don pablo

UPDATE: I thought I had updated this post in January with the resolution of my problem; apparently not. The problem was the battery. I failed to notice when I bought the replacement Duralast battery in September 2015 that it was approximately a year old at that time. I think there must have been a problem with a cell due to sitting on the shelf for so long. I replaced it with OEM ACDelco and had no further issues. I sold the car in late May 2016.


Please pardon the long post. I have a 2008 Z51 M6 coupe with 58,8xx miles. I drive it several days each week, depending on weather. I drove it several days in a row before yesterday. I went to the garage yesterday am to put something in the car and I couldn’t open the doors. I grabbed the second fob and couldn’t open the doors with that one either. I put a new battery in one fob and still couldn’t open the doors. I could use the fob to open rear hatch, use lock/unlock to make the lights flash and turn the alarm on/off.
I used the manual door opener under the hatch to gain access. I tried to start the car and got immediate messages to “Service Antilock Brakes” and “Service Car Soon” but it wouldn’t crank or start. I put the fob with new battery in the glovebox slot and it still would not crank or start. Same result with the second fob. I did on one try get the “welcome” message and the DIC did show the name of the fob I was using. But when I pushed the bottom of the start button to take it out of accessory mode, I got the no fob detected message.
I had a similar problem with doors not opening and no fob detected in September 2015 (https://www.corvetteforum.com/forums...this-fast.html). The battery at that time read 4.8 volts (it was a four year old AC Delco). I replaced the battery at that time with a new Duralast Gold 85DLG, which appeared to solve the problem. Yesterday the battery was reading a little over 12. Hard to tell precisely with the vintage voltmeter I was using. I cleaned the terminals and made sure both were securely fastened. It still would not start.
The battery this morning was reading 9.0 volts. I took the battery to AutoZone to test. They hooked it to a charger for a few hours and told me the battery was fine. . It was reading about 13.5 when I picked it up. AutoZone suggested that there might be an excessive draw on battery while the car was turned off.
I rested the battery in the car and connected the positive terminal. I used a Klein digital multitester connected in series with the negative cable to check for any draw. On the 10 amp circuit it never changed from zero. On the milliamp test if did not show above 18 milliamps.
I reconnected the negative cable and was able to start the car. The DIC and the voltmeter gauge showed registered 14.5. at about 1200 rpm. I have it connected to a battery tender tonight.
Is there anything else I can check? I’m leery of getting stranded at this point. Does the DIC showing 14.5 volts mean that the alternator is working properly? Is the culprit most likely the battery regardless of what AutoZone says? I would appreciate all suggestions on what I need to do to avoid this situation again. Thanks.

1968swbbigblock

I would check the cable connections down at the starter.
Overtime the wires become brittle & or loose from sitting so close to the exhaust manifold.
Confirm that your ground to the frame from the battery is also secure and clean.

4SUMERZ

If your voltage is 14.5, then the charging system is OK.
You might just have a parasitic draw. There are things that you can check, if you have a good digital voltmeter set at milliamps.
Normal Parasitic draw for most newer vehicles is usually between 40 ma - 50 ma
Ideally, less than 18ma (11-17ma) would be about the best a C6 will do after about 15 minutes of shutting off the car. There are modules that turn off by timers if lights are left on, etc.
Hope this gives you some starting point.

Dano523

Also, if you have Onstar in the car, and even XM, but do not use the services, think about disconnecting them.

Hence with not having a On star service, the module is still phoning home from time to time, and what may be draining the battery when it can not get a signal and keeps trying to connect.

john05vette

800 CCA with 120 reserve is what you need....

john05vette

I put an AC Delco size 78 dual terminal battery in my 05 base Conv. Vette......800 CCA...GM and Chevy book calls for an AC Delco 86 G heavy duty with 650 CCA....This would not work well for my car....The size 78 fits in my car and gives 800 CCA with 120 reserve.....But be aware that amny of us are having problems even after making sure that the battery is good....Computer issue is most likely the reason. Although some insist on starter or/ and solenoid.....or grounding issues....or battery cable issues.....It's the C6 ones that are mostly affected.