pdf17

Yes, have done a search and yes, have reached out to Porsche Cars North America -

Did this year have a functional CEL? Hopefully Porsche Cars NA will come through so that I can get my smog test certificate in SoCal. Emissions readings passed easily but, the tech looked for a CEL and said that it wasn't lighting.
The owner's manual makes no reference to it but, there is a space and image on the dial for oil pressure and temp. This is stated in post #7 of this thread (see, I did do a search hehehe)
https://rennlist.com/forums/964-foru...3-ca-smog.html

I was hoping that somebody may have something definitive, maybe in writing, from Porsche...

Thanks!

David A

Get it to TLG, they will get it to pass, mine passed 1st shot.

http://www.tlgauto.com

Talk to Marco.

C24FUN

I had to check my manual to see if you were right! Sure enough there isn't any mention of a Check Engine light in the 1990 C2 manual. The reason this surprised me is that I have had a functioning Check Engine light in my car for so long I couldn't figure out why the manual wouldn't mention it.

Then I remembered that I had swapped out my DME chip way back around 2003 with a one that came with the Autothority MAF I installed. I think they used the California mandated version of the chip as the starting point for the product so the Check Engine light has functioned in my C2 since then. I looked at my records/notes for this and can say with some certainty that the "non-California" chip part number is 126 735 6142 (came in the 911 618 124 -01 DME up to 1990) , and the "California" chip is 126 735 7006 (from the 964 618 124-03 DME, 1991+) which has the CEL and Fault Code readout function. I still have copies of each of these chips in my parts bin.

So if you swap out your DME EPROM for the California version you will be have a working CEL and be able to read out all of your fault codes.

Good luck!

Jim G.

pdf17

David and Jim,
Thank you both very much. I gave the info from Jim's post to Marco at TLG and he said he's never experienced it but, willing to check it out.

Thanks again!

pdf17

So here's what TLG (Tony and Marco) and I determined -
1. Factory plug behind the mylar imprint for CEL so my year was not intended to have a light.
2. Light works and functions properly if the plug is replaced with a bulb.

RicardoD

I am running into this headache with CA Smog on my 1990 C4. Clueless shops think the CEL should illuminate based upon "their system" but the CEL was fully activated starting in 1991 USA models. So people think I am trying to cheat the system with an unpopulated bulb. I remember fighting this in the past by pulling out my 1990 Owner's Manual showing zero reference to this light. But if you shine flashlight at the gauges you can see where Porsche eventually turned it on. I am going to try populating it so I don't have to deal with this anymore.

Ralph3.

Pretty sure my 1990 C2 cab has a functional check engine light. It’s originally a California car.

Hatzenbach

Could someone with a working CEL please let me know how it announces itself?
Does it come on when you start the engine and then goes off or how does it work?

Ralph3.

Comes on when ignition key is turned on to position 2, goes off when engine starts position 3.

RicardoD

I passed my 2021 California SMOG test on my 1990 C4!

Here is the summary;

The Check Engine Light (CEL) was implemented in the USA starting in the 1991 model year. See Adrian's book where he documents year by year changes. In addition a check of the factory wiring manuals show that for the 1990 USA model year that bulb is NOT used. I you look at the 1991 wiring diagram the build IS used. It is not simply populating the light but a DME program update that also activated it. I think it just checks for O2 sensor function. You can't just put a bulb into your 1990 CEL position and get it to work (one local 964 owner to me tried this and it didn't work). Now this same owner figured out a simple way to get the CEL to turn ON with ignition and then turn off when the car starts (perhaps he can post here).

More importantly this change from 1990 to 1991 is documented in the reference book used by my local SMOG place down the street from Canepa (thanks Dusty for the reference). The reference book they use entitled (Emission Control System Application 2020 Edition) notes a change from 1990 to 1991. In this book both 1990 and 1991 say YES to Computerized Engine Management with 1990 having the 29 footnote, and 1991 having the 6 footnote. 29 = Digital Motor Electronics and 6 = Digital Motor Electronics Equipped w/MIL So you can see that the malfunction indicator lamp (MIL) starts in the 1991 model year and noted every year after.

Thankfully before the test was started I explained my issues smogging the car, the CEL change from 1990 to 1991, and the tech recalled looking at these footnotes in the past. I didn't have to show him my owner's manual or Adrian's book. We looked at the book together and that was enough for him to proceed. I don't know what reference system the other shops I had trouble with used.







Larry's Auto Care SV
5346 Scotts Valley Dr
cotts Valley, CA 95066

Ralph3.

Ricardo interesting stuff, was your car originally a California car C03 country code?

I looked in my owners manual and there was no mention of a check engine light but I seem to have one.

RicardoD

My car was originally a Portland, Oregon car

Hatzenbach

here you go: https://rennlist.com/forums/964-foru...l#post17792394

C24FUN

Another way to get your early, non-CEL vehicle through the test is to just swap out the ECU chip to the California Smog accepted version.

Removing the ECU from under the drivers seat, opening it up and replacing the EEPRPOM is not really any more challenging than the procedure referenced above and has the advantage of not requiring any plug disassembly or soldering as well as giving you the fault code display. It does require 2 steps:
1. Removing your oil gauge and installing a bulb in the Check Engine position.
2. Removing your ECU from your Porsche and carefully opening it up on a workbench to replace the original EEPROM. An excellent step-by-step procedure for this has kindly been posted by Jason Andreas here .

Oh, and you also have to get yourself a copy of the correct EEPROM. The standard North American PROM part number was stamped 1267356142 (this is what came in my Canada delivered car) and is listed as 964.618.124-01. The California part was stamped 1267357006 and was listed a 964.618.124-03. This is the one with the CEL functionality in it and it is a drop-in replacement for the original.


The 3 EEPROMS I have for my 1990 C2.

If anyone wants to follow up on this I have the binary file for the CEL compatible EEPROM. These 32K EEPROMs (27C256 or equivalent) are still readily available. A PROM Programmer is also required along with the .BIN file to generate a factory equivalent chip. Even if you don't have the tools to program the EEPROM, you may have an electronics hobbyist for a buddy or know of a local electronics shop that might do it for you. Once you have swapped the chip and replaced the ECU you will be able to display any fault codes by using the technique generously documented by Bill Wagner here.

I hesitate to attach any info that may be Porsche proprietary on the forum, but if you want to contact me via PM I can provide the binary file for the CEL compatible code.

Cheers,

Jim

DIS

Hi

I have a 1991 C2 Tiptronic which has the Check Engine light. The trouble I have it that the light come on at time and then it goes off.
I can and have checked for codes, but no code appears.
If I am lucky when getting smog checked, the light may not come on, or the technician does not notice it.
So the question is: Why does the light, and sometime both lights - the big exclamation point, come on for a minute and the turn off?
Car is a CA car, bought in CA new, and still in CA.
THanks
Don S.