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I tried searching about this but did not find anything relevant. Creating the thread for research and future reference.
Short story: Wife drove the truck to the store (less than a mile from home). Said (red) battery light came on on the dash, and shortly after, ABS light. After the store she could not start the car (would not crank). Left the truck on the parking lot and walked home. After work I took the battery/starter and drove over to the store's parking lot. Hooked up the battery booster and started right up. While driving home, abs, esp, srs light were on and off. Water temp light came on, cruise control not working. Seemed like truck was driving in a low range gears mode. Radar detector displayed "low vot". It did that on a different vehicle when battery was low/dead.
Troubleshooting: Checked the alternator belt, its still there, so the alternator is spinning. Charged the battery on "fast" mode for couple of hours. Started the vehicle without any issues. After a few minutes of idling, battery light came on again. Shut it down and it did not start again without a battery booster. Checked the battery voltage, it was below 11v. Checked the voltage with engine running, same 11v. Bad alternator? At this point, charging a battery to a full charge on "slow" charge. So far it was charging for 8 hours or so. Usually my other batteries would be fully charged by this time. Bad alternator and bad battery?
could you be more specific on how to get to that menu?
dash screen on mileage (turn truck on to click through to display mileage)
turn off truck
key on position 2 (do not start truck)
press "r" button on dash three times
voltage will be displayed
When you push the 'R' button you may have to experiment with how fast you push. The first few time I did it (to get to the menu to tell the computer I had changer the oil) I pushed too slow -- it didn't respond. My guess is about 3 times in 2 seconds works.
OR - if you have a voltmeter, hook it up to the jumper terminals under the hood, start the car and read the voltage. It should read about 14V on a fully charged battery, less if the battery is down. If the alternator isn't putting out, voltage of 11 or less in not unheard of. If it gets below 10.5V the computer refuses to operate and you will probably lose all data saved in the NAV system.
Took the alternator to the alternator rebuild shop to do the test. They put it on the alternator dyno machine and told me that as soon as they give it some load, "it drops". I'm still not exactly sure if voltage drops or what, but technician will take a look at it to tell me what exactly wrong with it.
I did not buy a new one. Mine was rebuilt with new parts. But I think new one is ~$400 My alternator is located on the passenger side, towards the bottom of the engine. Removing it was not too difficult, putting it back was little harder. Alternator is not light weight and there isn't much room to work. My right hand was all scratched up. Looked like I was depressed and cutting myself lol. If I'd have to do it all over again, removal and installation would take me about 1 hour. Because you also need to remove some intercooler houses and serpentine belt. I also replaced that belt with a new one. I hope this helps.
Reviving an old thread. While in stop-and-go traffic this morning on slippery roads (with ABS engaging several times), the red battery light came on. I'll go ahead and try the suggestions mentioned above.
I'm not sure if it's related, but 2 days ago, the "ESP Inoperative" message came on randomly. It has since turned off after shutting down the car for a couple hours and restarting again.
Voltage after starting.
I used the engineering menu to determine battery voltages after a couple hours. The red light seems to be gone for now, thankfully. Perhaps it was the ABS constantly turning on/off this morning due to slippery conditions.
Voltage before starting.
Last edited by Isentropic; Jan 9, 2018 at 03:10 PM.
I went off-roading couple weeks ago, and the red battery light came on again. Not sure what's going on.
Recently, the "Gas Cap Open" message also appears. Could they all be related? Perhaps a faulty alternator/battery causing electrical glitches?
Check engine light is also on.
I wouldn't think the emissions is related to a battery or alternator. But, is your gas cap actually open? If not, probably just time to replace it.
You never mentioned what your battery voltage was after the car sat for a few hours and also while running? Note whether the battery light is illuminated during this. Or, just use a DVM.
Just a guess, but the first thing I think of is a loose/dirty connection somewhere amongst the alternator/battery system, since it seems to be happening intermittingly - or at least that's a good place to start since it's a "freebie" fix if it's the issue... and always a good place to start with electrical gremlins.
Thanks much for the insights. I’ve been checking the battery voltage for the past two days, and it seems to be hovering around 11.6 V and 11.7 V when the car is not running. Once the vehicle is started up, the voltage jumps to around 13.7 V. Does this seem normal? Thanks so much again.
A good battery will show mid to upper 12-volt range. 11.7 is too low. 13.7 when running means the alternator is good... assuming you've checked the battery/alternator cables. It's possible to show 13.7V, but not be passing enough amps.
