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Ben ATX

P0440 code , what could be causing this code

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I have had this p0440 code on my 2000 eldorado esc for a while , amd i know i need to fix it . I have no pressure when i remove the gas cap . What are the possible problems , amd possible fixes for this code ?I can smell gas  faintly towards the rear of the car and have been getting low mileage as well. Any ideas .?how can i figure out what needs to be fixed to make this code go away?

Edited by Ben ATX

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On many of these cars, the filler tube (the pipe the gas cap screws on to) rusts out somewhere on it's run to the gas tank.  You should crawl under there, follow the filler tube, and look for rusted out sections.  Also, check the rubber lines that they are all tight. I don't know if it can be as simple as a faulty gas cap.  I never heard a hiss or air when I took my gas cap off on my '96.

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I have a feeling its not the gas cap . I am trying to figure out how much the reairs for the filler tube would be so it will stop this code . I cant pass emissions with the p0440 here in austin.

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Sometimes the cap can be loose or missing a seal and cause this.  I once forgot my cap on top of the gas pump at the station and got the code.

As winterset points out, the pipe between the filler and the tank can rust, it happened on my 96 and I replaced one on my friends 95.   You can smell gas fumes when its rusted through.  it should not affect your gas mileage however. 

Post all of your P codes

The cost of repair depends on the cost of the part, I see the cost all over the board.  Rockauto does not list the part, a search on ebay turned up this, get the part number from the dealer and match it up.  Dorman does not list it on their web page.  You may be forced to go to the dealer or scrapyard if you can find a good one.   It is not too hard to install.

http://www.ebay.com/sch/i.html?_odkw=cadillac+fuel+filler+neck&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xcadillac+eldorado+fuel+filler+neck.TRS0&_nkw=cadillac+eldorado+fuel+filler+neck&_sacat=0

 


Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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On Friday, December 09, 2016 at 0:15 AM, BodybyFisher said:

Sometimes the cap can be loose or missing a seal and cause this.  I once forgot my cap on top of the gas pump at the station and got the code.

As winterset points out, the pipe between the filler and the tank can rust, it happened on my 96 and I replaced one on my friends 95.   You can smell gas fumes when its rusted through.  it should not affect your gas mileage however. 

Post all of your P codes

The cost of repair depends on the cost of the part, I see the cost all over the board.  Rockauto does not list the part, a search on ebay turned up this, get the part number from the dealer and match it up.  Dorman does not list it on their web page.  You may be forced to go to the dealer or scrapyard if you can find a good one.   It is not too hard to install.

http://www.ebay.com/sch/i.html?_odkw=cadillac+fuel+filler+neck&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xcadillac+eldorado+fuel+filler+neck.TRS0&_nkw=cadillac+eldorado+fuel+filler+neck&_sacat=0

 

But if the vapors are not being caight by the charcoal canister and the vapors are  reused as has eventually i thought . Plus there is no vaccum seal i was think maybe a loose seal , but you are probably right . A rusted part, or seal, but i think the corrossion might be on a lower part of the car actually causing a small gas leak ,possibly in the tank. What the car is constantly saying even without pulling the dtc codes is check gas cap . I have only two trans codes, a p0440 and a p0741, and the more i read , these two codes are so common it seems like with these cars. I do have access to a 2001 esc with 50000 miles on. Again i am getting about 14 somtimes 13 miles to the gallon. I read that a 2000 or earlier model car is actually allowed two unprepared trans codes for inspection , after 2001 only one trans code . And there are options with various programs that will provide 600 dollars towards fixing the transmission so that the emissions are lowered, the clean air act . Or it will give you 3500$ towards a mew car with no emissions problems, bit it has to fit very specific criteria. However i am kind of set on carrying out my project ,i giess i have a bond with the car,lol . So its just a matter of pinpointing the p0440 code source. Still not sure the best way to start to look for it . Do you have any suggestions on that matter of how the best way to start looking for it might be ? Thank you for your help

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P0440, is related to the EVAP system NOT being able to create a vacuum, either because the cap is LOOSE, DEFECTIVE or the filler is porous from corrosion.  You said you were smelling fuel, is that fuel smell by the left rear wheel well?.   Typically, the fuel smell comes from the filler pipe that rusts through given that you have a P0440, that is a logical assumption.  Since I can not see, you will need to look at the filter pipe from under the car and after removing any covers or inspection covers to get a look at it.

