Check engine light on, but no codes stored

[djsroknrol]

Now that the car is back on the road again, I've had a chance to get to a few minor things, but this is a puzzler...the check engine light is on constantly. I tried to pull the codes, and got a code 12 with the terminals jumped, but there aren't any stored....what a time I had finding the ASDL connector; it was hidden under the I/P kick panel on the drivers side...not mounted like I've seen in other rides.

The FSM isn't very helpful in this department and wondered if anyone else had had a similar problem and how did you go about solving it?

 

[Schrade]

I think 12 means communication with the ECM from the ALDL interface - normal (did it flash 3 times?).

I wouldn't trust any 'readings' too much until the rebuild... Any progress there?

 

[djsroknrol]

I think 12 means communication with the ECM from the ALDL interface - normal (did it flash 3 times?).

I wouldn't trust any 'readings' too much until the rebuild... Any progress there?

It flashed 3X code 12 and then just flashed code 12 after that.

As far as the engine rebuild goes, it's in litigation now...got a high profile lawyer on the case now. My son and I dropped the pan, pulled a HANDFUL of RTV from the pickup tube and screen, installed as new oil pump, ran an engine flush with a new filter and refilled it with a second filter....she's got 30lbs@1500RPM and 10lbs at idle. I figured it was good enough to drive while I'm waiting on the outcome and the best thing is...I still don't hear a knock (fingers crossed)

 

[Mac]

Thread split at request of originator.

-Mac

 

[djsroknrol]

bump...back on topic;

The FSM doesn't show a SES light troubleshooting flowchart on this...anyone have any ideas or knowledge on this?

 

[Schrade]

FSM has EVERYthing - promise. It takes a LOT of reading, a LOT of bookmarks and fingers (better pull a shoe too, and get 5 handy too).

Getting familiar with FSM is not gonna' happen overnight. But it IS in there.

Check the beginning of section 8D (that's a stab in the dark, and if I'm wrong, $5 says you-know-who will tell me I'm wrong). And of course, they won't tell where it is... otfl

 

[boomdriver]

FSM has EVERYthing - promise. It takes a LOT of reading, a LOT of bookmarks and fingers (better pull a shoe too, and get 5 View attachment 1888 handy too).

Getting familiar with FSM is not gonna' happen overnight. But it IS in there.

Check the beginning of section 8D (that's a stab in the dark, and if I'm wrong, $5 says you-know-who will tell me I'm wrong). And of course, they won't tell where it is... otfl

Agreed... the info IS in there somewhere. Often not in the obvious section, but hidden away in a related section of the book on the back of a page. The ONLY book more detailed than the Corvette FSM is the assembly guide for the space shuttle...

Seems like that symptom would indicate a bad prom or ECM...if its showing a code 12 in the correct series of 3, then 3 again to show the end of the memory display, that says operation is normal with no trouble reported, but stuck in open loop. That can happen if the calpak or prom is bad. Check the prom for bent pins and the plugs for wires pulled out.

Next wild guess would be what happened inside the exhaust? plugged cats, mufflers from trash going thru there? excessive back pressure that the ECM has no code for?

 

[gmjunkie]

Now that the car is back on the road again, I've had a chance to get to a few minor things, but this is a puzzler...the check engine light is on constantly. I tried to pull the codes, and got a code 12 with the terminals jumped, but there aren't any stored....what a time I had finding the ASDL connector; it was hidden under the I/P kick panel on the drivers side...not mounted like I've seen in other rides.

The FSM isn't very helpful in this department and wondered if anyone else had had a similar problem and how did you go about solving it?

CLEAN and INSPECT EVERY GROUND CONNECTION ON THAT VEHICLE!!

High Resistance or Non-Existent GROUNDS make Electronics Do Weird SH*T!~!!


PS If you had the engine out,you may still have one or more dangling behind the engine!!

 

[djsroknrol]

Solved....missing low coolant sensor on radiator.

Funny, no mention of a 3rd sensor in the FSM......