dizzysn

So I went to take the Vette out tonight and found that the car would not start. The battery voltage was reading in the single digits, and it's about 4 years old. I decided that I'd just buy a new one while I was out.

I bought the new one, got home and installed it. As soon as I turned the accessories on, it was the same error codes: "Reduced Engine Power, Service Engine Soon, Low Fuel". I tried to start the car, and it immediately died. I noticed the fuel gauge was on E which I thought was strange since I thought it had a half tank or so. Figured I may have a fuel leak.

Ran out and got 4 gallons of 93. Poured it all in and it's still reading empty, though now it won't even crank. The radio doesn't work, the key fob doesn't work, the windows don't work and I don't hear the fuel pump priming.

The diagnostic menu shows "No comm." for everything (PCM, BCM, HVAC, radio, left and right door modules) My first instinct was corrosion on the PCM from battery acid, but when I looked, everything was completely fine.

I'm absolutely baffled here. I'm sure it's an electrical issue, but the car ran perfectly two weeks ago. I have no idea what could have just caused it to go wild out of nowhere. The car does sit for a few weeks at a time before it gets driven, but I've had it for 5 years now and never had an issue doing that.

Any ideas where to start?

BigGun

As it was running fine before the battery died I would start there. A new battery does not always mean a good battery, have it load tested. You do know that on a C5 the battery connections need to be tighter than you might expect. After you verify that the battery and connections are good there a several possible causes that can be investigated.

dizzysn

The battery is definitely good, and connected. Dash lights all work fine, headlights work as well. With this new one the car cranked, started and ran for about a second and then died, while the last one couldn't even crank it.

I also noticed some fog on my windows. Wondering if water got in and onto the BCM.

dizzysn

So last night, I tried to troubleshoot a bit more. Walking up to the car the first thing I noticed is that my key fob worked. I got in the car and when I shut the door, the seat moved forward to it's correct position. I turned the accessories on and had radio, hvac, and no warning lights. Fuel registered at just over half a tank. I started the car and it ran for about 45 seconds (which to me says the battery is good).

Then after that 45 seconds, all the same symptoms appeared. Key fob stopped working, loss of communication with PCM, HVAC, radio, door modules, etc etc. Key fob also stopped working. I'm 100% certain this is an electrical issue at this point.

LivinTheDream

That stinks. Every time mine acts up I review Bill Curlee's posts on grounding, visually inspect wiring, fire up the Fluke, and start methodically troubleshooting. I'm going to guess you already verified it's not the leaky battery/PCM issue that can occur with lead acid batteries.

Sometimes everything is OK, and the new battery has somehow given circuits a fit that trigger codes. Before you get too far, try clearing codes and restarting...

A few weeks ago I replaced the original battery in my son's 2007 Hyundai. I could hear on cranking it was a cold day or two away from stranding him. On first start with replacement it lit up the CEL, the gauges blipped, then it stalled as if it lost base idle setting. I made sure the battery was OK, cleared the codes, and restarted. Been fine ever since.

dizzysn

Bill Curlee is a total life saver! Helped me out with a very nasty electrical bug a few years back. Had me call him up and walked me through a TON of stuff. He wasn't able to correctly diagnose the issue (but not being able to see the car for himself, I would't expect ANYONE to be able to fix it that way), but he gave me the steps and knowledge on how to troubleshoot, and with that I was able to find and fix the problem. He sent me that electrical thread which I favorited. Dude is a total asset to this community.

I also did verify that there was no leaky battery, and nothing leaked down onto the PCM.

I did try clearing the codes, but the car couldn't communicate with any module in the diag menu.

That being said...

Came home today and it fired right up, without a single code and stayed running. Everything worked in the car without a single issue.

Drove it around the block a few times and there wasn't a single hiccup. My conclusion is that water got in somewhere (wiper cowl udders maybe) and leaked onto something it shouldn't have, and over the course of the last two days, dried out. Gotta love GM build quality

jim993

The fact that it cleared on a restart is on my list of symptoms that a failing ignition switch will cause.

I've replaced two ignition switches so far in my 2001.

I have also read that wiring issues in the driver door, wires and adjacent connection near the rubber bellows that is between the door and body can cause communication problems and similar symptoms.

dizzysn

I wouldn't necessarily say a restart fixed it. It sat, and then was better. I think that coincided with water drying out over the course of two days.

I'll have to give a look into those door wires, thanks for the suggestion!

