Mystery EEC Code

[ChrisHelvey]

Hi all,
I have a new-to-me B4000, 126K miles, that the check engine light comes on and goes off fairly regularly. Loses power a bit sometimes but not terrible. If I floor it (which I think puts the system into open loop mode) it kicks back up to high power and runs smoothly.

After clearing the codes to start with a clean slate and then driving about 50 miles, I retrieved the codes:
117 - Book says "Coolant Temp circuit below voltage.." So I will replace that.
217 - Book says "PCM detected coil 3 primary circuit failed (1994 only) I'll look in to that.

and then...the mystery...
Code 317. Yes, I checked it four times - it's a 317.

Nothing in my Haynes book on the Ranger or in the Haynes computer code book.

Anyone have a more comprehensive manual or know what the heck this is?

Thanks for the input.

Chris

 

[almostclueless]

1. How did you retrieve the codes?

2. Haynes manuals are pretty much only suitable for toilet paper substitute. Factory manuals are the best (ebay) and the bigger chilton's manuals aren't too bad.

3. A quick look on the web leads me to believe 317 might be something about the system that pumps air into the exhaust.

4. Don't just instantly assume the coolant temp sensor is the cause of that code, though replacing it may be the easiest way to troubleshoot (but not guaranteed).

5. A coil primary circuit failure can very easily make an engine run quite bad, especially on a computer controlled vehicle. Again, it may not be the coil itself.

6. getting a good Ford dealership shop to completely diagnose the causes of multiple problems might be cost effective.

 

[MAKG]

Umm, "below voltage" faults are almost always NOT the sensor.

Usually, it means the sensor is unpowered. But a comprehensive test of that circuit is called for.

Codes test circuits, not sensors. Frankly, if you don't know the difference, you aren't saving money by avoiding the shop.

The coil 3 circuit requires a similar response.

You also need to draw distinction between hard and soft codes, and engine-running vs. engine off. And THAT part IS in your Haynes book.

 

[smokey]

317=Thermactor Air System problem – air flow not bypassed (vented to atmosphere) during Engine Run Self-Test.

 

[MAKG]

A 1994 4.0L has a thermactor?

That sounds more than a bit odd....

 

[almostclueless]

Not really, when you consider that for quite a while during the EEC-IV era they injected air into the cats......maybe they called it thermactor, just not injected into the exhaust ports.

 

[MAKG]

Yeah, but "quite a while" was 1983-85 or so. The only thermactors I've seen have been attached to 2.8Ls.

 

[ChrisHelvey]

What I have learned from this thread so far, and my comments:

Haynes manuals are only marginally useful. (A somewhat helpful comment in that investing in a better manual could be worthwhile.)

I jumped to concluding a sensor is weak and I should do a more comprehensive check on the wiring. I can do that. Yes, I do know the difference between testing circuits and sensors. And yes, I do know what a circuit is. Since the manual only has replacement procedures, I will look at the schematic to see if I can make some sense out of it. If anyone would like to contribute any helpful advice here, other than telling me to take it to a dealership, I will appreciate it.

Same with the coil - I know how to work a meter....or a scope if necessary.

The 317 code may have to do with the "air injection" system, which this engine definitely does have, looking at the air pump and the big metal pipe that runs from it to the exhaust manifold. Thank you for that lead - it gives me a place to start.

Some info:
I retrieved the codes using the procedure in the manual for the KOEO and engine running, and I did the wiggle test procedure too, while wiggling any sensor or harness location I could put my hands on. No new codes doing this. (I cleared it first.)

I have an OBD-II scan tool, but see no way to use it in this circumstance.

Thanks

 

[Donnie strickland]

If you haven't already done so, your Haynes manual tells you how to check the coil with a VOM.

 

[MAKG]

Haynes manuals are great for things like brake jobs and engine inspection. They suck for emissions.

The Mitchell books are sometimes available at the library. Those are MUCH better. Every code has a pinpoint test, which would be a very nice starting point.

 

[ChrisHelvey]

Thanks for the input.