On my 98 Tahoe if I don't start it in three or four days the battery is dead. I've tested the battery after charging it and it's in great shape. I've had the starter and alternator tested and some parts replaced and they both work as they should. I've done the parasitic draw test with the DVM and it shows no draw. I've tested each fuse as well while the negative battery was disconnected and the Wiper and Radio fuse showed power. I tested a 98 and 99 gmc truck the same way and they too showed power at these two circuits so I figured that was normal. Is there anything else I could do to find out why my battery dies? I've also swapped out the battery with two other ones and the same thing happens. Thanks
parasitic drain got me stumped
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HiHoeSilver
Away!
I had this on my OBS. Turned out to be broken hinges on the vanity mirrors, so the switch stayed open and the lights were always on.
Danny3737
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It's possible you have a cell dying even though it test ok. You could try unhooking the battery for three or 4 days then hook it back up and see if it starts. If it starts, you have a drain. If it doesn't, then it's the battery.
PatDTN
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Do you have a gps plugged in that stays on? How about a USB charger adapter? Those draw a surprising amount of power even with nothing plugged in. Of course interior lights is bad but that's obvious. Radar detectors draw power. Dunno, just tossing out ideas.
iamdub
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Something's pulling power. The DVOM test is the best way to track it down, but you said yours showed no power. Either the power draw is too small to register on your DVOM or that function of your DVOM is faulty.
PatDTN
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Add a thought about aftermarket alarm systems.
No alarm, no gps, no usb charger. I've pulled out the entire interior now. The previous owners had a monster sound system installed and I wanted to pull out all the remaining miles and miles of extra wiring. I've tried letting the truck sit with no fuse in for the stereo and it still drains the battery. I'm going to give up soon and take it to a shop. Thanks for all the ideas
I finally realized my DVOM had a blown fuse and that is why I wasn't showing any parasitic drain! Doh!! I got a new one and retested the truck. It shows 0.168 amps. I uplugged the fuses one by one and the only one that made this value drop was the 20A ECM-B. No other fuses under the hood or in the truck made this amperage go away. I also disconnected the starter and alternator before doing this test. Is this normal or does this mean I have a short in the fuse bundle?
iamdub
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That draw isn't "high", but on the threshold of unacceptable for a daily-driven vehicle. This is why it's dead after a few days of sitting, as you've experienced. I'm not sure what all is controlled by the ECM-B fuse, but I know a few sensors are and I think the fuel pump relay is. Your best bet is to find a schematic for the circuits involved with the ECM-B- what sensors, relays, etc. are connected to it. Disconnect them one at a time while someone watches the DVOM to see when the current draw drops. I'd aim for oil pressure sensor and O2 sensors. Did this problem start after some mechanical work was done?
