiting and like I said this is a very common problem with the fan clutch causing the REP to kick in.
 
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