cyberay

I can see the current draw through the rear hatch. When the car is off and all lights turn off and the doors auto lock, the current draw is about 5.1 amps. It decreases in steps over about a 13 minute period to about 0.68 amps, then eventually settles to about 0.5 amps, until something wakes up the car again. I have Max/Min capturing set, so I can see if anything happens after it goes to sleep.

A 0.5 amp parasitic drain would deplete the battery by 12 amp-hours every 24 hour period. This seems high as it would result in a battery too weak to start the car after about 3 days. No?

NSC5

A steady .5 amp draw does sound far too high. I know that some of our members have reported leaving the car for several weeks without a battery tender and having no problem starting so clearly their C7s aren't drawing that amount of current steadily.

A couple of possibilities are:

1. Your meter and/or probe isn't accurate and is giving a false high reading. You can test this by using a fresh D cell battery and a 5 ohm 1% resistor. If the D cell is at 1.5 volts "under load" (measure it, this should be close) then you should have 300 mils of current flow. It is worth a check to make sure you aren't wasting time chasing what seems to be elevated current draw when the real problem is something staying on intermittently.

2. Perhaps the car goes into a deeper sleep mode after 24 hours or so causing current draw to drop into a more normal 100 mil range but unfortunately that isn't something you are likely to find in the manual.

sahlbom

I don't normally use a DC clamp multimeter for low current measurements -- more typically for hundreds of amps. In reviewing the spec's of the smaller 400/40 amp meter (which is the only one I have that will fit in the space), the accuracy leaves much to be desired!

1. The meter has to be rezeroed each time its power is cycled and while held in the same orientation it will be used in. That dropped the 0.5 amps reading to 0.3 amps.

2. In the 40 amp range, the accuracy range of a 0.3 amp measurement is +/- 0.16 amps (or 0.46 - 0.14 amps).

3. The accuracy is further degraded somewhat by not having the conductor in the center of the clamp, due to how the ground wire is routed. Also, a temperature compensation factor has to be applied, since the ambient is below 18 degrees C.

So, measuring the actual sleep current would require putting a precision current shunt in series with the ground cable, which I may do someday, but not for this particular problem.

Of course, I still haven't been able to recreate the PDR not shutting down in simple test cases in just my driveway and garage. We had freezing rain last night, so I didn't venture out into the road salt and sand today for longer tests.

I would like to nail down how to recreate the problem if possible before taking it to the dealer, but that will have to wait until the weekend. Since only one other owner has reported the problem on the forum, I assume it probably isn't a significant design issue. I may just live with it until my schedule frees up in a few months.

NSC5

Good luck and I hope you are able to run down the problem since it could be very frustrating hoping a dealer can run down a rare intermittent.

As you noted accurately measuring very low current is a bit complex. Either voltage drop measurement across a precision shunt or a dedicated Hall effect device designed for low current measurement is needed for accuracy at these levels. Like measuring resistance in the milliohm range measurement techniques are different.

If you are able to recreate the PDR staying on try to see if any other systems are also remaining active which may help locate the root cause. I hate intermittent problems and a couple of years ago I went through a frustrating experience with my 2006 GMC Sierra diesel where on rare occasion the CEL light would be on before I even put the key in the ignition and it would start and run normally but wouldn't shut off without pulling the ECM fuse. The only stored DTC was loss of communications with the TCM (transmission control). After spending some time with the service manual and making numerous measurements I found that at some point a mouse had urinated in the underhood fuse center and this caused some corrosion and a conductive path between switched and constant 12 volt buses and ONLY when the humidity was high was the leakage sufficient to keep the ECM active when its normal 12 volt feed was shut down. After hours of running down the problem replacement of the fuse center took less than 20 minutes at a cost of $150, I hate to think what the dealer charge for this process would have been.

Chevy Cust Svc

Hi sahlbom,

We wanted to let you know that our internal resources are aware of your concern, and would like to discuss it further with you. We've tried to PM, but were unable to do so. Would you mind emailing us at socialmedia@gm.com with "ATTN: Marissa" in the subject line?

