CEL code PO455

[ygu]

Dose anyone know what I can do to fix this? I did a search on the forum and only found one post and it mentions the fuel cap. Is it possible it is something that simple? Please help... thanks.

 

[Nick26]

I believe I got the same number on my 5Spd w/50K, and the shop told me it could have been a variety of things including the gas cap, emissions leak, or vacuum lines (they didn't seem to know much about it). They cleared it and it came back a few days later. It showed up not long after I started getting a brief clinking and clanking noise occasionally when I started it. I asked a mechanic friend of mine about the noise and he said it sounds like a typical busted cat and was probably what was causing the CEL. Then when I was 4 wheeling the other day though the light all of a sudden turned off and I haven't heard the noise since. I only heard the noise when I was starting it otherwise the truck ran great. I know my Mom’s 5.0 98 XLT had a light come on at 70K and she just needed a new cat, unfortunately I don’t know what her code was. Even though the light is out on my now does anyone know if I can still find out what the code it was on for before was?

 

[Robert]

There are several things that can cause a P0455 code. One of them is the fuel cap. The error means that your fuel line has a "gross leak". A leaking fuel cap, bad vent solenoid, leak in your fuel line or anywhere else can cause this error. Mine was caused by a leaking fuel cap even though it looked fine to me and had just passed our local emisisons check two weeks earlier. I spent the $10 for a new cap at Checker Auto Parts and kept the old one around for a few weeks in case the light came back on. If the light would have came back on, I would have returned the cap I bought. The light never did come back on and that was over a year ago. Take a quick look around your fuel lines and vent solenoid for anything obvious. If you don't see anything, then try the cap. It's only $10.

 

[ygu]

thanks rob, it turns out it was the gas cap, the last place I had gotten gas the attendant (live in jersey, don't have to pump my own gas) did not put the gas cap back on completly, more like just placed it there. I am in the process of doing 2 complete drive cycles and will let you guys know what happens. Thanks again

 

[VOATMJ1]

I have a "Check Fuel Cap" light. You guys don't have that, or did that come on and the CEL?

 

[Glacier991]

Nick..

OBD i and II store codes for a certain number of start cycles... for some reason the number 65 sticks in my mind. So you may be able to find out what your code ws if you are within some number of starts. Also, as a FYI on this subject of evap emissions codes, those will only be set within the first 30 minutes of operation as the Evap Monitor portion of the PCM is set to run it once certain conditions are met and only within the first 30 minutes of operation. This is not a continuous monitor.


Happy Exploring

Chris

 

[ygu]

I don't have a check fuel cap light, but that would have been cool. I wouldn't have to worry what was wrong with my car now....

 

[Nick26]

so what constitutes a complete drive cycle, 65 start cycles or is that totally seperate? cause i don't think i have started it that many times but the light has been off since saturday.

i'm not sure if i understand this right but what your saying about the evap emissions is that they would only get checked with in the first 30 mins of the car running and therefore making it impossible for that to have shut the light off? what are the conditions to make it run a check? im a little confused in general here too, is the evap monitor what monitors the catalytic converters or the vacuum lines or both?

sorry for so many questions im still just learnin...

 

[Glacier991]

Nick - No problem with the questions. That's what so great about this site, youcan ask almost anything and now and then you get a good answer <g>. Nothing's perfect.

To begin with a diagnostic trouble code, the thing that makes the light come on, is stored in memory for some period of time, even if the light is out. I think (repeat THINK) that is about 65 starts.

A drive cycle, in it's simplest form, is a cold start after at least 8 hours of sitting, and which runs the car in city type driving, and maybe some freeway.

Your computer has some things is monitors cocnsistently, and other things it tests now and then on some pre-determined basis. Evap emissions is a cannister that absolrbs fuel vapors, and at some point in the warm up it's purged into the engine to be burned. The computer checks on this system to be sure it's a "closed system" and if not, it will set a code. A gas cap is the usual culprit. This has nothing to do with the CAT, or vacuum. Let me suggest you check out this thread:


http://www.explorerforum.com/forums/showthread.php?s=&threadid=80692


another important thing to remember is that just because a certain code implicates a certain sensor does NOT automatically mean the sensor itself is bad. Other things can make sensors read "out of range". There is a thread on here called CEL myths, check that out too.

Hope all this helps...

Happy Exploring

Chris

 

[Glacier991]

Fore the original poster on this thread here is the Ford factory manual on this one )long I know but for a 1998)


The Evaporative Emission (EVAP) Running Loss System Monitor is an on-board strategy designed to detect a leak from a hole (opening) equal to or greater than 1.016 mm (0.040 inch) in the EVAP Running Loss system. The proper function of the individual components of the EVAP Running Loss system as well as its ability to flow fuel vapor to the engine is also examined. The EVAP Running Loss System Monitor relies on the individual components of the EVAP Running Loss system to apply vacuum to the fuel tank and then seal the entire EVAP Running Loss system from atmosphere. The fuel tank pressure is then monitored to determine the total vacuum lost (bleed-up) for a calibrated period of time. Inputs from the engine coolant temperature (ECT) sensor, intake air temperature (IAT) sensor, mass air flow (MAF) sensor, vehicle speed sensor (VSS), fuel level input (FLI) and fuel tank pressure (FTP) sensor are required to enable the EVAP Running Loss System Monitor.

