"Check Engine" light blues

[HammerDown]

Hey Mike>>>

So I did as you suggested...jumped the far right (A) and the next one over to the left (B) with a paper clip....turned the key to run...waited.....and waited...and waited for the "check engine" light to blink...and waited some more. It just staired at me...no blinky!
Uh...OK...now what?
If it did blink, you said it will repeat code 12, 3 times and go onto the next code 44 or 45?
But you never told me how to recognize how those codes blink?...thats if it did blink!
Thanks for your feedback...Ray

 

[HammerDown]

Post Bump....

 

[Stingray6974]

Hi Ray,
Something is not right here. The two terminals side by side in the ALDL with a slot cut in the wall seperating them are the ones to be jumped. Because of the slot you can use a wide male terminal end to contact the two terminals at the same time. With the terminals jumped and the key turned on the check engine will start to flash immediately. Sounds like you might not have been making good contact.

Mike

 

[HammerDown]

Hey Mike>>>

Best as I can explane it...as I look down onto the ALDL connector, there are 5 spades, with (3) divider walls towards the right> side, the 2 on the far left dont have a divider...the rest do. I checked with a small mirror to make sure the farthest right and the next one over to the left did infact read B+A as ya look down at them...those were the 2 I jumped.
I'm pretty sure I made a good contact as I tryed it several times...could the computer be loosing the stored codes?
Do I have to test it right after the check engine light comes on?

I'll try again tomorrow...thanks again for all your time...Ray.

 

[bradfordsvettes]

sounds like a possible tps problem or o2 sensor but you need the flash codes like mike said a scan tool would be very helpful steve

 

[Stingray6974]

Ray,
If it won't flash code 12 it's not going into self-diagnostics. I would take the car to someone with a scan tool and have them see if it will pull codes before you do anything else. It might take some looking since the five pin ALDL was only used on 1981 Gm cars and 1980 California corvettes.

Mike

 

[HammerDown]

Thanks for all the suggestions and help...I hope to take the car to my friends shop and see whats up.$$$$$$$

 

[UKPaul]

Best as I can explane it...as I look down onto the ALDL connector, there are 5 spades, with (3) divider walls towards the right> side, the 2 on the far left dont have a divider...the rest do. I checked with a small mirror to make sure the farthest right and the next one over to the left did infact read B+A as ya look down at them...those were the 2 I jumped.

Ah! You jumped the two terminals on the right that had a divider between them? It's the 2 on the left without the divider that you need to jump. It seems that some cars had these ALDL connectors fitted in the opposite direction to others. Mine is fitted in the opposite direction to what the manual says, so I initially jumped the wrong pair. Don't worry, it shouldn't do any damage.
Try jumping the 2 on the left & see what, if any, error codes are displayed (apart from 12).
It could very well be a mixture problem, but the 1st thing I thought when I read your post was that maybe the O2 sensor was cooling down after a period of idling & then giving erroneous readings?
These computer systems are pretty simple really, they just seem complex when you first start looking at them
Good luck

 

[HammerDown]

Ah! You jumped the two terminals on the right that had a divider between them? It's the 2 on the left without the divider that you need to jump. It seems that some cars had these ALDL connectors fitted in the opposite direction to others. Mine is fitted in the opposite direction to what the manual says, so I initially jumped the wrong pair. Don't worry, it shouldn't do any damage.
Try jumping the 2 on the left & see what, if any, error codes are displayed (apart from 12).
It could very well be a mixture problem, but the 1st thing I thought when I read your post was that maybe the O2 sensor was cooling down after a period of idling & then giving erroneous readings?
These computer systems are pretty simple really, they just seem complex when you first start looking at them
Good luck

Ah, but regardless if the divider or even if it was installed from the factory in reverse...are the terminals to be jumped A+B ? There the ones I jumped.

 

[vettenick]

Try to get your hands on a scanner to see what code(s) are being set. If you can't get a scanner, I can walk you through the manual mode of getting codes. The only drawback to that is that you won't be able to view live data . Your oxygen sensor could be going bad. After long idle periods it could be dropping out and not giving the computer any or no input. Just a thought.

 

[UKPaul]

Ah, yes but... I've got one manual that says pins A & B should be jumped & another that says pins D & E!! Just ignore the labels & jump the two pins without the divider (if you look closely there should be a divider with a slot cut in it). I spent a while trying to follow the manual regarding what pins to jump & got no codes. When I jumped the pins without the divider I got the codes flashing
Hope it works!
Paul

 

[HammerDown]

Sounds like a plan..I havent had much time to mess with the Vette..(working on winterizing the boats)....but I'll get back on this "check engine light".
Thanks for the new suggestions fellas...:cool

 

[HammerDown]

Check Engine Light Gave me Codes

Not that I know what they mean...but when I jumped the 2 terminals without the divider (thanks UKPaul), it started to blink...and this was it.

