Check Engine but no codes?

[truckguy94]

The "Check Engine" light comes on on my '94 F-150 4 x 4 (110,000 km), and when I had it checked out today, it showed no codes stored at all. The light was coming on a lot for a couple of weeks. The mechanic I go to did not have the connection for the older trucks, to check the code, so he suggested disconnecting the battery and resetting everything, just to see if it was false code, because the truck is running very well.

The light came on again Saturday, and again yesterday (Monday), so I took it in to a larger shop and, as I said, he found nothing stored in the computer. The truck runs really well, though the mechanic today said it was running only slightly rough, but hardly worth mentioning. He did check a couple of plugs but they are ok....certainly it is not in need of a tune up, he said, and the gas mileage is still in the 20- 21 mpg range (mostly highway).

The light comes on after it has run a while...20 minutes if on the highway, and it only comes on once in a while in the city, as the trips are shorter.

Is this just a dummy code? Or has someone else had a similar problem? Plug wires are new, apparently, and when I bought the truck 3 months ago, the mechanic said it had had a tune-up not that long ago. No stumbling and no obvious loss of power on the highway. Gets regular maintenance and the PCV was just changed on the weekend (what an awful location for a PCV).

I had a '92 Flareside for 13 years and it was always good at capturing codes, even two weeks after the fact, so I am not sure if false codes are common or not?

I don't know if this means anything or not but someone told me that a gas cap not positioned properly will cause some codes on some trucks. When I bought my truck, I had to replace the front tank (leaking)...the prev owner just ran on the back tank....I just went out and checked, and while the caps are secure, the little flap, where you insert the nozzle to pump gas, is missing on the front tank.

Bill

[lynger]

the little flap, where you insert the nozzle to pump gas, is missing on the front tank.

I,m no mechanic, but that could be the cause....the gas cap being tight has something to do with pressure in the system I believe. So maybe the missing flap is leaking whatever pressure it builds causing your problem engine light. My 2 cents anyway.

Josh

[Cooker]

Also if it's an older gas cap and it's not sealing properly, the light will come on. Could be a cheap fix, pick up a new cap... put it on drive it for a bit and see if it shuts off.

[fordtough.ca]

Also if it's an older gas cap and it's not sealing properly, the light will come on. Could be a cheap fix, pick up a new cap... put it on drive it for a bit and see if it shuts off.
Didn't Ford had a problem with some of them?????

[truckguy94]

thanks, I will try a new gas cap today...
Bill

[mitchbtu]

Im almost wondering if maybe there is just a weird sort of short with the light itself. If the light comes on that means a code has been thrown from a sensor, yet you show no codes... I would think if it is the gascap it would still throw a code... Let us know the results of the gascap replace.. Im really curious..

[truckguy94]

yeah, the mechanic showed me the reader: nothing (3- 4 different screens)...he went on to pull a couple of plugs ... he said there was some slight odd burning on the one plug but nothing serious enough to want him to blame the plugs at all, and the other tune-up parts are reasonably new... I did not get a chance to get gas caps today, but will do so tomorrow...the rubber seal on one cap does look dried out certainly, but I was running on the other tank and still got the light......getting 16 mpg city driving so the fuel consumption is not out of line, and the truck is running smoothly ... truck gets 19- 21 on the highway, usually closer to 20- 20.5 range... as a precaution, I called a dealer that I have been told is very reputable, and will have them check the codes next week, if the fuel cap thing does not pan out.

The mechanic that read the codes had a very new looking reader so I wonder if it is not the right type, as was suggested earlier.... I specifically asked the dealership if they had a good reader for a '94 model, and he said they did.

[Northern Supercrew]

If i remember, the older fords have 2 kinds of codes. hard and soft ones. the hard ones stay in the memory and will illuminate the CEL. The soft ones are not stored and the CEL may not come on. Hope i'm giving you some accurate info. keep us posted with the findings.

[truckguy94]

one of the guys on F150.net mentioned he had trouble getting codes off his car ('93) which used the same early code system...finally was told it took a specific type of reader to pull it off properly and the code was for a sticking EGR....

...in the meantime, I changed the gas caps this morning...heading over to Manitoulin Island early tomorrow, so if the light is still going to come on, I will know it. I think I will check with the dealer again, if the light is coming on...I will be stopping at a real good Ford dealer about an hour from me, on the way to "the Island", next week, and I'll find out if I should leave the truck running when I get there, if the light is on, just to ensure we get a code, if there is one to get...lol.

If the truck was higher mileage, I would not be so fussy, but it has only 110,000 km (under 70,000 mi), and it is otherwise very, very nice condition for a nearly 15 year old truck.

And thanks to the folks who run this board...I have only used it a couple of times since hooking up a few months ago, and the info you guys pass on is really excellent...

