OT: BMW X5 - Just a bad battery?

[trader_4]

So, the X5 started acting up a couple months ago. It had the check engine light on. I have the dealer computer software on a PC, so I read out the codes. It was complaining about missing signal from intake camshaft sensor. I reset it. A couple weeks later, it complained again, this time the exhaust side. That's weird, unlikely that there is a problem with both sensors/circuit. Cleared it and no more issues for a couple months.

Then the brake light came on. Not the ABS, but the warning for the brake system, which IDK what all will cause that, but presumably low brake fluid would. I could see that there was BF there, but it might be near the low limit. Before I could get some BF, I drove it for another couple days and then it put up the "check brake linings" mesg. Now that's weird too, because as I recall the brake linings wearing out only trigger that mesg, not the red brake light. And when it first put up the red brake light, it didn't have the check linings mesg up until many drive cycles, few days later.

So, I added some more fluid to bring it up near mid-point. Took a day or two, but then the brake light went out and no more check brake linings. OK, that seems good.

About a week goes by, I notice while backing up, that the car seems to be hesitating, like it's losing power. A few days later, Check engine light again. This time it's complaining about intake camshaft sensor and running lean with a problem with both upstream O2 sensors. So, now my suspicion shifts too maybe this is a bad battery. These X5 are known to be sensitive to electrical troubles. So, I measure the battery voltage. This is after I had the car sitting there, ignition on, while running the computer diagnostics for maybe 15 mins. Sure enough, the battery reads only 11.9 volts! I started it up, it reads

13.8v, so the alternator is OK. The starting thing is one of the weird things, through all of this, the car has started up just fine, spins right over. OK, so it's running, I decide to take it for a short run. It stalled on me about 5 times, just going around the block.

I charged the battery for about 8 hours, starting at 10A. Last night it was at 12.6, but I figured that would not last. By AM it was 12.3. Not good, it's clearly bad. (I also checked the current draw when the car is just sitting there. It's 90ma. I think the spec is 45ma, but it's been about 75ma before and that clearly isn't a real problem. The battery is probably 5+ years old too, so it's due. What I find amazing is:

1 - The car shows 13.8v at idle, but stalls out on the road. Every other vehicle I've seen, even if it's a completely dead battery, once you jump start it, they keep going.

2 - Going around the block, while it stalled about 5 times, each time it spins right over, starts right back up. I would have thought that after a few of those, if the battery is that bad, then it would either not turn over or show some struggling while cranking, but none of that.

One thing that also point to the battery as the culprit is that it only stalls when slowing down, eg at a stop sign or to make a turn. So, the alternator output would drop.

Good news is PEP Boys has a Black Friday super deal going on. I can get a Bosch replacement at 35% off, only $104. That's a great price, it;s a monster battery, G49/H8. So, I'm going to get one, no question it's bad, but I'm still amazed at the symptoms, if that's all that is. Also, it's stunning that with all the computers in this thing, it can't give a warning that the battery is going bad. Like if the car sits overnight and it sees the voltage is only 12.3 next morning, you'd think it would set a code and the CEL to warn you that either the battery is bad or you have a parasitic load, etc. I guess it should see that X times over some period, just like everything else, before it warns. But there is no warning, they just wait until you're stuck.

Any thoughts on the symptoms and it just being the battery? Anyone see this kind of thing before?

[Ed Pawlowski]

I'm active on the Genesis forum. It seems that unlike days of old, when the battery is near EOL, funky things can happen.

Remember when the car didn't start you jumped it and bought a replacement for the 4 year old battery? Then life was good again. With all the computers in cars now. it seems a lot of things start getting ragged even though you had enough power to start. People have complained about poor running, poor shifting, rough idle.

One guy was away for a week and the battery went dead. Car was in the garage, locked. He bought the car used and never knew that the mechanical key in his fob was not cut. He had no way to get into the car, no way to pop the hood to jump it or open the trunk to get to the battery.

Technology is wonderful. When it works.

[mkolber1]

a bad ground someplace? m

[trader_4]

Well, as Popeye would say, "shiver me timbers". I was about to take the battery instead, I decided to try running it one more time with the battery freshly charges, as much as possible that is. It ran worse that ever barely idling, very rough at mid-speed just sitting there. The dash displayed engine failsafe, then died. So, I started thinking this is more than the battery, maybe a bad fuel pump. I decided to hook up the computer again, to see if there were any hints from new codes. When I went to hook up the charger again, I happened to glance at the area where the air filter and MAF are. Low and behold, a joint on the intake plumbing, right after the MAF had come apart and was wide open! When it threw the lean codes, I did look at this 90 deg big bellows thing they have. Those crack and cause leaks. I should have looked at the whole intake path. This is about a 4" diameter rubber like material pipe thing that goes over the plastic housing for the MAF. Held together by a hose clamp. I guess it just wasn't tight enough and came loose. So, the MAF didn't see air moving and the whole shebang just goes whacko. Drives fine again now, with the 1/2 bad battery.

I'd bet if I hook the computer up to it now, it still wouldn't have something that says "MAF - implausible, check". Implausible is one of the words BMW likes with their codes. I'd bet it would still say lean, O2 this, misfire that. So, I'll get a new battery and the only remaining mystery is what's causing the occasional intake and exhaust cam shaft sensor signals missing. But when I read the computer, it had one occurrence of that and it's been a month since I reset it, so we'll see.