Welcome to the Corvette Forums at the Corvette Action Center!

Intermittent PCM issues?

badnews

New member
Joined
Aug 24, 2017
Messages
2
Location
Biloxi, MS.
Corvette
1996 LT1 Torch Red
Okay so the history is, its a 1996 Base Coupe LT1 Auto that has sat for 12 years it was having an issue the previous owner couldn't fix where it would idle fine and as soon as you put her in gear she would stall out so he parked her in his shop for a decade anyway. I bought her a couple of weeks ago and So far I installed a NewRockies VATS bypass module, I drained and mopped and scrubbed the tank clean, installed a new fuel pump and sock, changed the fluids and filters and most of the hoses, serpentine belt, new battery, put fresh gas and new fuel filter in and she cranked right up and started I let her run for 30 minuets burning all the cob webs and crude off and shut her down and restarted no less than 6 times during this process each time she started right up without even a full revolution of the crank. after the 30 minuets of running I shut her down and the heater hose looking hose the goes from the radiator tank to the inlet (which I had overlooked replacing) ruptured and shot all over the front of the motor including I am guessing the old Optispark. Went out the next morning and changed the ruptured hose and cranked her over and she didn't fire, she tried (burped a little) to but just didn't get to where she would catch, I went and bought a new Optispark unit thinking that might be the issue, along with new wires, (and discovered why there is a support group for those who have changed wires on an LT1, I am sure most of the skin on my knuckles will grow back eventually) new AC Delco Double platinum plugs, and installed them. Still nothing, I hooked up my Fuel pressure gauge to the Schrader valve still getting 44 psi on the rail, new fuel pump in singing for a couple of seconds when I power the key, even double checked the filter to make sure I am getting good flow through on the new filter just in case I had missed anything in the tank and it had clogged the new filter, I finally went to check the pulse on the injectors with my noid light and I don't appear to be getting any pulse to the injector,s in addition to that when I hook up the OBD2 reader I get Link Error and I tried both my little $100 hand held and my bigger OB2 reader both are getting a link error and here is the really crazy part now It wont start on starting fluid either it was before. I am getting Good solid Blue spark from the coil and out of the spark plug boot as well. I know that the injectors were working just fine the day before because it ran perfectly until that hose blew out. So I am wondering what to do next because I am about to send it in to the dealer to get a new PCM, BCM and a flash. the link error and no injector pulse is really making me think that the PCM is the issue especially after setting up that long in a shop by the beach. Any one have any other ideas what it could be? Any help would be appreciated.
 

Robertwav1

Well-known member
Joined
Jan 7, 2003
Messages
818
Location
Ocala, Florida
Corvette
1993 Blue
Just wondering if you looked at the connections on the PCM since it's suspect. The water or antifreeze went all over like you said. This can affect grounds on the frame rails as well. The beach area, salt water etc., I would think connections, connections, connections. Although the PCM might have an issue, your busted hose sure caused the problems you have since it ran fine before. I hope you find your problem!
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,452
Location
CenCoast CA
Corvette
71 04 12 19
First...don't use ether ("starting fluid"). The suff is very low octane and can damage engines.

Second...best bet is to get the Factory Service Manual and go though the "cranks but won't run" diagnosis.

If you're one of those who tends not to use the FSM, I think the idea "Robertwav1" posted is a good place to start, but there are any number of other places where you coulid have a wiring and connections problem due wetting down with coolant. One place to look is the wires and connections related to the injectors.

You also ought to consider replacing all the coolant hoses.
 

badnews

New member
Joined
Aug 24, 2017
Messages
2
Location
Biloxi, MS.
Corvette
1996 LT1 Torch Red
First...don't use ether ("starting fluid"). The suff is very low octane and can damage engines.

Second...best bet is to get the Factory Service Manual and go though the "cranks but won't run" diagnosis.

If you're one of those who tends not to use the FSM, I think the idea "Robertwav1" posted is a good place to start, but there are any number of other places where you coulid have a wiring and connections problem due wetting down with coolant. One place to look is the wires and connections related to the injectors.

You also ought to consider replacing all the coolant hoses.


I changed them all after that one blew, had replaced most of them before that had just missed that one. I think I might need to replace the wire harness itself the connections at the back of the PCM the plastic shell around the wires is dried out and busted up and now I'm checking all my grounds as well. I use Alldata now is the FSM better? The link error is one of the main things that's throwing me off. I am getting power to the port because my cheaper code reader lights up so its not a cigar fuse issue but you're right I very well could be these wire connections. the harness is old and sat or a long time. I guess anew harness and some fun wiring is next.
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,452
Location
CenCoast CA
Corvette
71 04 12 19
Link error means the tester cannot establish communication with the ECM. There may be a problem with the serial data line.

If Alldata is any good, you will find instructions on how to diagnose that problem. I have had better luck with ACDelco's GMSi which is, basically, the same cloud-based service information GM dealers use.

You can subcribe through ACDelco's TDS site at ACDelco TDS
 

Toms007

Moderator
Joined
Sep 24, 2004
Messages
6,455
Location
Southwest Kansas
Corvette
2007 Atomic Orange Coupe
Badnews, I would like to welcome you to CAC! :w As you have already found, we have a lot of people here who are very knowledgeable and willing to help you get your 96 back on the road. I can see that you are in good hands here, so I'll back on out. :thumb
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Parts/Accessories:

Vetteskins

Advertise with the Corvette Action Center!

Double Your Chances!

Partners

Top Bottom