Hey guys - got an issue with my C5 Z06
To compound the issue I'm in the UK so limited service options over here.

Started a couple of weeks ago.

Hadn't driven it for a few weeks. Alarm wouldn't respond and the doors were unlocked. No dashboard lights, engine wouldn't turn over.
So flat battery - which is odd because never had an issue before and it's a newish Red Top Optima battery.

Stuck it on trickle charge for 24hrs and then the car would turn over but not start - engine reduced power warning on dash and service soon.

So the next day stuck in a new battery and everything is OK.
Driven the car regularly for the last 3 weeks but then had it on the driveway for the last 7 days without using it

Got in the car yesterday - same thing. It's dead. Car wouldn't start, no turn over. Tested the battery and it was reading 11.8v - which I'd thought would be enough to turn over ?

Brought the battery in for 24hrs of trickle charge - battery fully charged 100% healthy. Put it back in the car and get the same series of errors. Car will turn over but immediately dies.

Any ideas ?

 

I should add that I've got a Diablo Predator Tuner and if connect that up it can't connect to the ECU system.

 

bump !

 

unhook the batt for at least 1 hr, hook back up and see what happens then. If it does it again more than not is the your tune, put the stock tune back in.. Robert

 

Thanks - I'll give it a go in the morning - guess an hour or 10 hours makes no difference ?

 

My $0.02 worth...

As many people have realized, the parasitic draw of a C-5's computers will drain a battery in 10-12 days, if the car is just sitting. This, of course, is if the battery is good. If the battery isn't all that new, it will drop off more quickly.

I think you need to disconnect the battery for an hour, as already suggested, to let the BCM go to a "neutral" state. At the same time, put the battery charger on the battery. You need at least 12 volts in the battery to "fire up" the BCM properly, I'm told, so if you can't get the battery to that level, I'd try another battery.

Good luck!

 

Thanks - I'm leaving it overnight.
Battery was running at 12.8 so should be fine in the morning.
I hope !

Had the car for 6 years - trouble free really and it's a great car. So hopefully I can get to the bottom of it

 

I have never had luck with a optima battery AFTER it went dead. Its not like a regular battery where you can charge them and be fine with the plates inside of them. The optimas are gel filled and dont handle recharges well in my own experience. Try a regular battery and see if thats better.

 

I have let my C5Z sit for about 5 weeks with out starting it, and it started up fine with no problems at all with the battery.

I have heard that Optimas do have problems from time to time, and from the price of them there shouldn't be any problems.

 

Thanks GenerationX & Ice95z

Yr 100% right about Optimas - the don't seem to be able to recharge fully after going flat and for the money, you'd expect them to be the best thing since slice bread.

 

So the car did start this morning.
However, it had the following errors - Service soon, reduced engine power, It's showing no fuel, no gauges.
The DIC codes are all No Comms errors. I can't clear them either.

Went for a short drive and the car does seem to be running OK - but alarm/windows etc do not work.
So seems like it's either a ground issue - or the BCM unit is screwed !

 

Any hints or tips would be greatly appreciated
Thanks

 

I'm in UK so I feel your pain. Red Tops are hard to recharge if you drain them completely. I'll dig out some advice.

Don't think computer at this stage. You have a drain if its killed 2 batteries. I suspect its an easy fix once you find out whats causing the draw. Check out the normal problems at the end of my previous post.

Identifying Battery Problems
The C5 eats batteries unless you take some regular precautions. If your battery continually dies its either the battery which is on its last legs or something on the car.

You also need to look at how you use the car. Is it a daily driver? If so the battery should be getting a good top up every day so you may have a problem.


Is it a DD but you do short trips? If so you'll be taking a lot out of the battery every time you start. For a short trip, say less than about 20 mins, you won’t top it off properly. Eventually it'll drain.

Is it a weekend car. If so, this takes a lot out of your battery. There’s a 20MA drain even dormant. If you don’t drive the car for a reasonable time every week or so, it'll kill the battery. In this case you really do need a battery tender.

