Hi,

I have a 1992 Auto. I've posted before about starting issues, and still has not been resolved. Here is what I've done, and checked so far:
- Rebuilt ECM by SIA
- Reinspected ECM 2nd time by SIA
- Purchased new PROM by ZIP
- Installed correct VATS bypass
- No ODB1/CCM errors
- New battery, 6 months old
- Cleaned ignition key barrel
- inspected for obvious faulty wires under dash
- Double and triple checked all fuses, in both fuse boxes

The car will not start, that is no crank or any other activity, if there is no security light present. The SERVICE ASR light will appear when the key is in the start key position but the car isn't running. The SERVICE ASR appears when the cars SECURITY light isn't present. Also, when the car finally runs and the ASR light appears, I know that the security light isn't present and will then not start. The issue with the ASR light appearing is what lead me down the direction of the ECM and PROM needing attention.

I believe that, in order for the car to start, the security light needs to be present. So, how exactly do I troubleshoot that the security is working correctly?

When I get into the car, if the courtesy door lights and security light isn't present then it will not start. So, the VATS or any other system really isn't at play the moment I get into the car.

I will often just sit in the car, not do anything, and the courtesy lights and security light will appear then I know I can start it up.

I'm at wits end!

 

The security light does not to be on for the car to start. I have a sticky door swith so when I open the drivers door the courtesy lights don't turn on nor does the security light. This has no effect on starting the car.

That said, the lack of courtesy lights and lack of security lights when the car does not start would lead me to belive there is an issue with the CCM.

The CCM:
Sends the command to light the security light
Provides a ground to the courtesy lamp relay when either door switch is closed (door open).
Provides ground to the starter relay when it sees a proper resistance value from the key pellet.

 

Should I receive an error code from the CCM?

There has to be a correlation to the security light?! I know that if I have a solid security light in the ignition switch then that means the VATS is in play and will not start. I've never been able to start the car without the security light. I also have a faulty switch on the passenger side, so I understand what your saying. But if the car can start with the security system offline, then what good is the security system?!

I've looked into accessing it for the purposes of replacing or inspecting obvious wires of issues. It's a PITA to get to. Is there an alternative to bypassing some of its oversight so I can simply start the car?

 

Have you pulled codes? If so how? The paper clip method should be all that is needed

Have you cleaned and inspected all grounds (particularly main engine and the one in the driver footwell)?

Do you have a FSM and have followed diagnostics for ECM to CCM comm? A short on the bus either from a bad wire or failed component could cause problems...ASR is on the same bus if I recall

Have you checked for voltage drop at CCM power and checked positive fuse block for full voltage?

CCM does more than control starter...it tells the ECM to enable the fuel injectors...so even if you bypass to force crank if the issue is a comms issue it will not start (it may stumble but the ECM will not enable FI).

When I had ECM failure it would always crank (and always start cold), but when running and hot security light would blink, service ASR would come on and the digital dash would have issues/blink SYS, finally it wouldn’t start hot due to FI disablement...yours sounds different...

 

What about your shifter switch? The start wire goes through that switch in park and neutral.
Just throwing that out there.

 

I have checked for codes using the paper clip metbod and I do not receive any errors.

I don't have an FSM, nor have I checked all grounds. I have checked the one close to the oil filter by the engine, but that's about it. I didn't know there was one by the driver footwear. I also have an intermittent REST INFL light, so perhaps the common ground is there.

I checked the voltage at the fuses and all seems fine.

So for clarification, it doesn't crank. Each time it cranks, it will start. So, I don't think I have FI cutoff issue.

 

I tried to jiggle and attempted to start it in both park and neutral. No changes, still won't start.

 

You've spent a good many $$$ without having an FSM for proper diagnostics. You need one!

Your 'CRANK' issue is very likely related to issues in 'CRANK' circuitry - starter? Lots to check!!!

 

It will crank and run fine, if the security light is present. I know that there may not be a correlation, but I'm just stating the symptoms that I experience.

 

I suspect a ground issue.
I would start in the engine bay removing and cleaning every ground you can find. Then get under the dash and check all the connectors.
My friend has a C7 that would always blow the backup lights fuse. We found a wire trapped under a bolt at the rear bumper cover.
I bought an Acura that the dash would not light up or the windows roll down. Found the positive wire for the cigar lighter had been grounded under the center console.
Just never know what you'll find in a used car.

 

This post is exactly what I'm going through- https://www.corvetteforum.com/forums...-in-91-c4.html

I have ran through the diagnostic steps about the CCM in the FSM.


I checked all the points in the diagnostic steps, and the ground and power access ports are operating correctly.

At this point, I am suspecting the CCM per all the YES responses on the left diagnostic steps.

If anyone has a place that you recommend for CCM repairs, please let me know.