So this issue with code H16 started back 5 months ago? That would have turned on your SES light and yes turned on both fans... it did this once back then and not since until now?

There are two signals from the opti-spark that go to the ECM. One is a high resolution pulse (high res) and the other is a low resolution pulse (low res). Everything is not normal if you are getting this code (it means the ECM is having issues with the low res signal...can be the opti, the harness or *maybe* (unlikely) the ECM itself, maybe bad grounds). The ECM uses the two opti-signals to know where the engine's rotating assembly position is so it can fire the correct injector bank at the right time and adjust spark timing etc... I know the engine can *run* without one of the signals but I thought the low res one was the critical one. Without both signals the ECM cannot even tell the engine is spinning.

Ok, so it wasn't starting or had running issues, and the mechanic replaced everything electrical related? Did they do any diagnostics on actual errors? (based on your pic: icm, coil, opti, EGR and several other things were replaced... ONE of those things may have been the issue [and perhaps not even the opti])

I think current consensus is the Petris optispark unit. i have that installed on mine without issues but granted not too many miles on it.

Do you have some mechanical ability yourself? Are you able to inspect the opti harness and make sure the connectors are clean and tight? Are you able to clean up and inspect grounds? If you have the FSM are you able to follow the troubleshooting guide for code 16 (you should do this before any further mechanical work)?

 

Ho visto il codice h 16 perché 5 mesi fa si è accesa la spia tagliando motore e il motore girava a gonfie vele e il meccanico mi ha cambiato EGR perché era molto sporca e forse ICM poi il motore girava bene ma il codice 16 c'era sempre . ma avevo sostituito l'optispark e la bobina da un altro meccanico che non aveva nemmeno gli strumenti di diagnosi (tech 1 ad esempio) e aveva fatto anche altri lavori (pompa freno) ma la spia motore service ogni tanto si accende si è acceso e poi si è spento e mi ha detto che l'ECM a volte non leggeva l'optispark, era normale, non ero molto tranquillo con questo meccanico e ho cambiato officina. ma neanche il secondo meccanico ha gli strumenti diagnostici. ho prestato il manuale FSM che ho comprato su eBay,

 

non sono un
meccanico But I am passionate about American cars

 

i hope i wrote everything correct my english language is not perfect

 

the code 72 in module 9 what it indicates?

 

My understanding is module 9, h72 is not an issue:

https://www.corvetteforum.com/forums...post1603353269

 

for code 4. h16 which chapter should I look at on the manual fsm? and code 9.h62?

 

I have this manual

 

I disconnected the battery and checked the sensors then reconnected the battery cleared the codes. h 62 and h72 I started the engine the cooling fan started immediately and the SES light came on I rechecked the error codes and I have on module 4 h16 and h43 on module 9 no codes

 

I mounted an old ICM and the SES indicator light turned off and also the cooling fan does not start anymore but is it normal that the ICM sensor is very very hot even if it is not fixed to the engine?

 

Hello, where I can find the chart in the FSM?

 

I solved the problem after months I repaired the ecm. Greetings to all