Mechanics

SERVICE ENGINE SOON LIGHT IS ON

2004 Ford Explorer • 6 cylinder 4WD Automatic • 100 miles

I have a 2004 ford explorer XLT the "service engine soon" LIGHT keeps coming on. I UNDERSTAND this light may come on when the vehicle reaches a certain mileage. My vehicle has reached 125k. And this light has been coming on/off around that mileage area.I disconnect the battery for several minutes and its off. After a few days it returns.
i replaced everything in regards to electrical
starter
plugs
plug wires
egr valve
belt
belt tensioner belt pulley
alternator.
what else could this be. Thank you in advance.
Avatar
Mariob539
April 17, 2011.




http://www.2carpros.com/articles/service-engine-soon-or-check-engine-light-on-or-flashing

Have the computer scanned for code/s-you have a problem within the engine management system that caused the CEL to turn on-This is your starting point of diagnosis,finding out what's going on.

Tiny
Rasmataz
Apr 17, 2011.
So your telling its not engine problem? Maybe oxygen sensor- that was never changed

Tiny
Mariob539
Apr 17, 2011.
First of all, you're confusing the Check Engine light with the older "Maintenance Required" light that was used in the 1980s with truck emissions systems. The Check Engine light means the Engine Computer detected a problem and set a diagnostic fault code in memory. You erased those codes and lost that valuable information when you disconnected the battery.

Most of the parts you guessed at and replaced have nothing to do with the Check Engine light. Namely, the starter and generator have nothing to do with the engine sensors and emissions system. As rasmatz indicated, having the fault codes read is the place to start. Many auto parts stores will do that for you for free. They will get you into the right circuit or system with the problem, not necessarily the defective part.

Caradiodoc
Apr 17, 2011.
Change the wiper motor and brake light switch too as long as you're going to guess. It's apparent you're not aware that there are a dozen computers on your truck all with multiple sensors and switches. Two computers are involved in blowing the horn. A computer is involved in running the power windows and locks.

There's over a mile of wires in your truck. Any one of them can rub through and short out. Computers commonly fail. Sensors can feed incorrect information to those computers. This is why mechanics must continually go for update training. Every time you replace some random part, you are introducing a new variable that can confuse multiple computers.

You're not going to solve this by replacing parts. Start by having the fault codes read. That will save you the expense of all the unnecessary parts

Caradiodoc
Apr 18, 2011.
Ok-ok.I was just guessing and replacing parts randomly.I did this cause it was time to rreplace before they went and all replaced with ford parts.I am going to the store today and get diagnosis. Thanks to all.

Tiny
Mariob539
Apr 18, 2011.
Boy, I sure sounded sarcastic. Sorry about that. Don't do the "random" thing. That is the most expensive, least effective way to diagnose a problem. First of all, there are some parts that have a history of almost never needing to be replaced. Doing so is money wasted, but more importantly, everything you do or replace adds another variable to the problem. Some sensors require precise air gaps to work properly. If one isn't set right, you could now have two problems. Also, many resistance sensors such as throttle position sensors and any temperature sensors will never have the same resistance between any two of them. The Engine Computer learns their characteristics by comparing their readings to other sensor readings. For one example, the computer knows that the coolant temperature sensor and the intake air temperature sensor have to be reading the same temperature after the engine has been off for at least six hours. When it sees a different resistance from one of them than it expects, it has to figure out which one changed and put that new set of values in memory. That will not occur if it thinks there's a problem with the other sensor so you could introduce a running problem just from removing a good sensor and replacing it with another good one.

The best approach, since the Check Engine light was on, means at least one diagnostic fault code has been stored in the Engine Computer and having them read will get you into the circuit or system with the problem. There might not even be a defective part. You could have an EGR, (emissions) tube that is plugged with carbon, a leak in the fuel supply system that is letting vapors evaporate, a sensor problem, or a sensor could be detecting a problem. Someone here will be able to give you direction once we know which fault codes were stored in the computer. Many auto parts stores will read them for you for free.

Caradiodoc
Apr 18, 2011.
LOL--thanks for info going to a auto store this afternoon.I will say this. My ford has 125K on it. Its 7 years old. But looks show room condition. The tuck took me home everytime! And I went allll over the place. Even in the mountains and it helped me drag my friends car out. Upstate NY. If it is something serious and costly. It may be time to send it to its final resting place. We will see. AND THANK YOU FOR THE INPUT! ALWAYS APPRECIATED!
Mario

Tiny
Mariob539
Apr 19, 2011.
Seven years old is not time to retire it. I have three newer vehicles, (I mean newer than '88), but I only trust my '88 rusty trusty Grand Caravan to get me home after numerous cross-country trips. I regularly drag a tandem axle enclosed trailer that's bigger than the van, and it's only had one transmission fluid and filter change in its life of 225,000 miles. It didn't get me home for the first time in its life a few months ago due to a bad ignition coil, but I had 11 months of warning with intermittent stalling.

To add to the abuse, I haven't pulled the oil drain plug in over eight years! I add a quart about every 1,500 miles and change the filter, ... Oh, ... About once every three years, if I'm feeling generous! I wouldn't dare treat my other cars like that.

The point that I'm not making is I would rather see someone fix an older car vs. Buying something new. The engineers have figured out too many ways to cost us money with their current products and I refuse to have any part of it.
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Caradiodoc
Apr 19, 2011.

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