P codes are NOT transmission codes they are Powertrain codes.   The fuel tank can not rust through, its an impact resistant plastic of some sort.

As far as your gas mileage, you will need to reset everything on your dash, miles, mpg, mph, etc then look at it.  Local driving will only get you about 12 to 14 mpg and highway about 22 to 25, real life driving will be a blend of these two styles of driving, so if you have only been driving local, the 12 to 14 does not bother me.

DTC P0440 Evaporative Emission (EVAP) System

System Description

The control module tests the evaporative emission (EVAP) system for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge valve OPEN and the EVAP vent valve CLOSED . This allows engine vacuum to enter the EVAP system. At a calibrated time, or vacuum level, the control module commands the EVAP canister purge valve closed, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum level. If the system is unable to achieve the calibrated vacuum level, or the vacuum level decreases too rapidly, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent valves.

Control Module Command

EVAP Canister Purge Valve

EVAP Canister Vent Valve

ON

Open

Closed

OFF

Closed

Open

Conditions for Running the DTC
  • DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0443, P0449, P0452, P0453, P1106, P1107, P1111, P1112, P1114, P1115, P1121 or P1122 are not set.
  • The ignition voltage is between 10-18 volts.
  • The barometric pressure (BARO) is more than 75 kPa.
  • The fuel level is between 15-85 percent.
  • The engine coolant temperature (ECT) is between 4-30°C (39-86°F).
  • The intake air temperature (IAT) is between 4-30°C (39-86°F).
  • The start up ECT and IAT are within 9°C (16°F) of each other.
  • The vehicle speed sensor (VSS) is less than 121 km/h (75 mph).

Conditions For Setting the DTC

The EVAP system is not able to achieve or maintain vacuum during the diagnostic test.

Action Taken When the DTC Sets
  • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
  • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
  • The control module will turn the malfunction indicator lamp (MIL) OFF during the first consecutive trip in which the diagnostic has been run and passed.
  • A last test failed (current DTC) clears when the control module turns OFF the MIL.
  • The history DTC will clear after the control module runs and passes 40 consecutive warm up cycles with no failure.
  • The DTC can be cleared by using a scan tool.

Diagnostic Aids
  • Use the J 41413 EVAP Pressure and Purge Station in order to pressurize the EVAP system to aid in locating intermittent leaks. Move all EVAP components while testing with the J 41416 Ultrasonic Leak Detector.
  • A temporary blockage in the EVAP canister purge valve, purge pipe or EVAP canister could cause an intermittent condition. To repair a blockage in the EVAP system refer to Evaporative Emission (EVAP) System Cleaning .
  • Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step verifies proper operation of the fuel tank pressure (FTP) sensor.

  2. This step tests the EVAP canister purge valve for a restriction or blockage.

 


Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I'll go with the other inputs. Fuel cap leak or a pipe leak due to rust. I had that problem on my STS. Turned out to be the fuel cap.

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Okay, I had the same issue with my (California) 2001 STS for almost 2 years.. After replacing every serviceable  part of the evap system, (i.e  purge solenoid, vent solenoid, canister, fuel pump seal, gas cap, and connection o-rings. It still triggered the p0440. So recently I built a smoke machine (from a youtube video) broke down each section of the evap system, and smoke tested it,and what I discovered was the filler neck itself was leaking at the cap location, not the cap, but between the cap & filler neck. There's an o-ring between the steel flange, and  plastic filler neck that rots out.This is not a serviceable item ( however I did replace the o-ring on mine but that's tricky) you should replace the filler neck unit (with a new one) which is entirely accessible, and not difficult to do. Also check the clamps which attach the plastic filler neck to the tank. 

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