92 LT1 Service engine light, but throws no codes
Thread Starter
Intermediate
Joined: May 2003
Posts: 28
Likes: 0
92 LT1 Service engine light, but throws no codes
Hi, Looking for some ideas where to search now. My 92 LT1 6sp has been running really well until recently. The symptoms I have which have indicated a limp home condition according to the FSM is: Start car, within 3 -4 secs, Service engine soon light goes on, Both fans begin to run. I followed the FSM and it looks as if the book is saying its the ECM. I have an OB1-scanner, does not pulls up no codes after startup. C-12, H36 every time I use the paper clip technique.
When driven other than the light and fans, car runs strong, no diminished performance
Any other ideas to test or check?
I went through each of the sensors. Battery looks to have a good voltage. Although from my past searches some have notes that using a battery tender sometimes causes problems. Not sure if that is true?
Opti, wires, injectors all new.
Any help is greatly appreciated
When driven other than the light and fans, car runs strong, no diminished performance
Any other ideas to test or check?
I went through each of the sensors. Battery looks to have a good voltage. Although from my past searches some have notes that using a battery tender sometimes causes problems. Not sure if that is true?
Opti, wires, injectors all new.
Any help is greatly appreciated
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
Two quick thoughts.
1. Coolant temp sensor in water pump bad or disconnected -- check what the digitial dash coolant temp says..
2. bad ground connection -- especially the one at/near the battery ground cable connection (i.e. driver side bell housing).
1. Coolant temp sensor in water pump bad or disconnected -- check what the digitial dash coolant temp says..
2. bad ground connection -- especially the one at/near the battery ground cable connection (i.e. driver side bell housing).
Thread Starter
Intermediate
Joined: May 2003
Posts: 28
Likes: 0
Thanks,
I did disconnect and start and no change. This gauge is reading properly, Many years ago this sensor was off the charts and I remember it affecting the idle and general drivability.
I'll check that ground, thanks, I'm thinking of taking battery out and getting it checked. The volts check out but I think I need to start ruling stuff out.
I did disconnect and start and no change. This gauge is reading properly, Many years ago this sensor was off the charts and I remember it affecting the idle and general drivability.
I'll check that ground, thanks, I'm thinking of taking battery out and getting it checked. The volts check out but I think I need to start ruling stuff out.
Le Mans Master
Joined: Mar 2001
Posts: 7,999
Likes: 14
From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
Cruise-In III Veteran
Cruise-In IV Veteran
St. Jude Donor '12
Did you short the ADL pins to have the codes displayed by module on the dash?
Got a FSM handy? The procedure is there to pull the CCM, ECM and other module codes.
Got a FSM handy? The procedure is there to pull the CCM, ECM and other module codes.
Thread Starter
Intermediate
Joined: May 2003
Posts: 28
Likes: 0
So Start car, within 3 secs light goes on, both fans stay on. Shut down car, Short the ADL, and the I see C12, H 36, or running normal
And yes I have the FSM, and while following that it leads me to trying a faulty ECM, not sure which page that was in the second book.
Le Mans Master
Joined: Mar 2001
Posts: 7,999
Likes: 14
From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
Cruise-In III Veteran
Cruise-In IV Veteran
St. Jude Donor '12
Yeeccchhhh
Where do you live?
Start looking for another ECM - they are scarce as hens teeth.
Over at the guru there was a guy that had good results with RockAuto's rebuild service.
I keep a second ECM around for just those places in the FSM that say "ECM"
Where do you live?
Start looking for another ECM - they are scarce as hens teeth.
Over at the guru there was a guy that had good results with RockAuto's rebuild service.
I keep a second ECM around for just those places in the FSM that say "ECM"
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Heck, just for fun, open the access panel on your ECM and make sure the MEMCAL is fully seated in its slot. If it's not that can also cause limp mode issues. But yeah, chances are you're looking at an ECM repair.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
1st Gear
Joined: Oct 2020
Posts: 1
Likes: 1
Hi, yes this was my thread from 2012. From my recall I determined the Optispark while functional was starting to show signs of breakdown. This was my second optispark and like many of us it was a faulty Ebay Delco unit. I bit the bullet and bought a third Delco from Summit with an understanding it was a remanufactured Delco but Summit at least offered a year warranty.
That fixed the problem. I also retrofited a MSD cap and vented it. Worked great until I sold the car in 2017. Great car.
But as many have said the ECM was a 1992 only model which is a nightmare if you had to replace or service.
That fixed the problem. I also retrofited a MSD cap and vented it. Worked great until I sold the car in 2017. Great car.
But as many have said the ECM was a 1992 only model which is a nightmare if you had to replace or service.