antonioe202

1994 Corvette 6speed boltons and cam.
Now the car will start and run perfect all for about 3 seconds and then it will die like the key was turned off. I can do this all day long and will do the same thing. Ive tried unplugging ECM and battery multiple times. Still no luck. I took the ccm in the dash out and looked in the circuit board for any thing unusual and found nothing. Looked at the connectors of both the ccm and PCM all checks out okay.

When I checked for codes using the jumper trick, I get an H41 and C41 for the ccm then I get an error for the pcm Module 4, no Codes for module 9. I believe this is because of the code 41. Not exactly sure what to do next, ive looked at other posts and none of them led to solution. Any help on which direction to go next would be great, it has to be something dumb because the starts quickly and runs great for the time that it does before it dies. I believe my issue is since both CCM and PCM are not communicating the ccm is not telling the pcm to fire injectors upon start up to allow the car to continue running.
Thanks in advance Antonio.

WVZR-1

This car ran well UNTIL you did what? You didn't just walk out one morning turn the key and this was the result OR maybe was it? Does the CEL stay on STEADY with key-on but no attempt to crank?

JimLentz

If you have the FSM I would be checking continuity for the async line between the PCM and the ECM. That would show if the line is open between the two. The other possibility is it is shorted to ground somewhere, which you can also check with a multimeter. Also check the connectors on the ECM and make sure they aren't oxidized/loose.

BlowerWorks

Do you have fuel pressure ? Sounds to me like your oil pressure fuel pump switch is not making. This switch keeps the fuel pump running after the PCM relay signal goes away - 2 or 3 seconds.

GaryDoug

Since he is talking to two other modules, I doubt it is a short. Your last suggestion seems to be the best and most likely to produce results. Check the connectors on the pcm, particularly connector D. Then check continuity from D.29 and D.30 on the pcm to pin 9 on the DLC. Should read near zero Ohms.

antonioe202

Sorry I should have explained my issue a bit better. Few weeks ago I was driving the car going through the gears. All the sudden the car dies out of no where, while rolling I attempt to start the car, I then get no power on the dash nor starting. Get out and wiggle the battery terminal and hear everything come back on. Went to start the car, nothing. Pushed it to my buddies house and checked for spark, nothing there. Long story short I swapped the opti,coil,and ICM. All that for nothing becuase it still didnt start. Turns out the whole time I was looking in the wrong fuse box and found the blown coil fuse...LOL. Car fired right up after then died within 5 sec. Did this about 20 times with the same result. Cleared codes and tried again getting the C41 and h41 in module one and err for module 4 and no codes for 9.

antonioe202

CEL comes one when priming injectors, then turns off while cranking, while running and even after it dies.

antonioe202

Should I remove the pcm from the car to check the D29 and D30 to pin 9 on the DLC? The OBD1 port correct? Im not sure if my volt meter wires are long enough to reach while still in the car.

Ive paid for the PCM 4 less VATS Delete, mail order tune but havent sent the pcm out yet so I will check the connections. My hope here is that the only thing keeping the motor from running is the CCM not telling my PCM to fire injectors, If I completely get rid of that conversation between the 2 possibly it will stay running.

Thanks For the quick replys

antfarmer2

Test the coil and icm and fuel pressure.

GaryDoug

I don't know if you have to remove the pcm to get access to the connectors, maybe. I'm not familiar with the Y-car arrangement. But otherwise, the pcm doesn't have to be out to do the test. Yes, the DLC, data link connector, is the OBD1 connector. You can extend one meter wire with just about anything, even a wire from an old lamp cord.

Typically, the LT1 pcm does pulse the injectors for a few seconds even without the fuel signal from the CCM. Then it shuts off afterward unless that signal is received. I think you are on the right track by suspecting the communication error to be responsible for the problem with no-starting.

TorchTarga94

Did anything eve materialize out of this? Did you end up finding the culprit?

antonioe202

Hey so I ended up getting the pcm tuned deleting the vats and the car fired right up. Unfortunately after the car developed all sorts of issues. And now I'm chasing a dead cylinder. Looked in the valve covers to find all kinds of metal pieces. But the strange thing is the valve springs all look to be okay and I can't seem to figure out what these parts are for.

antonioe202

Indio Monk

Wow! Never seen that before.

antonioe202

Hate to dig up an old thread again, but all that metal I found in the cylinder head were pieces of my valve spring dampeners along with all the valve seals etc. Also found the dead cylinder with a temp gun finding out cyl exh valve spring snapped in two pieces.. After many oil changes and even sticking a camera through the oil pan to see whats going on, the car is running again now with .630 lift lunati spring kit that came with every thing needed for the install. Highly recommend for the price cant beat it.

After that I drove the car for about a week, doing the usual fun stuff, car meets, Wot pulls, etc. Then my next bombshell lol the gear that spins the waterpump shaft inside the timing cover stripped causing the car to overheat, badly. Like 250 degrees before I caught it :/ Hopefully it wasnt too late. No signs of water in oil or any thing like that. So I took the easy way out and Bought an EWP from jeggs and that install even came with its list of gremlins lol. Whats next? Knock on wood.Thanks for all the help and insight guys. Hopefully tomorrow shell be out on the streets making mustangs mad again lol.