what do these codes mean?

[HappyGilmore]

i hope i am posting in the correct forum. feel free to move if not.

i did the self test on my 94 explorer sport because it has a somewhat rough idle and gets bad gas milage. i clean my MAF every couple oil changes (which helps) but i ran the self test to see if there was anything else because it still isnt perfect and the gas milage still sucks. heres the codes i came up with:

KOEO 335

CO 543

can anyone tell me what these mean?
thank you

 

[amberone]

Check your fuel pressure

 

[live2_4x4]

O.K here goes my Haynes manual lists:

335= EGR sensor voltage out of range

543= fuel pump citcuit open; battery to pcm

Now I'm no expert but I believe the egr valve or sensor could have to do with your rough idle problem, but my guess is that the fuel pump circiut being open sould have other symptoms.

Hope this helps
Glen

 

[MrShorty]

live2_4x4 is on the right track. A KOEO 335 could certainly be part of a bad idle and other driveability problems. As a KOEO code, it has to be an electrical fault, which means it can't be the EGR valve itself. PFE/DPFE sensors on these frequently seem to fail. If the wiring between the PFE/DPFE checks out OK, then it's probably the sensor that's bad.

As for the CM543, this could be an old code (clear CM codes by pulling jumper during KOEO/CM code output, drive, and see if this code returns) or it could indicate an intermittent fault in the fuel pump and/or fuel pump monitor circuits.

 

[HappyGilmore]

ok thanks guys guys. ill check that stuff out.

 

[HappyGilmore]

ok so i decided not to be lazy.i did an indepth search on this forum, looking through many many threads. this is what they said:

1. PFE/DPFE sensor is also called an EGR position sensor
2. you can get that sensor for 50 bucks at autozone (i checked and they dont carry it here, NAPA autoparts wants $97 for it!)
3. ignore the 543 code
4. the EGR sensor wont affect my gas milage by repacing it (but my idle isnt that bad. my main problem is my gas milage)

what do you guys think about that? is that stuff true?

what about my oxygen sensors how do i know they are bad, even though no codes show up for them?

should i replace my fuel filter? (ive had the car over 2 years and ive never done it. doubt it was done by the original owner.)

 

[live2_4x4]

O.K I'll help where I can

#1-True to the best of my knowledge the two terms seem to be almost interchangeable.
#2-I can,t help on price(i'm a Canadian EH!)
#3-I don't think any code should be ignored Try having the codes cleared and see if it re-occurs.
#4-The EGR may have a small effect on mileage because it in effect reports to the engine control system which controls injector pulse, timing etc(however HOW much effect I don't know)
As for your mileage how bad is it? explorers are not exactly the best for mileage...as we all know.

If yours is below average, Have you checked the basics, air filter, clogged fuel filter, plugged injector, sticking brakes?

I replace my fuel filter frequently, (25,000kms) The Haynes manual says it is a lifetime filter and should not need replacing but my work van has 200,000+kms on the orig pump with frequent changes.

As far as your idle goes have you cleaned/replaced the IAC (probably the #1 cause of rough idle in explorers)
Keep at it.... You will win
Glen

 

[HappyGilmore]

well im getting 13mpg. i guess its not that bad, and i know my engine is somewhat old and tired with 125,000 on it. 16mpg i think is reasonable. am i expecting too much with that expectation? (city driving)

ok so ill change my fuel filter (10 dollars, no biggie) then clear the codes.

my KKM was cleaned not long ago along wth my MAF. so im good there. brakes i know aren't sticking (i spun them the other day when the car was jacked up.) all thats left are the injectors..ill do a search on how to check those. oh yeah and my tires were just replaced so hopefully the shop filled them to spec. ill double check. (BTW theyre stock size 235/75/r15)

man an IAC is like 98 bucks (keep in mind im 17. ha ha)....i found an article on how to test that with a volt meter so i hope its still good. (then again if it fixes my problem maybe i wont be so bummed.)

thanks for your help.

 

[live2_4x4]

Do a search on cleaning your IAC, often you can pospone buying a new one (for a little while anyway) by cleaning it. See if this helps any. btw 16mpg should not be unreasonable in an explorer but remember (since you're only 17 ha-ha) that actual mileage depends ALOT on how you use the go pedal.
Glen

 

[HappyGilmore]

yeah i just cleaned it today, i found the thread. it didnt get all shiny in there but some junk came out. i dunno how clean it was supposed to actually get. then i put sea foam in and reset the computer. it runs a lil better i guess. before i cleaned my MAF i could watch the tach fluxuate, but now i only hear the fluxuation from my loud 40 sieres(sp?), since the fluxuatuion is so much less now. the tach is steady.

i understand that gas milage also depends on your driving habits but the funny thing is, is that one time i tried to see how many miles i could drive on one tank, so i drove real easy on the gas and my milage was pretty much the same. i had maybe a 20 mile gain. (i guess that is a 1MPG gain so i cant complain too much)

after i drive for awhile tomorrow and the computer relearns everything i will pull the codes again and see what comes up. my tank is almost empty so ill fill it up, then see how my milage goes.
thanks for your help live24x4