I have a 1989 F150 4x4. The check engine light is on. It seems to run just fine, but I would like to know why the light is on. I know about the KOEO method of checking codes, but I do not know where my diagnostic port is. I have looked all over the cab of the truck as well as under the hood and I cannot find anything that even remotely resembles a data link connector. Where could the diagnostic port be? Is there another method of checking codes? Any help will be greatly appreciated. Thanks.

 

It's on the drivers side fenderwell behind the air box on my '88. It hangs in a plastic cap next to two realys.

 

I think it's inside the engine bay, anyway if you use the paperclip method the light will blink in the dash.

 

Yeah it clips right onto the fender and is next to the hood hinge. Cant miss it. It can be a pain to pull that little connector off without snapping it tho.

 

Yep. There it was. That explains why I couldn't find it. The previous owner must have broke the clip because it was just laying amongst some other wires and was hidden. It looked like some of the other wires so I must have just over looked it. Thanks for all the help. I will be trying the KOEO method tomorrow after work and see whats up. Thanks again.

 

How long has the CEL been on?

I am not real sure about the 89 models but on the 87-88 models codes will not trigger a CEL. I don't even think Ford installed a bulb in the cluster for the CEL.

I am not sure what year Ford integrated the CEL as a warning, but I was thinking it was 90 or 91.

As far as pulling codes, here is my best friend for my OBD1 truck

Equus Innova 3145 OBD-I Ford Scan Tool

By far the easiest and cheapest way to check for codes on these trucks.

 

Ford Fuel Injection » How To Run a Self-Test Have a read here. Should help.

 

Thanks to everyone who helped me locate my diagnostic port. Now that I have the codes, I am having a little trouble understanding 2 of them. I got 4 codes, one code occurred twice. The codes were 31(EGR Positioner Sensor below minimum Voltage) 67(Park/Neutral Position switch circuit open - A/C on during self-test) 29(Insufficient Input from Vehicle Speed Sensor) and 31 again when it was displaying the stored codes. I know what 29 is as my speedo cable is broke and I haven't gotten around to fixing it. The truck has a 5 speed so I'm having trouble understanding code 67, isn't that for automatics? My truck still starts and runs just fine, I haven't had a problem with it. And code 31 to me sounds like a bad EGR valve, but the descriptions of the codes I found weren't very good. Any ideas as to what needs to be looked at/replaced?

 

It definitely isn't wired from the factory, but the computer can still turn on the light if it is wired.

If you have a six cylinder, you will have to hold the clutch pedal on the floor to keep this code from coming up during the self test.