With the new "data", though, signs point to a bad battery (again, on the "assumption" from above). How old is the battery? The intermittent thing could be explained by the battery being on the fringe and the alternator not always able to keep up. It will get worse - fix it before you get stranded.
A good battery will show mid to upper 12-volt range. 11.7 is too low. 13.7 when running means the alternator is good... assuming you've checked the battery/alternator cables. It's possible to show 13.7V, but not be passing enough amps.
With the new "data", though, signs point to a bad battery (again, on the "assumption" from above). How old is the battery? The intermittent thing could be explained by the battery being on the fringe and the alternator not always able to keep up. It will get worse - fix it before you get stranded.
Thanks much for the suggestion. A VERY SCARY thing happened today:
I was driving on the freeway and suddenly the entire car just shut-off and turned back on, all in one sec. I heard a thump too.
I was very startled, especially at such a high speed. Since I have KEYLESS GO, I don't think it's due to the physical key losing contact with the ignition (since it's obviously not even plugged in). Could it be due to the dying battery? Has this situation happened to anyone?
Just bought a replacement battery on Advance Auto Parts (AGM type), and will see if I can change it myself.
Thanks much again.
Last edited by Isentropic; Apr 18, 2018 at 09:39 PM.
Thanks much for the suggestion. A VERY SCARY thing happened today:
I was driving on the freeway and suddenly the entire car just shut-off and turned back on, all in one sec. I heard a thump too.
I was very startled, especially at such a high speed. Since I have KEYLESS GO, I don't think it's due to the physical key losing contact with the ignition (since it's obviously not even plugged in). Could it be due to the dying battery? Has this situation happened to anyone?
Just bought a replacement battery on Advance Auto Parts (AGM type), and will see if I can change it myself.
Thanks much again.
This has happened to me a couple of times. Just the computer suddenly goes and then reboots. I didn't hear a thump, but when the alternator/battery started really tanking, I would find the abs light would come on, then the brake light, then it would stop shifting and just go into neutral, usually in the span of a minute or two. So, the thump might have been it suddenly downshifting or throwing the brake on for a second. When I first got it and had starting issues, I had it checked a couple times and was always told that the battery and alternator were fine, until this last great adventure. One thing I did notice is that with the oil filler right above the alternator and pulley, when I was investigating this there was a lot of oil on the stuff below and around the filler cup. I think it's possible that the oil might have had the belt slipping a lot and may have even gummed up the pulley enough to eventually kill it. But, just a thought. After reading so much about this issue, I've come to think there are some serious problems with this electrical systems of these GLs, but a new belt, new alternator, and new battery and, fingers crossed, mine's better. But, given how incredibly dangerous this issue with our cars is starting to seem, I'm wondering if MB has any ideas about making it better permanently. I myself am a little nervous about driving my car anywhere off the beaten track, even with new alt, bat, and belt and wonder that I might not be a deadly road hazard if it could suddenly go again and I just lose everything on a dark freeway at 80mph. Eeeek.
Thanks much for the suggestion. A VERY SCARY thing happened today:
I was driving on the freeway and suddenly the entire car just shut-off and turned back on, all in one sec. I heard a thump too.
I was very startled, especially at such a high speed. Since I have KEYLESS GO, I don't think it's due to the physical key losing contact with the ignition (since it's obviously not even plugged in). Could it be due to the dying battery? Has this situation happened to anyone?
Just bought a replacement battery on Advance Auto Parts (AGM type), and will see if I can change it myself.
Thanks much again.
I haven't had it happen at speed, but it is possible for your Keyless Go to lose "touch" with the Key. Usually there's a Key Not Detected message on the dash, and I've had it shut the car off while parked when it happens. Pretty sure my battery in the fob is getting weak and could use replacing, but I don't know if there's a more in-depth reason for it. And It's never happened to me while at speed, so I'm not sure if that would've been what happened. The hardest part of your battery change, is physically lifting the old out and getting the new in. They aren't the lightest things.
The battery is a vicious beast. I used a heavy pry bar with a curved end. I pry the battery up enough to get a long, flat, sturdy bar wedged just a millimeter under the bottom and then yank it up, sliding it up the bar (I actually used a piece of oak 1x2 with a wedged end) and out. Not 5 seconds out, but you can get it out if you can just get something under it.
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