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Long time member but mostly lurk. I found some topics through searching but nothing exactly like my issue.
My 2002 C5Z sits for long periods at time. I don’t keep a ton of gas in it for this reason, only put $15-$20 in it. Also stays on a battery tender.
Last drove it a month ago or so.
Went to drive it yesterday and it cranked but wouldn’t fire.
Had somewhere to be so didn’t mess with it much until today.
I tried carb cleaner in the intake to see if it was a fuel issue and still nothing.
Battery started to die but even while hooked up to the cables I couldn’t get it to fire.
When I turn the key to on it says: service engine soon, low fuel and reduced engine power
When I access the diagnostics it says no communication with all modules.
I’ve had the car for 15yrs, I’m the third owner and it only has 26k miles on it. I’ve never had any issues like this. It’s been very dependable. Years ago I had an issue with the PCM getting wet, crack in the housing, but it would just go into limp mode until it dried out.
My first guess would be failing battery.
When it's been off the tender for a couple hours what voltage are you measuring at the battery terminals? What voltage is showing in the DIC?
Could very well be the battery, have it load tested. If your car does have a true no comms problem it will crank but not start because the various modules all communicate on a single wire and if that network fails the PCM and BCM will not allow the car to start.
I guess I just never thought it would be the battery since it sits on a tender but the fact it does so quickly when cranking makes me suspicious. I’ll get it tested
11.5v is less than 20% of a 'fully charged' battery (this is one example, chart is a little ways down the page). Load test should tell you what you need to know. If it's questionable I'd start by replacing the battery first. If you're still having trouble after that at least you've eliminated one potential source of the issue.
Last edited by Dads2kconvertible; Feb 26, 2024 at 11:07 AM.
So obviously something is not allowing the car to start, relay buzzing means low voltage across the relay coil. Can you hear the 2 second fuel pump prime when the key is turned to the run position?
So obviously something is not allowing the car to start, relay buzzing means low voltage across the relay coil. Can you hear the 2 second fuel pump prime when the key is turned to the run position?
sorry been tied up with work then family stuff all day
just got in the car and when you turn the key to the ON position you definitely here a humming noise, which I would think is the fuel pump priming.
I also should note, after I “fixed” it ~3wks ago by replacing the IGN relay, I drove it then next morning to and from my sons little league game, roughly 40mi round trip.
I wasn’t easy on it either. One time when slowing down the rpm dropped out but it never stalled, caught right back. Other than that, zero issues with it.
The fuel pump only turns on for 2 seconds when you first turn the key to run. Sounds like the car has a true no communications problem since it will not start. There are two connectors next to the BCM which contain metal combs which connect the seriel communication line from all the modules. You can remove the combs and connect a wire which will connect only the BCM and PCM and see if the car will start. Search on this site for more details.
The fuel pump only turns on for 2 seconds when you first turn the key to run. Sounds like the car has a true no communications problem since it will not start. There are two connectors next to the BCM which contain metal combs which connect the seriel communication line from all the modules. You can remove the combs and connect a wire which will connect only the BCM and PCM and see if the car will start. Search on this site for more details.
yes the fuel pump noise is only for 2 seconds then stops.
I’ll try to look into the BCM issue this afternoon.
The Ignition switch contacts send 12v to a couple of relays whose contacts send power to the various modules. Your no communications could be the result of either the BCM or PCM not being energized, you will have to have a wiring diagram to find what wires supply power to both modules. The car may still have another problem causing the seriel data buss to be non functional.
One other problem is the car is park about as close as I can get it to the wall in my garage. Backed in. It’s my effort to keep it as far away from kids and their stuff, but makes it really hard to access the passenger footwell and BCM. Or to check both doors for loose wires.
just so odd to me that I could drive the crap out of it and it run great after replacing the IGN relay and then it just do the same thing all over again.
is their anyway to test the ignition switch, without removing it?
Won’t start and getting no communication?
