This one has me stumped

I have 1999 Malibue with the 2.4L I4 engine. It has 160,000 miles on it and I absolutely love the car.

Last night as I was driving home the ABS light lit on the instrument panel. The car drove fine the rest of the way home. This morning, I got in to take the kids to school and the ABS light lit up once again after I'd been driving for a little while. At this point, I was thinking it was probably the ABS module or a sensor that needed to be replaced (and, honestly, I wasn't too worried about it b/c cars drove fine without ABS for years before it was added).

Here's where things got weird. As I drove, other things started happening as well. After the light had been on a bit I noticed that every time I hit the brakes, the radio would turn off and then it would come back on when I let off the brakes (just like I had taken the battery cable off...it was completely reset). This went on for a few minutes and then the transmission got to where it was shifting VERY hard and seemed to not be able to make up its mind about which gear it should be in. After dropping the kids off, I stopped in a parking lot to see if I could figure out what it could possibly be. I read in the manual that to reset the ABS system you could turn off the key and back on and it would reset. So...I turned off the car and, wouldn't you know it, it would not start back up. The battery was completely drained. I got a jump and the car was back to running. I took it home and let it set idling for a bit and when I came back to shut it off the check engine light was on, along with the ABS light.

It appears to me that there is a dead short somewhere in that braking system as it completely drains the battery whenever I hit the brakes. I may be wrong and am looking for ANY input as to what could be going on.

Any comments are appreciated if they'll help me figure this one out. Anyone else had anything similar to this happen? Any thoughts?

Thanks

One more thing...I did notice last night when the light first came on that the lights appeared to be dimming the longer I drove.

Here's a completely off the wall question...could a bad alternator cause these kinds of issues? I've had my suspicions about the alternator for a while now as it's been making some squeaking noises for over a year...

How old is your battery?

Has the battery been checked out? Load tested? Has the car been checked for a parasitic draw?

Has the alternator been tested under a load?

Most auto stores will test your vehicle for free....

Do you have a voltage gauge in your dash?

If yes, what is the voltage with the key on? What is the voltage when you turn the key to the crank position? A car's computer will not function if the voltage is below 9.7 volts....

It does sound like a bad battery....the car starts and runs with a jump.....I don't think there is anything wrong with your ABS system, other than the fact that the low voltage is triggering the light....

A bad battery can take out an alternator by making it work too hard.......alternators are not chargers.....they provide power for the car once it is started, and they will recharge just the energy lost by the initial start of the car......however, if the internal "resistance" of the battery is increasing, the output of the battery decreases......

So, you could have two problems....a battery and an alternator....have both checked by Pro, unless you know how to check it yourself....

Thanks for the response.

The battery is only about 8 months old. About a year ago, I started having problems with the car being slow to crank. It acted like the battery was weak. I didn't want to replace the battery until it actually went dead so I drove it like that for about 3 months until it got to the point that the battery was so weak it wouldn't turn the engine over. I suspected the alternator then because the battery didn't just die (like mine usually have)...it just seemed like it never had a full charge until it eventually got too weak to do it's job. During that time period, I would have all kinds of weird electrical issues with the car. The ABS light came on then intermittently as well as the check engine light when the battery got really low. I replaced it with a really nice battery and everything seemed fine...until now, 8 months later.

It's really got me thinking that it's either the alternator not doing a good job of charging the system OR there's a power draw somewhere. I just remembered that I do have a battery tester that also tests the alternator output...I'll put that on the system this afternoon and post the results.

One thing that's got me pretty sure it's NOT the battery is that before I got the jump this morning, when I let the car sit for 5 minutes or so, the battery was noticeably stronger (just not enough to crank the car). That leads me to believe that the battery was trying to charge back to it's minimum baseline while the car wasn't running.

If an alternator goes bad, can it cause a drain on the system itself?

Yes it can.....one thing you should try is a parasitic draw test........

Yes it can.....one thing you should try is a parasitic draw test........

How do I do that?

By the way, I have had the battery on a charger for a few days. I have noticed that the charger comes on every now and then to "top off" the battery. Does that mean something is drawing it down?

To do a parasitic draw, you make sure everything is off, and no key in the ignition.....disconnect the negative battery terminal, and attach a jumper wire between the neg battery terminal(I usually install a bolt into the side post to clip onto) and the neg cable.......then attach either an ammeter(10A scale) or test light between the neg battery terminal and the neg cable......after about 5 minutes, remove the jumper wire and any current flowing will go through the test light or the ammeter.......if the light is out, then there is no draw......if it is lit, there is......if using the ammeter, the draw should be less than 50 ma, or 0.050 amps.......if higher, there is a draw......

If you want to know if your alternator is causing the draw, disconnect the alternator completely(electrically)......careful, the large red wire is "hot".....if the light goes out or drops below 50 ma, the alternator is the draw.......if it doesn't, then you have to remove fuses one at a time, to see if there is a drop in current flow, to find the circuit that is at fault.........

wow - please report your findings. This sounds like a crazy problem. The closest I've come to that scenario was a rusted ABS cable in the front right well that rotted and sent the ABS signal off.