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I have a 05 Envoy XL 5.3L 4wd. 176K miles. I've exhausted my knowledge and parts changing so I've come here for help.
Backstory: Been running great forever (isn't that everyone's story) Left me stranded, would start and die immediately over and over, was able to beat on gas tank and got it running. On drive home noticed it would stall and "cut out" like no gas was getting to it or clogged fuel filter. (fuel filter isn't beside tank like on 03-04 5.3 apparently as that was a thought I had) So Took to shop to get fuel pump replaced as that was my thought, got it back still did it few days later, replaced ignition switch, haven't had that issue but still has a "cut-out" like no fuel getting to it sometimes under load and no set occurrence, its like its random sometimes punch it and its fine, sometimes it cuts out. , after driving and turning off I get a P0001 and P0449. This is almost every time I start and drive for a few and then stop it. Codes do not appear if you delete and then re-start, you have to drive. I've replaced the Vent Solenoid Canister by gas tank ,but P0449 still appears.
My thoughts were bad gas, I put some Heet to remove water perhaps, it was on half tank, and have ran through 1/4 tank so far with same issues occurring.
P0001 to me would indicate fuel pressure regulator issue but there isn't one under hood beside intake on mine its on the fuel sender assembly that was replaced.
Modifications to Envoy:
Engine fully rebuilt to .20 over 9,000 miles ago. Texas Speed Cam with beehive springs, 2800 stall, no catalytic converters or rear o2 sensors, DOD/AFM parts removed and tuned accordingly. Been like this running great for 9000 miles with no CEL.
Bad fuel pump sender assembly? Passlock issue?
Thoughts help would be appreciated I love my envoy but this is making me crazy.
 

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2002 chevy trailblazer_lt
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P0001 to me would indicate fuel pressure regulator
To the best of my knowledge there is no such circuit in these vehicles. The fuel pump is controlled by a simple relay, no sort of modulation available and there is no fuel pressure circuitry in the ECM! I think your scanner is making stuff up when it comes to that P0001!
 

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Have you tested the EVAP vent solenoid and wiring? If that was shorted to power you could build up a very high vacuum in the fuel tank. That by iteslf can cause near stall. I have witnessed exactly this while doing a "purge and seal" test of the EVAP system. When the vacuum started to get high the truck wanted to stall.
 

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Discussion Starter #4
Have you tested the EVAP vent solenoid and wiring? If that was shorted to power you could build up a very high vacuum in the fuel tank. That by iteslf can cause near stall. I have witnessed exactly this while doing a "purge and seal" test of the EVAP system. When the vacuum started to get high the truck wanted to stall.
Ok, So, I borrowed a "Bluepoint EECR1a" handheld small scantool and it only shows P0449 stored, and P0449 pending. so... looks like that is the only code and you were right.

I have not tested the wiring, I have replaced the vent solenoid as that was my first thought and why I posted as the P0449 still came up.
I had taken it to have the fuel pump replaced as I described in my very long post, is it possible the wire got damaged or pinched and that is my issue?
Could you help me in the test procedure for the wiring, the wiring isn't that hard to get to the plug, I'm not sure difficulty on if I'd need to drop the tank to access all the wires.
All help is appreciated. I await your input.
 

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I think you said you replaced the vent solenoid valve? Or was it the canister? At any rate, at the vent solenoid are 2 wires, one orange and one white. The orange wire should have 12 volts DC positive power (relative to chassis ground) at all times. On the white wire, with the key off, I would expect there to be in the neighborhood of 12 thousand ohms resistance to ground. This white wire leads back to the ECM, passing through the underhood fuseblock on the way. It CANNOT be grounded. The ECM controls the vent valve by grounding the white wire when it is required. As far as I know, the only time that the vent valve is meant to be closed is during system leak testing.

If you find no positive voltage on the orange wire then first check for a bad fuse. If you find either an open circuit or a grounded circuit (should have ~12k resistance to ground) on the white wire then that wire would need to be traced out to locate the defect.
 

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Discussion Starter #6
I replaced Part # PV426 at AZ - Duralast Canister Vent Valve Solenoid. Its located at the rear of the gas tank.
When I search AZ for "EVAP vent solenoid " it pulls up that and Part # PV443, which is on top of engine, driver side. PV443 is the Duralast Canister Purge Valve, which I've replaced that about a 9,000 miles ago b/c I broke it when trying to remove it.

I should be able to test the wire this weekend and will report back.
 

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That's the same as my 4.2. I had thought I saw a notation in a wiring diagram that stated the long wheelbase models had it on top of the tank.
I've found a lot of things are different on 5.3 after 2005 once they introduced the active fuel management.
2003-2004 with 5.3 has a fuel pressure regulator on the driver side intake. 2005, not anymore.
2003-2004 with 5.3 have a fuel filter on front side of tank. 2005 does not.
 

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Discussion Starter #9
I did some testing, found no power on "pink" wire, no fuse was blown, tested all fuses under seat and hood, all good. Found no resistance on the white wire, also it isn't grounded anywhere so I guess broken wire, but haven't searched further for it. Even though I had no codes for it, I had replaced my MAF from my random google searching and I haven't had a stall yet. The search continues.
 

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I may be having the same issue. I drop the tank and replaced the Fuel Pressure Sensor and FORGOT to test voltage. My mechanic did a scan and said It was RIGHT what I was thinking the error was all this time was the pressure sensor and that is was not working . It could be from no voltage or bad sensor. Hopefully the light stays off for a while if it comes back on I need to find out where the power source to the pressure sensor comes from.

I am so MAD I forget to check voltage after all that work. I need a diagram to see were the power source for the sensor comes from. I saw the wires head up from the tank and towards the front of the car
 

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need a diagram to see were the power source for the sensor comes from. I s
That may depend on the particular year and engine. On the early 4.2 LL8 engines all 3 fuel tank pressure sensor wires go to PCM Connector 1. Depending on your skill set it could be tested there with a good multimeter.
 

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I’m all set the light has not come on normally after about 150 miles from the Lisa it comes on. It’s been over 260 miles. So it was no thank pressure sensor I want to take most of you are your house recently there was another person on this forum ravalli suffer That was making fun of my grammar my spacing in my vocabulary. It’s pretty sad this morning as idiots. But I’m definitely not coming back for harassment I don’t want to put something on the punctuation I’ll be made fun of
 
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