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False engine light

I have an 02 Ford Taurus SE 107,000 mi.

Had a fuel pump and cam sensor replaced (the check engine light came on when the car was stalling, etc. due to these problems).

A week or so after the repairs, the engine light came back on. It was right after I’d gotten gas so they did the gas cap check, etc. The dealer said they couldn’t locate the code that was showing. He turned the light off and said not to worry about it, but I could bring it back for more testing if it came back on. Said they couldn’t test everything since the tank was full…? Days or weeks later the light returned. My husband disconnects the battery once in awhile. It stays off for some time but always comes back on. Hate to return to the dealer as we were charged before and nothing was fixed. We are going to be selling the car and want to disclose any problems. So what’s up with the light?? Thanks for any input.

When it comes on again, take it a parts store, AutoZone, something like that and they will read the codes for free. if the light is on, there will be a code. Then post back here with the code…

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here. Once we have the code, we can start considering what needs to be done.

Without know what the code was it is difficult to blame the dealer, although I believe they should always give the owner a written report anytime they read a code.  It does sound like the code may mean more than one things and it make take some testing to determine which one is the problem. 

Don't make the mistake of finding out that the code relates to say an O? sensor and then have someone replace the sensor.  Although it might indicate a bad sensor, they don't put sensors just to be checked, the sensor is measuring the exhaust and the code means the reported value is not what should be expected.  That could mean a bad sensor or something causing the sensor to report a problem with the exhaust gases it is monitoring.

Aha…pulled out the repair order from dealer…It says KOEO PASS/P0442 POSS FUEL CAP

Is it just a coincidence that just 11 days prior to having this chronic engine light problem, they had replaced the fuel pump and cam sensor?

Just in case it might apply we had a voyager with a cel problem, it ended up being a bad pump that kicked on every x amount of miles to check pressure in the fuel system, and since the pump was bad the cel was inevitable. Only 2 different dealers to fix that one, under warranty thank goodness.

P0442 is a leak in the gas evaporation system. What I’d really like to know is what the codes were that led to a new fuel pump & cam sensor. I surely hope it wasn’t this one - but probably not since this one is unlikely to ever lead to any problems you’d notice.

It is tru that the first thing you do is check the gas cap. If that isn’t it replacing the gas cap may be recommended. But it is also wise to check the vacuum hoses in the evaporation system.
In short, there is a system that collects gasoline vapor & sends it into the intake to be burned rather then letting it vent to the atmosphere. There are some (probably) black rubber tubes running from your gas tank to an area under the hood with a charcoal canister where the gas fumes accumulate & some more tubes and other gadgets that move the fumes into the intake. One of those rubber hoses for moving the fumes may have a leak - and it doesn’t have to be large.

Checking those hoses isn’t easy, so I’d start with the gas cap - which is easy. Presumably the dealer did whatever could be done with the existing gas cap already, so find a new one, clear the codes & see what happens. You should be able to accomplish both for cheap at most auto parts stores.

I would suspect that the fuel pump replacement disturbed or broke something in the evaporative emission system (of which the gas cap is part). The fuel tank usually needs to be dropped to replace a fuel pump, which means disconnecting parts of the evaporative emission system. If the fuel tank was removed or lowered in the process, whoever did the fuel pump replacement owes it to you to fix whatever they did to the EES. It may be as simple as a loose wire or a hose that wasn’t properly reconnected.

That code can come up if you regularly overfill your gas tank. You should always stop at the first click of the handle and not add anymore after that. But since this has occurred just after maintenance on the fuel system, I would suspect that one of the vent lines was disconnected and not reconnected.

On some vehicles, some of those lines are on top of the gas tank and very difficult to check. The dealer probably doesn’t want to drop the tank just to check for a loose line, but they should not charge you for checking their own workmanship.

I second the idea that something got broke during fuel pump install.