Help! 1990 C4 ECM problem

[hyflyer]

I have a 1990 C4. base engine, 6 speed. All of a sudden it would
start locking out my ignition as if it where reading my key chip as

invalid and tripping the anti theft. 5 minutes later it would reset and I could get it started

again. Suspected key switch but it always read good. Then it just shut
down. No fuel pump, no turn over, nothing. Exactly as anti theft would
do but never reset. No codes from the ccm or ecm. Finally I changed
out the ecm and bingo it started and ran fine. I did see to dark pins
on one of the connectors. I cleaned them and hooked everything up and

all was well, for about 2 weeks. This is not a daily driver, but
after approximately 10 starts and stops it did it again. I had it towed
home and again no codes and everything appeared fine. I replaced the
ecm again and bang it started right back up. I am almost afraid to
drive it now as I dont want to get stranded somewhere. I will probably
buy a back up ecm so if it does happen again I can get home. I was
just wondering if anyone might have an ideas as to what to look
for/check that may be a cause for this problem. I do have 107000 miles
on it. I appreciate any help you can give me.
Thanks
hyflyer

 

[Otter]

Had that problem on the 89 I had, by-passed the key chip and never had the problem again.

 

[gmjunkie]

I have a 1990 C4. base engine, 6 speed. All of a sudden it would
start locking out my ignition as if it where reading my key chip as

invalid and tripping the anti theft. 5 minutes later it would reset and I could get it started

again. Suspected key switch but it always read good. Then it just shut
down. No fuel pump, no turn over, nothing. Exactly as anti theft would
do but never reset. No codes from the ccm or ecm. Finally I changed
out the ecm and bingo it started and ran fine. I did see to dark pins
on one of the connectors. I cleaned them and hooked everything up and

all was well, for about 2 weeks. This is not a daily driver, but
after approximately 10 starts and stops it did it again. I had it towed
home and again no codes and everything appeared fine. I replaced the
ecm again and bang it started right back up. I am almost afraid to
drive it now as I dont want to get stranded somewhere. I will probably
buy a back up ecm so if it does happen again I can get home. I was
just wondering if anyone might have an ideas as to what to look
for/check that may be a cause for this problem. I do have 107000 miles
on it. I appreciate any help you can give me.
Thanks
hyflyer

Replace the Ignition Tumbler in the steering column,the contacts are getting worn.
I have cleaned them with electronics cleaner and work for awhile,but usually end up replacing them.

Also,If you have the key on a ring with a big wad of keys dangling and a swinging it wares them out a lot quicker!

 

[kpic]

Also,If you have the key on a ring with a big wad of keys dangling and a swinging it wares them out a lot quicker!

That is excellent problem preventative advice.

 

[DonB]

I agree. Nothing I hate more than a wad of keys jingling and banging into the dash. There are 6 keys on my Vette key ring. 2 for the Vette, 2 for the house and 2 for the garage. My other ring has all the other vehicle keys as well as all the other stuff I don't need when driving the Vette. If need be I bring the other ring and throw it in the console.

 

[DeanM]

1993 c4 similar problem

I had a similar problem with a newly purchased 1993 C4. the owner never used the remotes. When I bought the car he gave me the 2 remotes. When I tried to start the car it was dead. no turnover, but lights and horn. Finally, after about 5 minutes it started right up. On the way home the car suddenly stopped after about 10 miles. I pulled off the road and tried to start it up but it would try to start but wouldn't. the lights at the door handles would flicker intermittently every 20 or 30 seconds. I figured that it had something to do with the remotes so I pulled the batteries out of the remotes and waited for a couple of minutes and the car started. I have had no problems with the car since then, of course, I am not using the remotes. talked to a mechanic friend of mine who suggested that I have the security module and the remotes checked. Will have that done in the near future. Right now the car runs fine so I am in no hurry to have them checked.