Question: constant blinking on check engine light

[PokerJoker]

Phwo this is a difficult one.

First the clicking mc solenoid sound is only hear-able when you want to read the codes NOT when you want to start the engine!
Are you sure the other ECM is a good one as the light stays on and you can not pull any codes?

With the ECM light on the ECM will stay in open loop so there should be no to little difference with a broken ECM I think.

Greetings Peter

Thanks Peter,
I've always been able to hear the "clicking" from the carburator with the key in the switch and the switch on, just before cranking the engine. Was that not normal?

I"m not sure if this new ECM is good or not, it was used and one a friend just let me try to see if anything changed. I will purchase a new rebuilt ECM if you guys think that is the next thing I should try.

UPDATE:
So, I pulled out my old OTC Monitor 2000 and hooked it up to see if I could get any trouble codes with it. As fate would have it, I did get three trouble codes...oh happy day!

Code 54, code 23 and code 41...now 54 and 23 are related to the M/C solenoid, but I can't find anything about a code 41in my shop manual, but those are the three numbers that kept flashing. In the OTC book it says...
Code 23 - M/C Circuit Solenoid Low
Code 54 - Shorted M/C Solenoid or Faulty ECM
Code 41 - There are two things listed for code 41, but neither apply to the 1981 model...one was No Distributor Ref. Signal and the other was Cam Sensor Failed...but in the chart the mode years listed are 1981 through 1984 and there are no "x" in the boxes in the 1981 column. So that makes me think this code would not apply to my car.

 

[RC81]

I think before anything else you need to put in a rebuilt ECM from an auto parts store - remember to change the prom from the old into the new. Also remember the direction the prom is in, so it can go into the new one the same way - if its reversed you will get a solid check engine light.

 

[Wajulia]

The carb should not be clicking when you turn on the key. It will click when you try to read the codes.

I need to jump the two pins closest to the driver side (left side) (on my connector, there are two pins that have a slot between them)

There is no 41 code on a 81 vette.

All codes should clear after power is removed. you should be able to remove power, read codes and only get 12's. That would at least get us to a known position.


So where are we now -- you could have put another bad ECM in OR There is some reason the ECM cannot operate correctly. The connectors need to be clean and it should be getting good power and ground. That is all it should need to operate and give us reliable codes. Do you have a pinout of the connector so you can check power and grounds? I am sure I can get you one if necessary.

 

[PokerJoker]

I'll try to jump the two on the left (drivers side) and see if I get codes. I'll clear the codes first. I should have a digram of the connectors I'll look for it tonight and try cleaning them.

So, no clicking from the carb when the key in and just before starting is normal. That's good, because that is what I have now. I've always heard the "clicking" from the carb before starting...but not since I changed the ECM.

 

[Wajulia]

First -- Of course the check engine light can come on continuously -- if the error that causes the warning is continuous. If the error is intermittent, the light will be intermittent, but the code will be saved. Sorry if I mislead you.


Clicking in the Carb -- You can hear it when you short the test terminals, and if you listen closely you can hear it (not consistently) when it is idling in closed loop, but you do not hear it when the car is on, not started. That was a sign that your ECM was doing some strange things.

I attached a picture of the test terminal. You need to jumper the two pins that have the slot between them (see picture) no matter what side it is on . The picture leads you to believe it is on the right, but in my car it is definitely on the left.

I also included the first sheet ofthe ECM troubleshooting procedure -- it basically tells you to read the codes.

Last I included a picture of the ECM terminal pinouts. I am pretty sure that there should be 12V on Pin R "Continuous Bat" and check the continuity on pin A and U (grounds)to ground. I am also pretty sure that the 5V reference and the 8V supply are sourced from the ECM and will not be present if the computer is unplugged, but you can check to see.

Good luck -- dont give up.

 

[Wajulia]

If you clear the codes, get the 12's and you still get the codes 23 and 54, I put the troubleshooting guides below. They both are pointing to the M/C Solenoid. You can still buy the solenoid and it can be replaced with the carb still on the car, but you will need to take the top off the carb.

 

[PokerJoker]

Wajulia...you are a genius!