You’ll know when your battery is bad. As it gets low you may get strange electrical indications (random warnings and U fault codes). As it gets lower it may drop the memory settings or defaults such as HUD settings. Eventually you’ll get the dreaded chattering relays in the footwell and eventually the lights on the IPC will disappear.

Most batteries can be recharged quite successfully, although AGMs are harder. Start by checking the charge on the battery. Don’t read the DIC when the car is off. The value you see on the DIC is alternator output when the car is running. It will always measure an inaccurately low voltage on the battery when the ignition is off and figures of 11.0V to 11.9V is normal in this case. With the engine on, the voltmeter should show between 13V and 14.5V. You need to measure voltage across the battery terminals using a digital multi meter if possible. A fully charged battery measures 12.7V and a fully discharged battery measures 11.9V. Partially discharged batteries will give a reading somewhere in between.

If the battery is low give it an overnight charge (or put it on a battery tender until you get a fully charged indication) and retest it. A true test is under load and Autozone will do that test for free.
If you have an AGM battery like the Red Top and it has been deeply discharged it's harder to recover it. This might help:
http://www.youtube.com/watch?v=dIoaL3DWWEg

If you’ve recharged it and it still runs down, then you need to start looking for excessive drains. Bill Curlee posted a good method for checking:

http://forums.corvetteforum.com/1567522286-post590.html

There are some common faults which are well known for causing problems:

First to check is the interior lighting rotary switch on the drivers panel. It’s possible for that to be turned on as there’s a setting (fully clockwise) which bypasses the auto off function. Turn it fully counter clockwise and check after about 30 minutes (preferably in the dark) that the interior lights have gone off.

If it’s not the lights something has failed or is badly installed.

Have you fitted an after-market device which draws current? Typically it’s a cellphone charger, radar warner or a similar device that’s the problem.

If still no joy, you need to start pulling fuses to identify the problem.

The power seat switches on the side of both seats are notoriously unreliable. The switch becomes sticky with use and can stick in the “on” position. You shouldn’t damage the motors as they are thermally protected. The fuse may blow so worth checking (Fuse 36 20A in footwell).

The driver’s lumbar motor can also cause issues so check this too (mini fuse 3 15A in footwell). The seat controls connect under the seat. Pull the connector and if the drain stops that’s your problem.

Less common but not unheard of are failures of the headlight motor control module the alternator and the Bose Amplifier under the dash on the driver’s side.

 

hey DeeGee

I'm pretty certain it's not the battery - I've had a new one on it and both are now fully charged and it's still throwing all these No Comms errors

10 - PCM No Comm
28 - TCS No Comms
40 - BCM No Comms
58 - SDM No Comms
60 - IPC No Comms
80 - RADIO No Comms
99 - HUAC No Comms
A0 - LDCM No Comms
A1 - RDCM No Comms

It's going into Ian Goss on Friday - so hope it's nothing major

 

Ah, that's a bit different. I don't think I've ever seen a total loss of comm on the bus. All those modules are separate modules individually powered.

Have you checked the connections at the battery. It looks like a total power failure. You haven't had a battery leak at some stage?

 

From what I understand, the modules are in a loop, so one problem would take them all out.
No battery leak - previous battery was a Gel cell.

From what I've read from various other topics, it either a ground issue or the BCM is screwed. I'll continue checking the grounds tomorrow.

 

I'd be on the grounds as you have total comms failure. Never heard of a BCM & a PCM out at the same time plus door modules et al. The thing that is significant is that they all ground at different points so I'd be back at the battery area.

 

Thanks for the pointer - both batteries are charged to 13v - so should be fine. But who knows at this point.

I think there's a power drain somewhere as well as I've had 2 batteries go flat in under a month !

 

Have you installed any aftermarket items like a security system or stereo amps?

 

Nope - it's a standard car in that respect.
Everything seems to be pointing to an electrical short or an earth issue?

I'm going to check the door accordions and the connectors there - as that seems a common cause for this No Comms issue.