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Help! 92 corvette vats problem

ochenee

New member
Joined
Feb 4, 2013
Messages
4
Location
Washington
Corvette
1992 coupe
Hello all, I have a 1992 vette that i think the vats system is failing, i would like to know how to remove it entirely if possable, problem is it starts, runs fine,about 5/10 min the security light starts flashing, along with a sys flashing in the speedo, then the sevice asr light comes on, all the wile it continues to run fine no problems, until i shut it off, then it wont start back up, sometimes it starts and dies, security light flashes and so on, if i pump the gas pedal i can keep it running, but when i stop pumping the gas, it dies, when it isnt starting it still cranks over fine, ive bought a new pass key, no luck, had the ccm tested and reprogramed, no luck, had it in a shop for months, they couldnt figure it out, sometimes i can diconnect the battery for a wile, reconnect it and it will fir right up and run fine, then the same thing happends,(flashing security light and so on) then i shut it off, and again, cranks fine but wont start, whats up with that, does anyone know out there? All the grounds have been checked out ass well, I think the vats is cutting off the fuel, any help on this would be greatly appreciated! Thanks. Mark
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
When SYS flashes it indicates a trouble code has been
set in CCM.

To find the trouble code you use a piece of wire and short pin A to pin G on the diagnostic connector located above the drivers knee.

obd1.jpg


Turn the ignition ON and the codes will be displayed in the dash cluster LCD.

Module 1 is the CCM
Module 4 is the ECM
Module 9 is the ABS/ASR

From your description you'll probably see a CCM code 41 ECM Serial Data Circuit Loss of Communication.
This indicates the CCM can not communicate with the ECM.

After the problem occurs, shut the engine off. Short Pin A to Pin B.
Turn the ignition On. This method pulls codes direct from the ECM. Codes are displayed using the Service Engine Soon Indicator lamp. Code 12 will flash three times, any trouble codes three times if there are any, then Code 12 again three times indicaticating all codes have been displayed,. If ECM codes can not be displayed using this procedure it would point to a problem with the ECM.

Example for a code 12. Flash pause Flash, Flash. Long pause next code displayed.

92-93 ECM's are known to have bad solder joints/circuit board flex problems which can cause problems like you described. Sometimes you can duplicate the problem by banging on the ECM case while the engine is running.
 
Last edited:

ochenee

New member
Joined
Feb 4, 2013
Messages
4
Location
Washington
Corvette
1992 coupe
I know about the trouble codes, done that, before takeing it into the shop, im sure they did it too, no luck there! Anything else? How do i remove and by-pass the VATS module? Im sure this is the problem, dont want to here about resistors and that, been tryed, i want to rip it out, plain and simple, pain in he ass when you dont need it! Where is it, and how do you by-pass it would be good, thank you...Mark
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
I know about the trouble codes, done that, before takeing it into the shop, im sure they did it too, no luck there! Anything else? How do i remove and by-pass the VATS module? Im sure this is the problem, dont want to here about resistors and that, been tryed, i want to rip it out, plain and simple, pain in he ass when you dont need it! Where is it, and how do you by-pass it would be good, thank you...Mark

The VATS is built into the CCM. It's not a separate module.

So what were the codes?

You metioned the CCM was reprogrammed. That can't
be done unless a new/rebuilt one was installed.

On a new/rebuilt CCM after 100 miles the programming feature is locked out.

Your problem is the CCM is losing communication with the ECM through the serial bus. The CCM is the master on the bus. It polls devices on the serial bus such as the EBTCM, C68 HVAC Programmer and ECM.

The serial bus must be working if the only a CCM error code DTC 41 is set. (That's why I asked what codes are being set).
This would point the ECM being the problem.

As far as I know you can have the Eprom in the ECM reprogrammed to ignore the flag that is set if the key pellet doesn't match what the CCM was programmed for. You also have to enable the starter relay by a jumper wire.

The problem is there is no way to enable the pulsing of the fuel injectors on a 92 ECM because unlike the older ECM's where you could attach an externally generated square wave to simulate the FED (fuel enable disable) signal. You can't do that with the 92 ECM because the FED signal line was eliminated.
 
Last edited:

ochenee

New member
Joined
Feb 4, 2013
Messages
4
Location
Washington
Corvette
1992 coupe
Thanks for your help, so i guess i will just rip the manifold off, with the injectors, and take out the opti spark thats new, and switch it over to the tryed and true HEI dist and a carb, hell, just scrap the car, hell with that?, light a big fire! dance around it like wild indians...yaa sounds good:mad
 

BigJimZ16

Well-known member
Joined
Oct 20, 2008
Messages
925
Location
Portage, Indiana
Corvette
2010 Grand Sport Vert JS Blue
Thanks for your help, so i guess i will just rip the manifold off, with the injectors, and take out the opti spark thats new, and switch it over to the tryed and true HEI dist and a carb, hell, just scrap the car, hell with that?, light a big fire! dance around it like wild indians...yaa sounds good:mad

Or, you could, with the help of the Factory Service Manual, follow the logical trouble-shooting procedures and fix the problem... Might be cheaper in the long run!
 

tmkassin

Well-known member
Joined
May 17, 2009
Messages
271
Location
Macomb,MI
Corvette
2009 LS3
I went through similar issues with my 92. It was the ECU. Python Injectors in California can test and rebuild it.
 

ochenee

New member
Joined
Feb 4, 2013
Messages
4
Location
Washington
Corvette
1992 coupe
Are you saying that the ecm might be bad? I dont understand why it would keep running fine until i shut it off, do they have a website? Thanks...Mark
 

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