Cheapest way to check "check engine light" code

[sgunes]

My 2003 Expedition, EB, 4x4, 97K miles started to have either blinking or steady CEL. It idles roughly and seems to have less power. I wanted to have an idea what is wrong before I comparison shop between the Ford dealerships and a local mechanic. I don't quite trust the dealerships.
Do parts stores offer to diagnose the code or is there any other free/cheap way to find out what is wrong?
Thanks.

 

[FordandPolaris]

Yeah O'Reilly, Autozone, and NAPA all have code readers for free. Start there. Post the codes you get back here, depending on what it is, you may be able to just fix it yourself and save a good chunk of change.

My money is on a misfire condition with one of the cylinders. That is the only time I have had the CEL start blinking at me personally. Probably going to have to replace a coil pack and spark plug. Get the codes before purchasing anything though.

 

[ELVATO]

At 97k, it was time to do a plug change anyways. If you order online, it shouldn't be too bad. COPs, are going to be a bit more pricey, especially if you buy local.

I'd also inspect the boot of the COP. It might just be cracked/ripped and letting some water in. If you have some dielectric grease handy, you could take off each COP, clean, inspect, and apply a new bead. A new boot is way cheaper than a new COP.

 

[Oefootball_70]

Cop?

 

[toms89]

Cop?

A law enforcement officer.


Or

Coil over plug
Coil on plug

 

[Odimus]

Harbor Freight carries a decent code reader...

 

[sgunes]

I went to O'Reilly and they pulled the code for free.
I have: P0304 Cylinder 4 misfire.
I notice that the engine runs rough and lacks power.
What's the best/worse case scenario?

 

[FordandPolaris]

I went to O'Reilly and they pulled the code for free.
I have: P0304 Cylinder 4 misfire.
I notice that the engine runs rough and lacks power.
What's the best/worse case scenario?

Well if you pay someone to do it, it will be a couple hundred I'm guessing. That unfortunately is going to be the very back cylinder, and is not very easy to reach. Couple of universal joints and some extensions makes it possible, but if you don't work on cars much it might be easier to pay a guy. I would say that it is safest to do both the plug and COP since it is so far back there and not worth doing the job twice. It is going to be the back plug on the passenger side.

 

[Stangy89]

$14 OBD-II Bluetooth adapter from Amazon
Free Android App called Dash Command
Gives you access to view and reset codes and live telemetry of the vehicle.

 

[sgunes]

$14 OBD-II Bluetooth adapter from Amazon
Free Android App called Dash Command
Gives you access to view and reset codes and live telemetry of the vehicle.

Right now I have IOS but may switch to android depending on the features of the upcoming new iphone.