*/*** Repeated I belive it was 3 times

**/*** Repeted 3 times

**** Repeted I belibe it was 6 times.

Then started all over again.

OK, so now what?

Thanks for the advice...Ray

 

[HammerDown]

Nothing yet...guys:confused

 

[Yoda]

Re: Check Engine Light Gave me Codes

Not that I know what they mean...but when I jumped the 2 terminals without the divider (thanks UKPaul), it started to blink...and this was it.

*/*** Repeated I belive it was 3 times

**/*** Repeted 3 times

**** Repeted I belibe it was 6 times.

Then started all over again.

OK, so now what?

Thanks for the advice...Ray

Hammer,
Could the first message (flash) possibly be *~**? If memory serves me correctly the computer should flash code 12, which is a self diagnostic test prior to flashing trouble codes, it should then flash the trouble codes and go back to the code 12 then start the process all over ..

• *~*** in my mind would be a code 13 (oxygen sensor) this code usually will clear after the engine is warmed up and at operating temp.
• **~*** again my analysis would be code 23 (Open or grounded M/C soleniod circuit)
• **** not sure here, could be a code 44 (lean oxygen sensor indication) here again this should clear once the engine is at operating temp.

Good luck, I will copy this thread into the L81VetteRegistry Forums here at CAC for possible help and future reference..

 

[Hib Halverson]

If you get: flash (delay) flash, flash, flash with the sequence repeated three times, that's DTC13.

If you get: flash, flash (delay) flash, flash, flash with the sequence repeated three times, that's DTC23

four flashes repeated six times is probably a mistake in reading the light, or, as suggested above, it's a thrice repetition of DTC44, ie: flash, flash, flash, flash (delay) flash, flash, flash, flash.

What I'd do before you start throwing parts at the car is clear codes and road test. Also, with an 81, because the O2S is so far back in the exhuast system and the ECM's clock speed is so slow (can be benchmarked with a sundial), a road test means not only round town but some expressway driving. If the light comes on again and the same codes are set, then I'd get the factory service manual and troubleshoot each DTC according to the instructions in the book.

Keep in mind that because of the ECM's slow clock speed, sometimes diagnosing the 81 system can be challenging becuase problems which, today would set hard codes, were often missed by the engine controls diagnostics and, thus, acted like intermittants. Such was life back in the stone age of OBDs but, back in 1981, that was absolutely leading-edge stuff and GM has a huge technology lead on the other OE's with it.

 

[HammerDown]

Thanks for the replys...(Hib) your talking in Greek to me, wish I understood just what your saying.
I jumped it again...it flashed the same as I stated above. However I will clear the codes, (this is done by disconection the Batt for about 20 mim...correct?) and then I'll run the car and check the flash again.
I would like to fix this myself as I do all my own work...but computer stuff has me scratching my head...But I'll rebuild a BBC 572 every way from Sunday!
Thanks again for all the suggestions...Ray.

 

[UKPaul]

Ray,
I'll try to decode a bit of what Hib said. DTC13, DTC23 are Diagnostic Test Codes 13 & 23. ie what the flashing light is telling you.
When I've had test codes flash up they've always been preceeded by the light flashing code 12 (DTC12) 3 times. Then the (2 digit) error code(s), followed by 12 again to show that all codes have been displayed. The cycle is then repeated for as long as you short the terminals.

I'd check the codes once more (take a note of them) & then clear them by disconnecting the battery for a while. And, as you'll be groping around in the storage compartments, remove the tray in the p.side compartment & you'll be able to see the side of the computer just in front of the battery. There'll be 2 connectors on the computer & it'd be worth pulling each of them off & then sliding them back on to clean up the contacts (while the battery is disconnected). Mine was playing up when I 1st bought it & fiddling with those connectors solved a lot of the problems (probably a dirty/bad contact).
Then conect up the battery, give it a road test & see what error codes are displayed.
The computer (ECM or ECU) runs very slowly compared to modern stuff (a slow clock speed). Consequently it can "miss" an intermittant fault & not store it as an error code (error codes are what's flashing at you when you short those 2 pins together). What he means by "challenging" is "a real PITA"!! As you've got error codes stored in the computer then yours should be plain sailing to fix.
Computers in cars can be a very difficult thing to diagnose without expensive test kit, but the one in the '81 is very basic so it's not to difficult to work out. Additionally, the fact that it can store diagnostic test codes makes fault finding very easy at times.
Good luck

 

[HammerDown]

UKPaul...thanks for brakeing it down for me...in a day or so I'll get back on it. I'll also disconnect/reconnect the connectors at the computer and then road test, check codes again.
Thanks everyone for being so patient about this...Ray

 

[HammerDown]

Update... will I disconected the Battery for about an hour...also removed the 2 plugs from the computer. Drove it around and so far no check engine light.
If it happens to come on I'll jump the terminals again and see how it flashes.
thanks...Ray