NOTE:
During the EVAP Running Loss System Monitor Repair Verification Drive Cycle a PCM reset with key on, engine off will bypass the minimum soak time required to complete the monitor. The EVAP Running Loss System Monitor will not run if the key is turned off after a PCM reset. The EVAP Running Loss System Monitor will not run if a MAF sensor failure is indicated. The EVAP Running Loss System Monitor will not initiate until the Heated Oxygen Sensor (HO2S) Monitor has completed.

The EVAP Running Loss System Monitor is executed by the individual components of the EVAP Running Loss system as follows:

1. The function of the EVAP canister purge valve is to create a vacuum on the fuel tank. A minimum duty cycle on the EVAP canister purge valve (75%) must be met before the EVAP Running Loss System Monitor can begin.

2. The canister vent (CV) solenoid will close (100% duty cycle) with the EVAP canister purge valve at its minimum duty cycle to seal the EVAP Running Loss system from atmosphere and obtain a target vacuum on the fuel tank.

3. The fuel tank pressure (FTP) sensor will be used by the EVAP Running Loss System Monitor to determine if the target vacuum on the fuel tank is being reached to perform the leak check. Once the target vacuum on the fuel tank is achieved, the change in fuel tank vacuum for a calibrated period of time will determine if a leak exists.

4. If the initial target vacuum cannot be reached, DTC P0455 (large leak or no purge detected) will be set. The EVAP Running Loss System Monitor will abort and not continue with the leak check portion of the test.

If the initial target vacuum is exceeded, a system flow fault exists and DTC P1450 (unable to bleed-up fuel tank vacuum) is set. The EVAP Running Loss System Monitor will abort and not continue with the leak check portion of the test.

If the target vacuum is obtained on the fuel tank, the change in the fuel tank vacuum (bleed-up) will be calculated for a calibrated period of time. The calculated change in fuel tank vacuum will be compared to a calibrated threshold for a leak from a hole (opening) of 1.016 mm (0.040 inch) in the EVAP Running Loss system. If the calculated bleed-up is less than the calibrated threshold, the EVAP Running Loss system passes. If the calculated bleed-up exceeds the calibrated threshold, the test will abort and rerun the test up to three times.

If the bleed-up threshold is still being exceeded after three tests, a vapor generation check must be performed before DTC P0442 (small leak detected) will be set. This is accomplished by returning the EVAP Running Loss system to atmospheric pressure by closing the EVAP canister purge valve and opening the CV solenoid. Once the FTP sensor observes the fuel tank is at atmospheric pressure, the CV solenoid closes and seals the EVAP Running Loss system.

The fuel tank pressure build-up for a calibrated period of time will be compared to a calibrated threshold for pressure build-up due to vapor generation.

If the fuel tank pressure build-up exceeds the threshold, the leak test results are invalid due to vapor generation. The EVAP Running Loss System Monitor will pass and complete.

If the fuel tank pressure build-up does not exceed the threshold, the leak test results are valid and DTC P0442 will be set.

5. The malfunction indicator lamp (MIL) is activated for DTCs P0442, P0455 and P1450 (or P446) after two occurrences of the same fault. The MIL can also be activated for any EVAP Running Loss system component DTCs in the same manner. The EVAP Running Loss system component DTCs P0443, P0452, P0453 and P1451 are tested as part of the Comprehensive Component Monitor (CCM).

Figure 12: Evaporative Emission (EVAP) Running Loss System Monitor

 

[Nick26]

just for follow up sake i figured i would post because it might help someone else out down the line...

I never did get that check engine light checked out and it never came back on, might have been something simple like my gas cap loose or could have been from wheeling the day before when I got some water in my intake.

However, the clanking noise when I start I did solve. The starter was not retracting its gear after spinning the flywheel and was smacking into it unitl it got kicked back enough. It only did it when the car was cold cause the grease on the gear shaft would be to viscous until it warmed up. I'm thinking that the front pinion leak i had might have had something to do with it going bad because it was slinging gear oil all over the place including into the starter. either that or i might have gotten a little too much water in there.

 

[archer973]

It's good to find a thread that states a problem and then the correction is found and added into the thread. My wife just came back from a trip to town and said the check engine lite came on. I used Torque Light on my smart phone and found P0455 had been logged. Googled it, saw there was a lot about the gas cap. This thread also came back on the google search. When I told her about this thread, she remembered that she bought gas a couple of days ago and said maybe she didn't get the gas cap back on. A quick check and sure enough the gas cap was not seated. I will not clear the code. We will continue driving and see if it clears automatically. I will come back later to report.