Can appreciate that I'm new to this site, and I searched, and found this specific link. Spent a fair amount of time under the dash....searching all over the place under the driver/steering wheel area, and did not find the ALDL. Went and bought a Chilton (which I swore I'd never buy another Chilton/Haynes manual), but there it was....Evidently I don't have a ALDL because evidently in 1980/305/CA it was the predicessor to the ALDL discussed in link above. Looks like I have a "C-4" as opposed to a CCC system, so this link when stated "I think it was first introduced in CA. in 80..." appears to be incorrect. No harm...no foul. I just have to figure out how to deal with a "diagnostic lead". I ground it per the Chilton, but now I'm confronted with a new delimma...I don't have any SES light. In typical Chilton style, it really doesn't go into where to go as far as trouble-shooting from this point with the C-4 system. Anyone have an '80/305 that can verify there is a SES light. I'm guessing it would be in the row of status lights to the right of the gauge cluster...where the CHOKE light is, but I'm guessing.
Thanks in advance.....

 

HANES MANUAL 24020 page 6-5 obtaining trouble codes. (a) On 1980 models, locate the single wire green connector taped to the wiring harness near the ECM, the ECM is located under the dash, on the passengers side, behind the glove box. with the engine running, connect the terminal in this connector to a good chassis ground. When the diagnostic terminal is grounded with the key on , engine off, the ECM will display a "code 12" by flashing the check engine light. A code 12 is simply one flash, followed by a brief pause, then two flashes in quick succession. This indicates the system is operating properly and capable of trouble code output.. The secret has been revealed.. hope this helps.
Ted Dubree:let_it_all_out:

 

K....pick on the new guy....But again..why I'm not a big fan of HANES/Chiltons....Please read and analyse..."with the engine running, connect the terminal in this connector to a good chassis ground. When the diagnostic terminal is grounded with the key on , engine off, the ECM will display a "code 12" by flashing the check engine light. A code 12 is simply one flash, followed by a brief"..WITH ENGINE RUNNING...ENGINE OFF...???? I understand the whole idea of the one flash/2 flash, and I understand grounding the diagnostic terminal. I did this and I had no light of any sort flashing. That is why I asked if someone could confirm in a '80 CA 305 might be. What I've been able to figure out is that the C4 system, unlike the CCC system has no retentitve memory. ie: every time the key is turned off, any code clears...So simple logic would be why would there be a SES/check engine light, regardless of what Chiltons/Haynes prints. Evidently you can jumper the orange wire on the ECM to the battery and it will retain a code, but again this is what the Chilton's manual sez, but something about running 12 volts into the ECM, I'd rather have someone with practical knowlege confirm that makes sense. I know I had a good ground and I could hear what I assume is the solenoid in the carb cycling...just no light...Not trying to rub anyone the wrong way, and I'll freely admit I'm the stupid one here. I have an '80 CA 305 Corvette WITH the CCC /SES light so I thought I knew what I was getting into. Talk about stupid dripping from me...now I've got 2 '80 urchins. Not a fan of the General at this point....:???:

 

Great Info!!! I'll take the instrument cluster out. I took a real close look at the lights/lenses and there is one that appears to have been painted over from the outside...My guess at this point is that was the solution someone came up with to "solve" the SES light being on. If this is the "missing link" (pun intended) and there is a bulb, and the bulb is good do I assume the ECM is bad and just replace? Are the GM C4 manuals you refer to still in print and available? How much of a challange is it going to be to find the correct ECM if I need to go that route? I'm guessing only refurbished units are available, and I bet this is something I don't want to even try to source thru the chain auto parts stores. Ernie...again many thanks....

 

Short/sad tale. I had a nice '79 that I was accumulating parts to take it to the next level. Some dirt-bag ended up stealing it. I found this '80 and it was rough, but it was a starting point. Living in CA. I have to get it smogged, and for the most part, I want to play by the rules with the smog police. As I said earlier, I have an '80 Vette, and I got that to pass smog, but that one has a CCC system. Symptoms on the ELKY is it runs good, but every once in a while it will puff smoke. At first I thought valve guides, but you can smell the unburnt gas when it does this. Plus it cleans up with bring the RPM's up. I replaced the air cleaner and could smell the raw gas when I did this. Pulled a plug and it definately is rich. All smog equipment is there. First thing I'm going to do this weekend is pull the dash to see if there is a light bulb behind the SES light and scrape the paint off that someone along the way painted over the SES lense. I found the grounding terminal, did let the car run for over 5 minutes, ground the terminal while the engine was running, but no SES light-up. The ECM must be doing something because I shut the key off and I could hear the carb solenoid cycling when the terminal was gorunded.
Again, many thanks...

 

Got the dash pulled and sure enough someone had paint over the CHECK ENGINE light lense. The bulb was also busted off in the slide-socket. I got the broken bulb out and used the CHOKE bulb which I know to be good. Turned the key and still no light. Started it up and ran it for 10+ minutes and ground the diagnostic lead with the Elky running...nothin'. ECM time or?

 

Ernie...you're my hero!!!:nanawrench:I got 2 of the manuals you listed off of E-Bay, so this week-end I'll figure out what is up. I'll start a new thread and detail my findings so if someone else in the future has a C4 system issue it might be helpful. Could I ask 1 more favor of you? The manuals I got are great. As I stated previously I have an '80 Corvette that I blindly got to pass smog, but if I had the ALDL version of these manuals I'm sure I could have gotten it to pass easier/cheaper then what it took. Do you have the number(s) for the manuals that would cover the ALDL systems?
Thx. in advance,
:You_Rock: