Pontiac firebird check engine light on

[Chad]

Greetings from California! Hi this is my first post on this forum. I am an 18 year old college student studying automotive technology at my local community college. I am studying to become an ase technician and eventually a master technician.

Anyway i just bought a 1984 Pontiac Firebird Trans Am with 68,000 original miles. Car is a 5-speed manual with the Chevy 305 small block. The car turns on the check engine light after about 10 minutes of driving after it gets to operating temperature but the light goes off when the engine is re started and appears only when the car gets to operating temperature. Im not very good with obd 1 so i had a local mechanic look at it and he says its a temperature circuit failure… What does that mean? My friend reccommended i try disconnecting the coolant temperature sensor while the cars running but it still runs 170 degrees with or without the temperature sensor connected. I need to get this fixed immediatly because the car needs to be smogged and if the smog tech sees the check engine light its an automatic fail and im on a budget trying to fix this car.

The car has a electric fan with a manual on/off switch bypassed fan control circuit, new thermostat, new O2 sensor and a exhaust manifold leak. This thing is driving me nuts trying to get the check engine light to go away :angry: All help is greatly appreciated.

Thanks,
Chad-Apprentice Technican

Topic

[Its me]

Gotta set the wayback machine for this one…

First you can pull the codes yourself by using a jumper wire on your DTC and then count the flashes on the check engine light…

Click on this link to read more… http://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

There are probably two temperature sending units on this car. One for the gauge and one for the computer. The computer one is the one you need to inspect…

The electric fan with switch is suspect, as the gauge should tell the computer the proper coolant temperature which in turn, turns on the fan…

My guess is you have an interesting wiring situation going on…

The funny thing is that I can remember seeing these cars (1984 Trans Am’s) on the showroom floor and all shiny and beautiful…. LOL I’m old…

P.S. I keep one of these brand scanners still around for OLD GM’s I have to work on…

http://www.ebay.com/itm/BRAINmaster-3210-GM-scanner-kit-1980-1-2-83-w-case-manual-adapters-/291128806913?hash=item43c8a10e01&item=291128806913&pt=Motors_Automotive_Tools&vxp=mtr

-Karl

[Chad]

Thank you for the help, and for that website. Its gonna either be code 14 or 15 according to my research. I found a stray green wire thats not plugged into anything and it might be the issue but the car runs really well. Ill look into the bypassed electric fan because that makes alot of sense that the car has lots of added stuff from the previous owner, i just wish i had a dad or grandpa or uncle that know more about these old cars cause they are really cool 🙂

[Its me]

What I may recommend is to get a 12 month ALLDATA subscription to this year, make and model of car… (it is around $12.95)…

This will show you the electrical schematics for the car..

I understand how you feel about not having a dad, grandpa or uncle that could help…. I will tell you I learned it on my own without any help from the above…. sometimes you just have to go it alone…. If it is your passion then so be it….

Not to sound like an old fart, but you have it pretty good… (RAMBLE BEGINNING)… There was no internet and the only way you could learn things (back in the day) was either reading a book (like today) or working on the cars over and over and hearing about things passed on by those more senior to you… Now people post how to do it for free YOUTUBE…. The information age has raised the water level for all of us….

I admire you for getting a car this old and working on it… Back when I was your age, I remember looking at a 1967 OLDS for $400 and passing on it because it was shooting flames out of the carburetor..

I learned by getting a piece of crap and fixing it… by trial and error (mostly error).. but nowadays you have a lot of people to help you…

Be specific in your requests for information, take pics and describe the issues as best as possible…

R/

-Karl

[Chad]

Hi Karl i have access to All Data and mitchell on demand for free at the local college i am attending so i for sure will be looking at that because you reminded me of that. I am so thankful for people like you and my college auto instructors going out of there way to help me for free and i will be more specific on my next posts.

Thanks again,
Chad

[EricTheCarGuy]

I honestly don’t have much to add here. I think ToyotaKarl has made a lot of good points.

Keep us posted on how your Mitchell/AllData searches go, and keep us posted on your progress with the problem. You might also find this helpful.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

http://www.ericthecarguy.com/faq/solving-automotive-electrical-problems

[Chad]

Hi eric my friend Checked all the wiring with a test light and all the wiring is good, has brand new coolant temperature sensors so that couldnt be the problem either so we sent out the pcm/ecm to a shop and it tested bad. $200 later a New PCM fixed my car.

[EricTheCarGuy]

Unfortunately GM’s of that vintage did have PCM problems. Honestly, they had a lot of problems. That said, with your new occupation you’ll get plenty of practice and experience. Still a fun car though.

Keep us posted and good luck in school.

[Chad]

Bad news:

As you know Got rid of the check engine light took the car into a local mechanic shop for a smog. Car passed smog test and underhood inspection.

The car burns oil because it needs new valve guides/valve guide seals so the shop failed my smog test because visually the car smokes alot.

I tried to pay the smog tech an extra $20 to pass it but he told me that California has very strict smog rules and the B.A.R. stops by every so often to make sure they are following the rules. Also customers will come back years later and blame the shops for wondering how the car passed smog in prior years and can lose their smog license. The technician told me to get the B.A.R. to do the CAP program which will pay me up to $1500 for the car to take it off the road so i am gonna have to do that because i have no other choice because the car wont pass smog. If i knew of some shady shops that would pass smog for an extra fee i would be willing to go that route.

[Bill]

Well that sucks…Buy yourself a bottle of Lucas oil stabilizer and pour the whole bottle in to see if it stops smoking long enough to get it through emissions.

[Author]

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