Okay, I looked for the test terminals and you are right, mine are on the left side as well. So when I jumped them, I got a code 12 (flashed three times) then then a code 51 (flashed three times) then it repeats. So I see the chart says to check the prom and make sure it it seated correctly for code 51. I'll do this tonight and check it again.

No, code 23 or 54 this time, but I did clear the codes before I checked it, so I may need to actually start the car for these codes to reappear...but I am making progress (I think)

Thanks for your help.

Jeff

 

[Peer81]

Before you buy a new solenoid. Check if the old one is still working. I don't think there is a grey space, just it works or it doesn't. Take a 9v battery, put a low weight little screwdriver down the carb vent holes (you can feel it is on the spring loaded solenoid thing..). When you connect the battery to the solenoid for a second the solenoid will charge and it will push (jump) the screwdriver up. If the screwdriver will stay in place then you need a new solenoid, if the screwdriver will go up when the solenoid is connected then it's still oke.

Greetings Peter

 

[Wajulia]

Great -- always nice to when things start working as expected. Be careful of the PROM. Make sure it is not in backwards. The Pins can bend under or out when you insert the prom and it is hard to see it after you insert it. Also -- be VERY careful if there is a bent pin, you might be able to straighten it out very carefully, but only once before it breaks off. straighten any pin very carefully with a set of needle nose pliers -- be gentle. If the pin breaks you are out of luck and the only place I know to get another is hyperchip and they are expensive. Do you have the one from your first ECM you can try?

I also agree with Peer 81 -- the solenoid either works or it doesn't work (and most of the time it works) A 9 volt battery across the terminals will tell you. If it moves full throw then it works. If the solenoid codes come back I would check to see if someone bubba'd up the wiring first (like the choke thing). Did you ever sort that out?

Keep going, you are getting there.

 

[PokerJoker]

GREAT NEWS!!!!

Pulled the computer and took out the prom chip. I had indeed bent a couple of pins...carefully straightened them out and re-seated the chip. Wow, those pins are really hard to see while seating the prom. Anyway, they dropped into the slots and it felt right so I very carefully pressed it into place. Reinstalled the computer and jumped the terminals to see what codes would show up.

Got the 12 code and then....drum roll please...the 12 code again repeated, no other codes!!!

So I fired her back up and guess what? NO CHECK ENGINE LIGHT! First time in 3 years (since I've owned the car). Hopefully I'll get a chance tomorrow to take her out for a drive and see if I can notice any difference.

If I still lack power and have hesitation, it might be carb adjustment or fine tuning the timing. But now, I feel like the ECM is doing what it's suppose to. Many thanks to you Wajulia and Peer 1...you guys were very helpful.

P.S. --have not tracked down the choke wire yet. It's still tied into the distributor, the choke light is not on, will it be a problem to just leave it as it is? One other question. I don't have the air pump or catylatic converter on this car, will that be a problem for me?

 

[geekinavette]

I don't know about '81 specifically...but a lot of the earlier GM ECMs flash the CEL rapidly like that when there is a problem reading the EPROM. Bad EPROM, bad socket connection...etc.

Ah-h-h-h-em!

Hahah just kiddin! I KNOW that tremendous "sigh of relief" ALL too well! Its a great feeling ain't it! Glad you got 'er figured out.

 

[PokerJoker]

Ah-h-h-h-em!

Hahah just kiddin! I KNOW that tremendous "sigh of relief" ALL too well! Its a great feeling ain't it! Glad you got 'er figured out.

Haha, yes! Thank you too geekinavette! This forum is really an incredible resource, especially for novices like myself. And yes, "sigh of relief" and I was doing the happy dance in my garage as well!

 

[Wajulia]

FANTASTIC!!!! -- Glad things are starting to get sorted.

Don't be dissapointed if the check engine light goes on -- the codes will now lead you to the issue, and most are easily sorted out.

Now for the original issue -- lack of power and hesitation -- Check the timing, connector on the distributor unplugged, 6 deg. Hesitation is usually accelerator pump -- if it is the original, the alcohol in the newer gas has been known to mess them up. Newer ones are made to withstand the alcohol.

As for the choke -- it is up to you -- I like my car to work the way the factory intended it to.

As for the air pump and cat -- The car will run fine without them both.