I am also glad to have another F-150. My first F-150 was a brand new '90 XLT Lariat Nov. 89) 2 wd, loaded with every option, and it was a beauty. The second was a '92 Flareside 2wd, also loaded, bought as a demonstrator in Nov. '92 (too good a deal to pass up; I wasn't even looking for another truck at the time)...I had it 13 years and 300,000 km...had swapped in 2 new fenders (minor rust), and was gonna change the doors, too (also minor rust), but my father hit black ice one day in November and that was the end of the Flareside...lol...engine was not even using oil when it was totaled, nor was the tranny acting up.

The current F-150 has the chrome bed rails off my '90 F-150 (my father bought the '90 and added a cap, and saved the bed rails 16 years til I grabbed them)....I also have the spare tire out of the '92 Flareside (it, the tailgate, and the grille were the only things not destroyed when the Flareside rolled...lol)

And a PSA about seat belts...we were wearing our seatbelts when the truck rolled..my father had a minor scratch on his head; I was uninjured in the initial impact; that is it... in the confusion of the truck being upside down in a shallow ditch about 6' below the road surface, I broke my arm when I got wedged between the seat and the altered roof line, not realizing what was going on...lol... the roof had been karate chopped between us, right to the dash, but it had not crushed the roof where we were sitting....
Bill

[fordtough.ca]

You guys where lucky
Hope the cap will work for you
Did you try to borrow a reader from Canadian Tire

[truckguy94]

I bought the caps today...the front filler spout has some superficial corrosion and the cap itself seemed to have a dried out seal....for the first time this week, the light did not come on, on the way to work, but realistically, I will know better after I run over to Manitoulin Island (2 1/2 hours) on Friday morning.

[fordtough.ca]

Have a great trip, and take allots of pictures :)

[taisa899]

Im almost wondering if maybe there is just a weird sort of short with the light itself. If the light comes on that means a code has been thrown from a sensor, yet you show no codes... I would think if it is the gascap it would still throw a code... Let us know the results of the gascap replace.. Im really curious..

I was thinking the same thing

[truckguy94]

light came on after the gas cap replacement, eventually, so I will see the dealer Thursday, and see if he has better luck finding a code that will register...

[truckguy94]

I went to a Ford dealer in the area but it turns out the guy was just covering for the service guy and should have verified they had an old code reader. They did not. The service manager suggested I check here in the city as a guy told him an independent definitely could read the codes. I checked with a long time independent in the city and he said he specifically kept one of the old code readers and even had a couple of guys who could pull the codes manually, so they will check it out Friday morning.

Even with the light still coming on, mileage to Manitoulin Island (2 1/2 hour ride) and 4 days of general use over there, I averaged over 22 mpg, my best mileage yet. The thing is, this big old 4 x 4 is most comfortable running about 80- 90 km/h...it will go faster, but you have to be on the gas pedal a lot...lol...so keeping the speeds down does help.

[SKRWZ]

This may help you out a little

http://fullsizebronco.com/forum/showthread.php?t=44736

and this as well

http://www.broncodata.com/tech/codes.htm

[truckguy94]

So, I got the truck in this morning to the independent repair shop, long established in Sudbury, with a very good reputation.

Here is what they pulled, with an old code reader they kept around:
- fault codes 172/ 334...
* EGR Valve replaced
* EGR Position Sensor replaced
* Oxygen Sensor replaced

- they were also concerned about possible vacuum leaks, but when they installed the one sensor, it reacted properly so they ruled out possible vacuum leaks (I am not very mechanically inclined, so I might have messed up that explanation a bit)

Truck was running pretty good to begin with so this was not a "miracle cure".....lol...but I am not getting the "Check Engine" light on anymore, and was able to peel the black tape off the dash, permanently.....

Bill

[Northern Supercrew]

that's great to hear Bill. It's funny the egr and 02 didn't give a code. but you got it figgered out and that's the main thing.

[truckguy94]

they pulled the codes right away at the independent shop, but the service guy said they had one of the old readers and had purposely kept it for situations like mine....

[fordtough.ca]

Congrats good news
They just changed all 3 as it may be a combo fault code

[truckguy94]

yeah, initially, they were worried about vacuum leaks, given the age of the truck, but the oxygen sensor reacted properly immediately, so that apparently meant there were no leaks and they were pleased.

[fordtough.ca]

Lucky, How is the truck running now?

[truckguy94]

the truck was running well before the check engine light had started to come on, though in recent days it was running a wee bit rough.... it is definitely smoother now, and maybe not seeing that bloody light come on all the time, makes the driving a bit more comfortable...lol .... incidentally, the name of the independent is Jim's Automotive in the south end of Sudbury, if you happen to live in the area and/or be visiting the board...they have a very good reputation in the city for the quality of their work. I have dealt with them before for a replacement gas tank, and both times they were thorough and took the time to explain what they did (I am no mechanic, so that helps...lol)

[fordtough.ca]

Its nice to have a mechanic like this
I'm glad you are happy :)