Marissa
Chevrolet Customer Care

sahlbom

I've spent the past 4 weeks trying to recreate the problem again, with only one case where the PDR continued to record after the engine was turned off. I check the PDR status about 15 minutes after the car is turned off to make sure the battery isn't run down again.

When the problem first occurred there were about 8 instances in less than 3 weeks.

I talked to a very helpful person at Cosworth, trying to resolve a problem registering on their web site to download the Toolbox. He said there had been a similar issue early in development, but verified that I had the latest software version that should have fixed the problem.

I'll wait until it gets worse before I take it in for service to have a look at it. Although the past two days I've had two other strange glitches in the DIC and touchscreen displays, so that may be sooner rather than later.....

If anyone else notices their PDR recording more than a minute after the engine shuts down, please post any details on the forum. So far, only one other owner has reported it and he is just making sure the recording mode is off before shutting it down.

wingerr

It sounds like you're using an analog ammeter for the measurements- you might want to pick up one of the $2.99 or free-with-coupon digital multimeters from Harbor Freight to conduct your measurements.

To do this, if you have the car inside and can leave your hatch ajar, lock the hatch lock without shutting the hatch, and allow it to sit for a while to let the ECM go to sleep for an accurate measurement.

Pull up the cover for access to the battery, and loosen the negative battery terminal bolt without removing the terminal from the post.
With the ammeter in current measurement mode, place the negative probe on the center of the battery post, and the positive probe tip on the terminal, then carefully lift up the terminal off the battery post. It's important you maintain contact at all times during this action, because if you slip off, the power cycling will waken the ECM and start drawing current from the active systems again. Then you'll have to let it sit for a while again to let it go back to sleep.

If you did it properly, the meter should now be reading the parasitic draw, and you should have resolution to fractions of a milliamp if you need it.
I'd start with the meter in the 10A mode first just in case you have a large draw exceeding 200mA, so it won't blow the meter fuse. If that shows less than 0.2A, then you can switch down the ranges to get a more accurate reading. The reading will normally fluctuate because of the flashing security LED indicator, and the DMM read rate isn't fast enough to show it, but it should generally read below about a 20mA limit.

You can't normally make measurements with the hatch open because that switches the interior lights on causing a large draw, so that's why you need to latch the lock without closing the hatch. It's easily done with a small strip cut from an old credit card, pushing down two clicks one to close the mechanical latch, and the second for the electrical switch. Just don't forget to release the latch before trying to close the hatch!

This shows the placement of the strip to lock the latch:

EcoBrick Bob

Yesterday, I finished installing FatMat Rattle Trap and Mega Mat. The 2 layers took about 8 hrs over 2 days. The doors and hatch were open much of the time. When I went to start the car an hour later, it went click... click...click. The lights went on etc. as it was in our garage. We were heading out to a movie and dinner, so we took our G8 instead. When we came back, the car doors wouldn't open, and I had to use the key to open the hatch. I immediately hooked up a charger and the battery started taking the full 10 AMPS. Opening the door, the clock said 12... It took over 1/2 hr for the charge to be enough to start the car. I ran it for a few minutes and turned the lights off manually on the left stalk. When I shut it off, the charger was still reading over 80%. Same reading 3 hrs later when I went to bed. This AM it was completely charged. Car only has 700 mi on it.

I do have PDR but it wasn't on. Only the interior lights were lit. Thought they were supposed to shut off after 15 minutes as a safety preventative measure to save the battery. Guess NOT!

Noticed the C7 battery is not a very high amp rating. That concerns me as my Twin Turbo Flex came with a much better & higher AMP battery, that only lasted 3 1/2 years. My last Vette (new C5) had a battery that instantly quit one day at about 3 years and 10K miles. Worked fine when I started. Drive 80 mi to my son's, and 10 minutes later, it wouldn't re-start. He said battery, I said something else... He was right. New $65.00 battery lasted the next 5 years with no issues.