My cammed 2001 c5 has had intermittent start issues. sometimes it will start and turn off. or crank and idle and then suddenly shut off. Usually after a couple cranks or giving it gas it'll run just fine and I can drive it for a long time.

All of this led to this past week it completely shut off on the road and I rode the clutch into a safe spot. started right up and idled fine for 1-2 mins then shut off. then it would crank + idle only if I hold the key in a certain position. My partner was with me at the time and shifted for me as I held the key in a half crank position limping the car home so that was a fun bonding experience

basically the car cranks and idles fine AS LONG as the key is held to a certain position and it will idle as long as the key is held. I have researched the topic and replaced the ignition switch with a brand new OEM GM one from autozone which did not fix the problem.

Next order of business is getting 2 new keys made (measured and ordered correct key #)

what else do you recommend in diagnosing this issue? My friend believes it is a lock cylinder issue but I am curious to know if that would actually be the underlying problem

thanks for yalls help

 

I recommend first to disconnect this black plug close (first photo) to the ignition switch location .
Connect a multimeter in ohm (resistance reading) to the two pins in the plug
These two wires come from the the sliprings (second photo) reading the resistance in the ignition key .
If the sliprings are weak or dirty the resistance readings will be unstable/wrong and outside acceptable range (last photo)
Try to clean this sliprings and increase the slipringpressure to the key by bending the springs carefully .(or replace it if neccesary)

 

It seems clear that the Ignition lock cylinder is the cause of the problem, because of having to hold the key in a certain position that allows the car to run. I also have to say that supposedly new OEM ignition switches can be bad right out of the box, most of them are Made in China.

 

As mmartinez noted, new ignition switches, regardless of brand, are chinesium. I’ve got one on my bench that had excessive voltage drop right out of the box. Inside, the contacts are misaligned and had oxidation on more than half. I cleaned the original switch contacts with better results.
As far as I know, I’ve yet to have a problem with my lock cylinder, but I cleaned the cylinder and contacts with MAF cleaner (leaves less contaminants than contact cleaner) while working with the switch.

 

Good suggestion, and this information needs to be understood as part of the troubleshooting process. While the BCM does monitor the key while the car is running ....which you have definitely proven, I have never seen a intermittent lock cylinder cause a complete shutdown of the engine. Sounds like the OP has two problems here.

 

What would be the other problem? I actually googled a ton before making this post and my experience is fairly uncommon but does exist. Most of the threads say ignition switch, 1-2 of them said lock cylinder. and I believe 1-2 also said some relay in the BCM. Do you think this is a security system issue and the relay needs to be replaced or is it mechanical and within the lock cylinder?

 

My vote is for either the lock cylinder or Ignition switch, many people have had to open brand new Ignition switches and bend the tabs inside. There is a sticky thread at the top by Bill Curlee detailing the repair. The fact that you have to hold the key in a certain position for the car to run is clear evidence that it's the switch.

 

A ton of googling is no substitute for actual checks with a DMM/Test light to verify what is going on. Have you done any troubleshooting that you can share?

Aside from the mechanical function of accepting the key, the lock cylinder serves one function: to provide a key resistance value to the BCM. From there the BCM does the following:
1) Enables the TDR
2) Sends a password to the PCM to enable fuel
3) Works with column lock (according to the FSM but I have never seen it clearly explained)

So the BCM either reads the resistance from the lock cylinder or it does not. If the value read is not correct, then TDR is not enabled, and the engine will not crank.....let alone start and run with the key held in a certain position.

Now, if there was something really funky mechanically with the lock cylinder that may influence the position, but your voltage checks will confirm that.

 

I recommend you to inspect the connectors on the ignition switch C1 and C2 .

Do some measurements on each connector pin and verify if the voltage using a multimeter or even better use a scope with at least 4 channels
Good measurements will expose faulty ignitionswitch contact

I assisted a C5 owner last summer who had intermittent start and stop issues for a year and more.

After a replacement of the fuelpump relay recommended by me he also wanted to reinstall his old ignitionswitch replaced by a workshop previous during his troubleshooting nightmare with this car .
After the old ignitionswitch was reinstalled he discovered a loose connection on one of the RED wires .

He made this connection solid and the car has been acting normal since this point.

If the key resistor is loosing contact with the BCM it wil not cause the car to stop , only prevent starting of the car

 

So replaced with new oem switch (also checked with another new oem switch just in case) , new oem lock cylinder and had 2 new oem keys cut. same issue

we were able to jump the fuel pump and that fixed the problem immediately

removed battery, cleaned area with MAF and a vacuum

one wire was completely chewed through on SP122 but it never presented a problem before. my car is garage kept so this probably happened with the previous owner.

checked g105 (another thread said his was loose and tightening it worked) but mine was already tight

further threads say it could be the fuse box itself and I already ordered a new relay just in case that’s coming tomorrow

Open to more ideas at this point

 

'we were able to jump the fuel pump and that fixed the problem immediately.' So it fixed the problem then came back??

 

Update:

After replacing the key cylinder the problem persisted so did a ton of research. no priming unless the relay is jumped.

Another symptom is persistent low oil level warning on despite having full oil

Real issue was the 122 splice pack. Two of the holes had about 900 ohms of resistance and there was a wire that was chewed threw. cleaned the area (luckily the inside was pristine clean) and resoldered the wires with insulation. grounded the wires to the ground in the battery tray (cleaned and put on dielectric grease). wrapped heavily in electrical tape and dielectric grease around that as well. This is a common problem with a lot of cars apparently just from the number of threads on the forums. cleaned the battery and electrical area overall

voila, car primes, starts and https://www.corvetteforum.com/forums...se-manual.html - this disappeared as well. Got full functionality back and enjoyed a couple of days without any warnings

Low oil level warning came back and I added a quart, went away. Next order of business will be to change the sensor and inspect the wire. Thank y'all for helping throughout the process