Drove the vette last night and it was running fine. (havnt had any problems ) Well this morning I went to start it and all it did was crank. I hooked up my auto-x ray and got a code dtc 42 (electronic spark timing circuit grounded) So I went to my service manual and went to the flow chart on 6e3-a-75 and did the test that they required. It appears that the problem is a faulty ecm or a ecm connector if I did everything correctly. I do have a couple of questions for those who have been through this. 1. when checking for 1 to 4 volts AC between ground and term. B of the ignition coil module connector, is this supposed to be a constant voltage? When the ignition was first turned on it goes up but only for a split second. Then while it is being cranked it is around .3 volts AC. 2. upon testing the ecm connector A, wire 12 with a test light hooked to the battery + terminal, it would not light, but I do hear a clicking coming from the other side of the engine. (around the coil) I then tried a volt meter instead of the light and I do have 12 volts on a digital meter, but it wont light the test light. Any suggestions would be appreciated before I go buy a ecm.


[Modified by Red 86 4+3, 11:15 AM 6/30/2002]

 

TTT

 

Well I was hoping someone would have some input on this. I ordered a rebuilt computer from mid-america. I hope this fixes it!! Ill let you know.

 

red, keep me informed on your progress....I too have a code 42 I'm chasing. My car starts and runs, just not as well as it used to. I've replaced the ignition module, but I still have the code. If the new ECM cures yours, I think I might give a new one a try.....Good Luck!! :jester :jester

 

Mike,

Keep in mind that mine is a 93 and not the 86 I used to own. I followed the diag. tree in the service manual, and the best I can tell its the ecm or it says a short in the wiring. Well I cant find a short so I ordered one. Ill let you know what it does.

 

Well I got it fixed!! I installed the computer and still would not start :cry . So I decided to start from the top again. I am using the factory manual and on pages 6e3-a-74 and 75 they have the diag. tree and diagrams. I decided to try and trace the wires to check for shorts again. I disconnected the battery and pulled the harness loose at the computer and hooked my ohm meter to term. A-12. Then I checked the white wire at the right end of the ignition coil module and had nothing. I then checked the wire marked A "also a white wire" and it had continuity to A-12 at the computer. I then checked with a AC volt meter for 1 to 4 volts on that pin when cranking and I had it. Followed on down and ended up with it saying a faulty ignition coil, module connection or faulty ignition coil module. Well then I ohmed the coil by using the specs I found in a haynes manual I had, but the coil read 8600 ohms. According to them it sould be 5000-7000 ohms. However it did not show a difference between L-98 and LT1 coils. I looked at the connector and it seemed fine. So I decided to chance it and bought the coil module. Fired right up!! Took it for a drive last night "about 50 miles" and it seems to be running fine!! The thing with me misreading the manual, I believe it is a misprint, or I just dont understand the picture of the connector at the module.