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]

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.

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

[Gary Lewis]

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

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

[Gary Lewis]

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

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]

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.

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]

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??

Do you know when they started the IMS?

[myrl883]

Do you know when they started the IMS?

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]

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!

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]

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!

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?