CEL Presence

[mp470]

Hi again all, truck was parked for the long winter.

What year did the first CEL appear? Mine is a 1985 and I wonder if a bulb is burned out or if it's simply not installed.  I found on one of the usual difficult to read wiring diagrams, 'to MIL IND' starting in 94-95, and prior to that it only seems to give a general ' to warning indicators'.

[Gary Lewis]

In this response Bill said "I also found that the CEL or MIL wasn't on even the first few years of the EEC-IV after the 1986 models."  And to back that up I don't find an MIL or CEL shown in the 1986 EVTM - although I might have missed it even though I looked twice.

[ctubutis]

I believe 1987 was the first year of a CEL/MIL connected to the computer.

[Gary Lewis]

Thanks, Chris.  I have an '87 EVTM and will check in a while.

[Gary Lewis]

Give that man a star!  

HOWEVER, there are two issues here:

Having a label that says "Emissions" in the warning lights. Big Blue's left-hand warning indicator says "Emissions" and it has a bulb in it - I just checked.  It comes on when you turn the key to On, and it stays for a few seconds to prove the bulb works.  But, there is no connection to that bulb in any other components in the truck beyond the test function when you turn the key on.  So, this appears to actually be the Extended Useful Life Indicator shown in both the EVTM and the wiring diagrams, although not used in Big Blue.

Having circuitry that is driven by the computer to actually indicate that there is a problem.  And that doesn't show in the EVTM until 1987.

My guess is that Ford knew that the MIL/CEL function was coming, so put an indicator in the dash saying Emissions in 1985.  But, that it was nothing more than the Extended Useful Life gimmick until 1987 when it got connected to the computer.

Here's the page from the 1987 EVTM, and I've circled the Emission Warning Indicator as well as the feed to the EEC:




And here is the same page from the 1986 EVTM.  Note that the light was the Extended Useful Life Indicator.

[myrl883]

Yes, IMS is Inferred Mileage Switch. Ford started those in the early 80s to turn on the Emissions light to remind you to take your truck to the friendly dealer for inspection.
It is NOT connected to the processor, so it does NOT indicate a problem of any sort.

It's called "inferred mileage" because it also has no connection to the odometer. It simply counts how many times the vehicle has been started since the last reset of the switch. Now, what engineer calculated how many times you start your truck in 30,000 miles??

[Gary Lewis]

Do you know when they started the IMS?

[myrl883]

Looks like 1981. Base number is 12B514. The odd part is that I don't see them in the car catalog, so it may be a truck thing, which seems really odd!

[Dyn Blin]

For a random data point:

My '82 that rolled off the CA Milpitas line has no dummy light window for "emissions", nor does it have the bulb (nor wiring), and the owner's manual/guide doesn't mention it.  The shop manuals don't seem to share a reference either.

EDIT:  However, my '82 EVTM *does* show a diagram reflecting an inferred mileage sensor for 5.0 and 5.8 CA-only vehicles.  (Maybe mine being manual transmission meant a delayed implementation per Gary's next note?)

[Gary Lewis]

Yes and no.  I do see 12B514 in calibration parts list #117, but that's for a 1981 w/AOT (AOD) in CA.  The first non-CA usage I see for an F-Series truck is parts list #447, which is for an '85.  Do you agree with that?

[85lebaront2]

Darth had one and it never came on, he also had the IMS there connected to it.

[Gary Lewis]

Mark/Dyn - The calibration parts lists for the 1982 manual transmission trucks in CA don't call for the infernal mileage sensor.

So, what label do you have in the far left window?

[85lebaront2]

Gary, AllData does not have a good set of diagrams for a 1987 truck EFI system but a CEL/MIL is shown on the warning indicators. Maybe Jim can check his 1987 EVTM sometime. 1988 does show it and it is pigtailed off the STO wire from pin # 17 of the EEC which is the same wire you can use a test light or voltmeter to read the codes. So it looks like the CEL/MIL started in 1987, but the emission light was there earlier, but not used for anything except to sell service.

You might be able to rewire it to pin # 17 and the STO wire and use it, I do not know if the 1985.5-1986 EECs will actually illuminate it.

[Dyn Blin]

I see what you did there...

I was surprised to see nothing in that window when I replaced the panel lights and ammeter a few months back- it has a black film installed in the same manner as the other colored warning light films.

Not to drift the thread topic but I see my EVTM also shows a parking brake warning circuit my truck doesn't have...

[Gary Lewis]

Bill - You missed my earlier post with a snippet from the 1987 EVTM - which I also have.  It does show the Emissions light and it is hooked to the EEC, although it says to pin 18, which is circuit 223 and T/LG wire.  But this is for the 5.0L engine as the 4.9L didn't have it yet - according to the EVTM.

[Gary Lewis]

So they had instrument bezels with black plastic and instrument bezels with, presumably, Emissions. And manual transmission trucks got one and autos got the other.

Hard to believe it would be worth the effort. 😳

Did what, bull-rider?  😎

[Ford F834]

Gary, I’ve looked at quite a few bezels, as you may remember, while attempting to document the engineering numbers on them. What I saw was 80-82 had that window blacked out. 83/84 had the upshift indicator there, and 85/86 had emissions.  

I’v also noticed a square light bank in Econoline vans that appears to be the same module as the 83-86 diesel GP/Temp/WIF indicator but with just a single light that says “emissions”. Unfortunately I have not been paying attention to the year on those vans, but I will look next time.

[mp470]

Thanks everybody, didn't expect to start such an in-depth discussion.

[1986F150Six]

<quote author="Gary Lewis">
Mark/Dyn - The calibration parts lists for the 1982 manual transmission trucks in CA don't call for the infernal mileage sensor./quote>

Hmmm? Infernal or inferred??? Freudian slip??

[Gary Lewis]

Jonathan - That's a good summary.  But it begs a question: Was there an indicator in the CA trucks with the inferred mileage system?  I've perused the catalog again and there's no mention of a special instrument bezel for the CA trucks.  None.  So if the window was black, as Mark/Dyn Blin's is, then where was the inferred mileage warning indicator?

I've started a page on the Inferred Mileage System so we can capture what we learn.  And from what I'm seeing shows there wasn't a warning light.

David - Mark said "I see what you've done".