K-Spaz

Well, really EVERYthing no comms.

So I've got my car running fairly nice w/new motor and trans, etc. Want to tweak the alignment so I take the car to work this morning. Get here, shut it off, open the overhead door, start it up, bring it in. Did some checking on the suspension quick before jacking it up. All ready to put it up on ramps. Turn it back on again, I get messages saying Reduced Engine Power, Check Tire Pressure, Fuel Low, and a couple others. However ,the car starts and runs as normal. So, I drive it up on the ramps, shut it off. Figure, I'll get to that later. It's got to be something simple. In hindsight, should have put the charger on then, but didn't.

Add some positive caster to the car, finish up the alignment. A couple times in between I've hit the key and yep, sure enough same messages. There's no codes. I get No Comms for every single module on the car. No trunk release, no courtesy lights, no nuthin! Do have dash lights.

But the car starts and runs??? Now I have not tried to drive it and I suspect that won't work out very well. I've put the battery charger on the car, in spite of the fact that the volts are fine (check with a meter, no gauges in the car work) and there's enough battery that the car starts. With ease I might say. Fires right up.

I found two threads discussing this issue. Doesn't look like either is going to help, though I'm going to check the seat module issue very soon. One thread mentioned that. I don't have a warm fuzzy feeling about it though. Sounds like almost anything can cause it.

Any ideas out there?

Here's the two thread I found. I'm going to search again in Tech.

https://www.corvetteforum.com/forums...ont-start.html

https://www.corvetteforum.com/forums...t=pcm+no+comms

Edit. Just looked in tech, there's a gaggle of threads there. Looks like a heap of reading.

K-Spaz

Had the charger on it for probably a half hour. Battery is not taking much charge, 4A, but it's got plenty of power.

Disconnected the battery for a minute, checked fuses in both fuse panels. Reconnected the battery. Courtesy lights were back. Figured it was fixed. Hit the key, no messages, everything is back in action.

I really don't have a good feeling about this.

I've been smelling a electrical burning smell any time I have the hvac fan running and figured it was that resistor piece of crap dying in this car too. Just had the same issue with my truck a while back. Got a replacement but it was for a manual AC, mine is DZCC. Just checked and it won't fit. Didn't look at the resistor yet but I suspect it's burnt and that's what's causing the smell.

I did leave my HPTuners MPVI plugged in last night and I know it to drain the battery. But, the car started and ran fine for 12 miles this morning, and started twice again just fine before giving me any messages. How crazy is this.

Pounder

ignition switch ??? (have their share of issues)

K-Spaz

I have no idea. I did buy one though, it's on the way. But can't say if it could cause this or not. I certainly get the security light often enough. But it's never ever caused an issue for me. Drove it home and never saw a light. Go figure.

~Josh

The fact you charged the battery and and things were good is a clue.
So... you shut off the car to raise the garage then cranked again, drawing power and had a problem. Checking while on the lift only draws more power hence continued issues.

Then... you charge it a half hour and voila no problems. Start simple by taking the battery to have it tested.

K-Spaz

Yea, but is it not odd that even in a depleted state, it starts the car perfectly? I'm not disputing that you may have a point, obviously something happened. I can't say if it was fixed by disconnecting the battery or charing it. Didn't try in between, not that I recall now anyway.

But yes, parked outside the door, came in and turned on lights, got things ready. Opened the door and brought it in. Again, turned off, checked some alignment measurements and then put the ramps in place, started it and got the message. Drove up on the ramps anyway, figured wth, may as well get it up in the air. Turned it off while showing the Reduced Eng Power.

I've had the battery dead enough that it would not start the car and never had anything like this. Once, I left the interior lights on, another I killed it with the MCPI interface plugged in for days. Both times, it just acted like the battery was dead. I didn't get messages. This time, all hell broke loose even though the car started just fine.

~Josh

Could've just gone haywire (ghost in the machine) due to a voltage spike and disconnecting the battery reset everything.

There are some electrical gotcha areas on the C5- the harness that goes into the drivers door, the hazard switch, the turn/multifunction switch and ignition switch. All have caused gremlins and threads showing them all at times as the culprits.