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The check engine light is on in my 1989 Ford E250 Econoline van. I heard from a mechanic (who changed my oil) that there's a "key cycling" process that will cause the light to flash in a certain pattern that encodes the cause of the check engine light.

How does "key cycling" work and where can I find a decoding scheme so I can tell what the problem is?

EDIT: Based on Jaime's answer, I consider the second half of this question to be answered. However, I still haven't gotten the key cycling to work (even after trying Dave's suggestions).

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I am not sure how it would be like on 1989 Ford E250 but on Dodge 1998, this is like this

  • Turn the Ignition Key to on, turn it back off in quick sucession
  • Repeate the above step 2 more times (total 3)
  • On the forth, leave the ignition switch key on ON

Now the Engine Indicator light will start flashing. Five short flashes, followed by a pause and then five short flashes, followed by pause and then five short flashes.

Let say you got 4 flash, pause, 3 flashes, pause 5 flashes, that indications engine code 435. You will look this code for you car and it will indicate the problem part of your car.

If your car has problem in more than one area, these sequence will continue untill all codes are covered. You will need a pen and paper to note the code down.

I am not entirely sure if your 1989 vehicle will have this system because. I believe the computer got started in 1998 vehicles and later.

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Thanks. I'll try that. – Quinn Culver Nov 20 '11 at 23:50
Can't vouch for Ford or others, but this also works on a '94 Jeep Grand Cherokee. It may just be a Dodge thing though, since they make Jeep as well. – Iszi Nov 28 '11 at 8:24

Reading the codes will do you no good unless you know what each one means.

If you go to Autozone (or something similar) they will usually read the codes for you for free. There is an EEC-IV Test Port connector somewhere in the engine compartment. They will know where.

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Is there somewhere (preferably online) I can find out what the codes mean? – Quinn Culver Nov 22 '11 at 12:36 – Jaime Nov 22 '11 at 16:56
Thanks. Do you know anything about key cycling? I tried @Dave's suggestion, but it didn't work. – Quinn Culver Nov 22 '11 at 21:17
This should work for any ford obd 1 vehicle: I've only ever used the cheap code tool that just beeps at you. But, this should help. – Jaime Nov 22 '11 at 21:37
Autozone and similar generally won't read codes for OBD-I systems. At least, that's how it is in my area. – Iszi Nov 28 '11 at 8:25

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