Service engine soon light is on

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 is going on.

Follow this guide to help find the problem code:

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

Please let us know happens so it will help others.

First of all, you are confusing the check engine light with the older "maintenance required" light that was used in the 1980's 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.

Change the wiper motor and brake light switch too as long as you are going to guess. 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 are 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 are 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.

Boy, I sure sounded sarcastic. Sorry about that. Do not 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 is not 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 is 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.

Seven years old is not time to retire it. I have three newer vehicles, (I mean newer than 1988), but I only trust my 1988 rusty trusty Grand Caravan to get me home after numerous cross-country trips. I regularly drag a tandem axle enclosed trailer that is bigger than the van, and it is only had one transmission fluid and filter change in its life of 225,000 miles. It did not get me home for the first time in its life a few months ago due to a bad ignition coil, but I had eleven months of warning with intermittent stalling.

To add to the abuse, I have not 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 am feeling generous! I would not dare treat my other cars like that.

The point that I am 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.

Well the proper way to do it would be to hook a scanner up to the data link connector port (below the dash, trapezoid shaped, see attached image) and have the scanner erase the code(s). You might as well get the trouble codes and write them down so we can diagnose the issue. You can buy an OBD2 scanner from Amazon or eBay for pretty cheap, or you can go to AutoZone, Advance Auto, or O'Reilly Auto Parts and have them scan and clear it for you. They do this for free. Also, here is our guide on the check engine light, which includes how to scan for codes: https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

The other option would be to disconnect the positive battery cable and touch it (the disconnected cable) to any ground or the negative battery terminal for about ten seconds. This will ground out any residual energy in the system and reset all of the computers (including the one with the codes).

Its just coincidence it came on at 50 k. First we need to find out what the codes are. Autozone will scan the computer for free. Have this done and get back to us, dont wait just in case this problem might still be covered by factory emissions warranty. Hope this helps

Good afternoon.

Have the codes checked and again and get a print out and list them for me.

There is no such thing as a kill switch. There is an inertia switch for accidents and roll overs but since your car runs, that is not the issue.

Roy

Hi there,

I have found with my snap on scanner that in some instances not all codes are read, although this is a very high quality unit, it dose have its hiccups, you may have to get a ford scanner to read this code, will the snap on unit do a code clear? May be do this and let the code re set and then re scan, I have had some success doing it this way.

Mark (mhpautos)

It is a check engine light. You need to have the computer scanned to identify where the problem is coming from. Most parts stores will do it for free.

Have that done and let me know what you find.

Joe

Hello,

No it is nothing you have done. Most likely if your vehicle is running fine thenmost likely it is an O2 Sensor (Oxygen Sensor). You can go by your local auto parts store and have them pull codes, most will do it for free. Get the actual number code and post here for farther diagnostic help.

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