LAGATTU

Hello everybody ,
I have a 93 Corvette 190,000 miles ,after automatic box overhauled ,and various settings ,TV cable ...........oil sensor ,throttle cable (but is not very stiff now ) ,i "try to use my car .......After 1/4 mile ,rpm engine was hesitating ,RPM going up and down ,but I succeed to be back home ,(I was supposing not enough fuel ° .Put more fuel ,and after 2 miles same thing again,rpm up and down ,some misfiring nand stall middle road ,not possible to fire again .Home I replace opti (AC 4,00 miles )with Petris vbentilated ,coil ,ICM ,finlly no starts.....so I have "played " withy codes erasing ,and I got C 12 only ,sparks at coil and fire in the second (as before) ,so before installed back WP ,many starts in the second.Pump back ,some difficulties to fire ,and then fire .I leave engine running until cooling fans start about 180,rpm 500 as usual,running steady ,and after 20 minutes,rpm up and down ,some misfiring ,and stall again ,since not any starts .Codes are H16,H41,H72 ;After aga
After looking to FSM ,,the conclusion

LAGATTU

The conclusion is ,"open circuit between ECM and ICM.......Another test this afternoon ,code checks ,only C 12 .Try starts ,no ,codes now H16,so my story is not finshed ...If somebody got ideas ..what bother me ,is before opti renewal ,and after renewal ,STILL same problems .Thanks for help............

81c3

Is it possible that when the transmission was rebuilt and reinstalled the wire harness was damaged or pinched somewhere?

JimLentz

Could be your ECM, they do weird things as the solder joints can become intermittent. It happened on my '92 like that and I only had 42K miles at the time.

LAGATTU

Thank you ,for your replies ,

For my repair ,box ,I run with ,about 5,00 miles ;without problems ,and not any miss firings .As FSM ,says that maybe "open IC circuit between ECM and ICM " ,for me it's hard to believe ,,because when you check harness form ECM up to ICM ,it's very hard to see something ,and harness ,is not in contact with engine hot parts .I will check again this afternoon .
After looking to forums ,,I was convince that problem comes from ECM .But before to send to US from France I want to be sure ,money wise ...I will let you know ,later on .news

MatthewMiller

Hzve you tested the wire that leads from the ECM to the ICM for continuity? That would be the very first thing I would check. If that wire has minimal resistance, then it's okay. But if it's infinite, then it's an open circuit and won't work. If it's an open circuit, then run a new wire and see if it will run.

Also, look at the harness where it connects to the ECM. Make sure the little metal connector that contacts the ECM pin for that wire is still physically in the connector. It should not be loose or halfway out. Make sure it looks like all the other connectors.

I agree that it's possible for the ECM to fail, but I would expect more than just the output signal the ICM to have failed if that were problem.

LAGATTU

Hi MATTEW,
Yesterday ,I was not sure ,that I got a true contact with A 12 grey conector .With a verified test ,circuit is open ........With FSM ,various procedures all conclusions , stil the same "open circuit "........My last firing test I had code C 12 --------that's all ................after no firing again ,,C 12 ,H 16 .
I was understanding to install new wire ,between ECM and ignition connector, but I am not pleased to cut wires ,As apparently ,it's seems to be the solution,I will do ,let you know later

MatthewMiller

I understand that this is not the most fun job to do! Good luck. We look forward to reading about your results.

LAGATTU

Hi followers ,
So I did intall a direct wire betwen ECM and ICM ,and I have cut wires ,only remove insulation ,and place a direct wire ,by only twisting around bare location ,but no success.maybe not thight enough ......will try again .I look to maximum threads ,concerning this probem ,and finally.,I found one with strictly my problems,I will take care of these advices ..So this thread tittle is ,"1992 LT1 no start due to short to IC circuit 423.How to find the short " .some news later.