I need clarification on this!

CEL check sequence. Ingnition on, engine stopped back probe white ECM connector pin 20 CKT 419 to ground. If test light comes on check for faulty CEL bulb. Bulb OK. When I take 419 directly to ground the CEL Light comes on. That's a good thing! If bulb is ok, repair open Ign. 1 CKT, or CKT 419. If CKT 419 was bad it would not light up the CEL when I put it to ground. Would it?

Next check:
Ign. 1 CKT, I'm assuming that this is the ignition switch because I can not find it anywhere else. It's possibly on the schematic page 1 or 2, but those 2 pages are missing on the reprint for my shop manual. I have ordered a complete schematic that is on a solid page, but it has not arrived yet. What is this suggesting? I would think that this would be the pink wire coming from the ignition switch. Any suggestions on trouble shoot this any further?

Help!

 

Help!

 

I have something different.

Ignition off. Disconnect white ECM connector. Turn ignition on. If the the light goes on repair short in CKT 419.

Light stays off. Turn igntion off reconnect ecm.Ignition on back probe ecm connector pin 3 ckt 451 with test light to ground. Code 12 repair open in ckt 451. No code 12 turn ignition off again. Remove prom. Igntion on. Ground diagnostic terminal(under the ashtray). Note code. code 51 check for proper prom installation or no code replace ECM. If okay (code 51) install new prom and recheck for code 12. No code replace ECM. If you get 12 you fixed it by positioning the prom correctly.

Sounds like you have a dirty ecm or a bad connection under the consol. Follow CKT 419, look for breaks...should also be a male/female connection somewhere.

Good diagram i posted on the other thread. Go to page four. Look for ckt 419 and follow the wire.

Pin 3 on 451 is a ground...same connector up to the left of 419 in the diagram.

http://forums.corvetteforum.com/show....php?t=1863320

 

I see IGN 1 in mine. 419 goes to the check engine light then to 10 amp fuse on the other side then to IGN 1. Have you checked the fuses? Learn something new everyday. I never noticed there was a 10 amp fuse labled ECM in the fuse panel.



As for your question. shows a pink/black strip coming from the ECM indicator light and going to "gage fuses". So brown/white in and pink/black out...
Jim

 

I have checked all of the fuses. I even changed them all with new ones to make sure there was not a problem. When I disconnect the white connector and ground 419 the CEL light comes on. That confirms that CRK 419 should be ok. ( Not open or shorted ) Earlier today I cleaned all of the connections on the ECM with contact cleaner & an eraser head just to make sure. I also have check all of the wires to the ALDL connector. Is there supposed to be some kind of white web type of material over the prom?

I will go out and try your other suggestions to see if they might work.

 

Pin3 Ckt 451 is not a ground. I'm confused. Back probe pin 3 CKT 451 to ground & still no CEL. However if I take my test light to the ALDL connector CKT 451, You can here my throttle bodies kick in & out.

 

Removed Prom and grounded CKT 451 still no CEL light. Are there any other test? When I did this again you could hear my throttle body injectors kicking in. Is this normal?

 

I called it a ground because its a black wire. to late to check now. I'll look into it tomorrow.

Jim

 

did you try all of this?
Light stays off. Turn igntion off reconnect ecm.Ignition on back probe ecm connector pin 3 ckt 451 with test light to ground. Code 12 repair open in ckt 451. No code 12 turn ignition off again. Remove prom. Igntion on. Ground diagnostic terminal(under the ashtray). Note code. code 51 check for proper prom installation or no code replace ECM. If okay (code 51) install new prom and recheck for code 12. No code replace ECM. If you get 12 you fixed it by positioning the prom correctly.

When I say ground diagnostic terminal. I mean get a piece of wire or paper clip bend it into a "U" shape. Jam it into the two pins to the driverside of the diagnostic terminal. So pull the prom, turn the ignition 'on" then ground with the "U" shaped paper clip, remember its the two slots to the left (towards the lighter) The light should flash 12 three times the 51 then 12 three times. The first 12 says diagnostic commencing the middle is the codes and you may get more then just 51. The last 12 says the test is over.

So....you'll get flash....pause...flash flash. One flash for "1" two flashes for 2 then pause and the 12 starts agai. After the third time you will get 5 flashes pause then 1 falsh equals 51.

If you don't get a 51 or anything for that matter. Put the prom back in and ground those two pins again. See if you flash 12 three times then three more to end the diagnostic.

 

grounding means the two most left pins...use a paper clip "U" shape. Note ground one pin to frame. You doing it right?

Jim

 

CEL repaired. Bad ECM. Put in a new ECM and CEL now shines.

Thanks for the help.

 

Great!!!. glad to hear it.

Jim