Diagnosing P0440 Code
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Diagnosing P0440 Code
My 01 Blazer LS 2-door was the victim of a dog vs sqiirrel contest. The squirrel survived, but my car didn't. The main fore and aft electrical harness was chewed in two, the rear brake hose punctured, the ABS cable to the left wheel pulled out plus extensive body damage. The insurance bill was over $3000, and three weelk in the shop.
When I got the car back, it had a full tank of gas, and there was no indication of any problem. When the gas level dropped, that's when the " Check Engine" light came on. I took the car to my local NAPA store, where they found the light to be set by the infamous P0440 code. They reset the code, and sold me a new gas cap. The code stayed away (so I thought. I had just flled up before going to NAPA). You can guess what happened next. When the fuel level dropped, the light came back on.
I called the repair shop (the local GM dealership in town), and they had me bring the car back in. After having the car for the entire day, they called to inform me that the aftermarket gas cap was failing, and that a hose at the air filter was loose, and further, they said they did nothing during the repair which would cause the P0440 code. They didn't diagnose the problem to see if the problem was the result of something they should have done, but didn't. When I picked up the car, the light was out (full tank of gas), but they still suggested that I buy their OEM gas cap. I did so, and the light stayed off. That is until the gas level dropped to the point where the test was made, and the light came on again. I've since learned that the test is made after the fuel level in the tank drops to around 85% full.
I need to do some tests on my own before going back to the shop.
I've printed the instructions on tracing the probable cause of the P0440 code, but I have no clue as to where to locate the various components spelled out in the instructions, e.g. the EVAP vent solenoid, the fuel tank pressure sensor, etc.
Any direction would be appreciated.
When I got the car back, it had a full tank of gas, and there was no indication of any problem. When the gas level dropped, that's when the " Check Engine" light came on. I took the car to my local NAPA store, where they found the light to be set by the infamous P0440 code. They reset the code, and sold me a new gas cap. The code stayed away (so I thought. I had just flled up before going to NAPA). You can guess what happened next. When the fuel level dropped, the light came back on.
I called the repair shop (the local GM dealership in town), and they had me bring the car back in. After having the car for the entire day, they called to inform me that the aftermarket gas cap was failing, and that a hose at the air filter was loose, and further, they said they did nothing during the repair which would cause the P0440 code. They didn't diagnose the problem to see if the problem was the result of something they should have done, but didn't. When I picked up the car, the light was out (full tank of gas), but they still suggested that I buy their OEM gas cap. I did so, and the light stayed off. That is until the gas level dropped to the point where the test was made, and the light came on again. I've since learned that the test is made after the fuel level in the tank drops to around 85% full.
I need to do some tests on my own before going back to the shop.
I've printed the instructions on tracing the probable cause of the P0440 code, but I have no clue as to where to locate the various components spelled out in the instructions, e.g. the EVAP vent solenoid, the fuel tank pressure sensor, etc.
Any direction would be appreciated.
Last edited by patricmc; Nov 20, 2011 at 11:03 PM.
New Member
Joined: May 2010
Posts: 90
From: in the desert
I have a 99 4 door and had the same P0440
new gas cap and vac. hoses
no change
new fuel filter and havent seen P0440 anymore
I know people will think im crazy but it's true
take it and have it smoke tested
they inject smoke into the vac. lines checking for leaks
good luck
new gas cap and vac. hoses
no change
new fuel filter and havent seen P0440 anymore
I know people will think im crazy but it's true
take it and have it smoke tested
they inject smoke into the vac. lines checking for leaks
good luck
Beginning Member
Joined: Nov 2010
Posts: 31
From: Sandwich, MA
patricmc
The fuel pressure sensor on your 2dr is part of the fuel pump but is accessable from the drivers rear wheel, there is a removeable panel allowing access to the fuel pump and sensor wiring. The evap sensor is on the frame cross member above your rear dif and is an easy and not too expensive part between 50-75 bucks. Although i've had these componets replaced there is also a common wiring issue by the transmission cross member where the wiring loom fills with road grime causing wire failure both the fuel pump harness and the evap system harness were effected by this. A cheap multimeter tester and circuit tester are available at Harbor Frieght. If there isnt a local one they have a website. I love that place and I love my 01 2dr LS
The fuel pressure sensor on your 2dr is part of the fuel pump but is accessable from the drivers rear wheel, there is a removeable panel allowing access to the fuel pump and sensor wiring. The evap sensor is on the frame cross member above your rear dif and is an easy and not too expensive part between 50-75 bucks. Although i've had these componets replaced there is also a common wiring issue by the transmission cross member where the wiring loom fills with road grime causing wire failure both the fuel pump harness and the evap system harness were effected by this. A cheap multimeter tester and circuit tester are available at Harbor Frieght. If there isnt a local one they have a website. I love that place and I love my 01 2dr LS
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