Bill Curlee

You need to do a careful and deliberate water/moisture check. Move the passengers and drivers seat-all the way forward. The carpet on the rear wall will allow you to move it up and you can put your hand under the carpet and feel the carpet underlayment (jute) under the rear seat. If there was moisture/water, thats where it will settle at. If that jute is wet, you have an issue and you need to resolve it. Check both sides!!!

When or If the BCM gets wet, it corrupts the serial data buss. when that happens, the gages spaz out and sometimes the comms between the PCM and BCM get corrupted and the engine wont run. When my 02 ZO6 has this issue, it will crank all day long but the engine will not run. As soon as I clear the issue with the door power connector (serial data buss issue again) it starts and runs just fine.

The BCM can only get wet so many times before the minerals in the water start to take it toil on the board and cause BCM Failure. If you find moisture/water, get it fixed asap.

dizzysn

Thanks for chiming in Bill, much appreciated!

It rained pretty heavily two days ago. I went out and checked around and everything behind the seats was dry, but the passenger footwell carpet felt a bit moist.

No water on the BCM itself, but I think the leak is definitely coming in there, and water got on the BCM last time. Unfortunately it's been freezing, or just above freezing for the last week or so, so I haven't really tried to find where the leak is coming from. Gonna start with the wiper cowl udders this weekend.

Bill Curlee

When you run the AC and or DEFROST, the AC Evaporator makes condensate. There is a condensate drain on the passengers side fire wall. It has to drain outside on the ground or it will fill the air box and drain in the footwell.

TRUST ME. If it leaking from the air box/FAN Motor area,, THE BCM got or is wet inside!!

dizzysn

Oh I know it got wet for sure. The moist carpet confirms it. However I had no idea about the AC/defrost evap being near there. I'll give that a check as well as the udders. Thanks Bill, you're a life saver!

parker1039

i have been thru similar issue, went out to start the car only the arbiture would extend. assumed battery, charged it, no go, pulled starter, took it store to replace, checked good, came back, reinstalled, started worked, no start, reduced power, low fuel, temp went to 260, etc.

separated the bcm/pcm with jumper on star connector, fired one cylinder, unhook the coil packs fires one cylinder..no communication at all even with the bcm/pcm jumpered ...hope Bill sees this

flyingjoey

Why do so many do extensive mods on a already great LS1 engine? Racing answer I guess.. It seems to me many have to go through months without their c5..

dizzysn

The car was a snoozefest when it was stock. You don't buy a car like a Corvette to drive slow, you drive it to race it and beat the **** out of it. And I wouldn't call headers and a cam extensive modifications.

flyingjoey

.. You can go race your corvette on racetrack. Idiots that race
​​​​on public street should get heavy fines ..

dizzysn

Don't recall saying anywhere that I street race, because I don't. Go find another thread to bring your negative opinions to.

flyingjoey

Never said you did, just making statement. Your getting defensive for no reason. I get my share of road rage dummies that think it's ok to race. If you don't like what I saying don't reply. You implied if i have a Corvette I have to drive it fast NOT Slow. I dont race my c5 on the street nor race on track..So going back to the original statement i said quit crying on board if your car all messed up because you modified it raced the **** out of it..

dizzysn

1: You're replying to the thread I started with no help or suggestions.

2: My thread had NOTHING to do with racing whatsoever, so you side tracked the original issue and discussion into a completely separate and irrelevant topic. You're the one who asked why I modified mine, and then speculated that I did it for racing, diverting the topic to something other than the original post. So for you to say that you didn't say I raced is completely false, when in the very post beforehand you said "Why do so many do extensive mods on a already great LS1 engine? Racing answer I guess." Sounds like you can't even keep track of the things you say.

3: Corvettes are made to drive fast. Simple as that.

4: My modifications had absolutely nothing to do with the issue. A water leak did. If you had actually READ the entire thread you would have seen that the issue was solved the next day and that I discovered the source of my water leak.

5: You're bumping a year old thread that had an issue that was solved a day later. You didn't bother even reading the thread, because if you did you would have known it was solved, and known my modifications were not the cause, thus rendering your post pointless. You accuse me of racing, then say you didn't. Suggested I didn't have my car for months. Questioned why I would even bother modifying the car, then get defensive about your driving habits based on my answer as to why *I* modified *my* car. You came in with useless, off topic responses, and get pissy when you get answers you don't like. So how about you leave my thread and to try to post something relevant somewhere else.

flyingjoey

I was just talking in general "many".. it's a fact many beat the hell out of their vettes and mod for performance. The end result they complain and can't understand why they don't have a working car..
Your statement corvette are made to drive fast implies a stereotype street racer's mentality. Maybe you don't mean it that way .. fine.. I was still talking about mods and when I made my statement and you took it in a negitive way.