Help me understand OBDII scanner

A

Alex_V

Dump the diesel
My 2019 F150 was acting up like battery is going dead, hard to start. Until yesterday when it didn't start, not enough juice to crank the starter.

Took the battery to Autozone, they tested it and said it was fully charged and appeared to be good. I bought a new battery anyways, and sure enough truck started up.

Drove 300 miles, and next day battery is feeling weak. So I plugged in a OBDII scanner and while running it was showing 14 volts, but it gave me an upper and lower volts. I assume that is what the photo shows.

My assumption is that alternator is overcharging the battery and thus killing it. Am I correct?
 

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Look at the numbers next to the voltage graph - high of 17.413, low 10.531. Are those the high and low spikes? Which may cause the issue. Called Harbor Freight support, they couldn't tell me what those numbers were, but at least tech support spoke english. That I was impressed with.
 
you didnt disconnect the BMS by chance to defeat the Auto/Start/Stop?
If you need to replace the battery go up a size to H7. The 150s usually come with H6 sized units
 
Alex_V said:
Look at the numbers next to the voltage graph - high of 17.413, low 10.531. Are those the high and low spikes? Which may cause the issue. Called Harbor Freight support, they couldn't tell me what those numbers were, but at least tech support spoke english. That I was impressed with.
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That's just the range of the graph, not the high and low voltages measured by PCM.
 
Last battery lived for about a year.

I did disable Auto Start many moons ago. Never messed with any BMS stuff. No stored codes, just something acting up funny.
 
The truck is smater than you. If you don’t have a pending or permanent code, it’s operating within design parameters.

“Inherited” my old man’s 2012 GMC and drove it back to Minneshitholia. Noticed the voltage gauge was showing about 12v while running, so I stopped and grabbed an alternator JIC I had to perform an emergency alternectomy on the highway.

Get home and start snooping, the ECM in this thing modulates alternator output based on load.

Never threw a code, so back to NAPA the hitchhiker went.
 
Demand based charging systems are the norm now as it is part of how they achieve some of the mileage numbers.
 
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Very rarely and randomly I saw "Check charging system" warning on dash, it was usually after truck won't start, but next turn of a key it will fire up as normal. Super random, weird issue. But I think it is getting more prominent.
 
pickled egg said:
The truck is smarter than you.
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This is a problem that even the best auto techs run into these days.

General wisdom is that the electronic battery testers they use at auto parts stores aren't infallible. If replacing the battery fixed your issue, it may well have been a weak battery that the tester wasn't failing for some reason.
 
I'd start with the simple stuff. Test the relay for the starter. Looks for green crusties depending on where it lives. Physical connections at the starter. Then move on to voltage drop testing.

Beyond that you are into wiring diagrams, graphing scopes and lots of testing.
 
Gauge was showing ~15V while I was writing that prior post while I was fueling up. Here’s where she sits now rolling down the road.
 

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pickled egg said:
Gauge was showing ~15V while I was writing that prior post while I was fueling up. Here’s where she sits now rolling down the road.
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Does it ever show the signs of not starting when you are running around during the day or after it sits a day or so? Could be a faulty module not shutting down for some reason and pulling too much amperage draw while sitting. Energy vampires are fun to diag on newer junk.
 
Venom51 said:
Does it ever show the signs of not starting when you are running around during the day or after it sits a day or so? Could be a faulty module not shutting down for some reason and pulling too much amperage draw while sitting. Energy vampires are fun to diag on newer junk.
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Oh don’t I know that!

Seen more than one GM with a “phantom draw” after the BCM goes to sleep.

Every time, it’s been the damn SpyStar module.

No issues on this pig, other than the lack of structural integrity due to destructive oxidation of ferrous metals that prevents it from obtaining state consent to traverse the roadways back in the Lobstah State.
 
Alex_V said:
Last battery lived for about a year.
I did disable Auto Start many moons ago. Never messed with any BMS stuff. No stored codes, just something acting up funny.
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How did you disable ASS? A switch?
Do you daily drive the truck?
you have a parasitic draw somewhere if the battery is getting consumed that quickly or you didnt reset the BMS correctly last go round.
 
TurboBlew said:
How did you disable ASS? A switch?
Do you daily drive the truck?
you have a parasitic draw somewhere if the battery is getting consumed that quickly or you didnt reset the BMS correctly last go round.
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I used Ford Scan to disable it. That was about 5 years ago.

Pretty much a daily driver.

Never reset BMS, didn't even know it was a thing.
 
Alex_V said:
I used Ford Scan to disable it. That was about 5 years ago.
Pretty much a daily driver.
Never reset BMS, didn't even know it was a thing.
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Disabling through forscan is exactly what you dont want because it messes with the State of Charge. You have shut the BMS system off. Put the truck cluster in engineering mode... see what the battery voltage is before you start the truck. Then you should see the charge go up to 14.5ish +/- A good battery should read 13 volts. Less than 12.5 volts is when things start acting wonky.
Worst case put the battery on a charger... then reset the BMS so the module sees the battery as new and look up your as built config file to see which setting you changed to disable the BMS.
 
TurboBlew said:
Disabling through forscan is exactly what you dont want because it messes with the State of Charge. You have shut the BMS system off. Put the truck cluster in engineering mode... see what the battery voltage is before you start the truck. Then you should see the charge go up to 14.5ish +/- A good battery should read 13 volts. Less than 12.5 volts is when things start acting wonky.
Worst case put the battery on a charger... then reset the BMS so the module sees the battery as new and look up your as built config file to see which setting you changed to disable the BMS.
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Out of curiosity, why would turning off Auto Start / Stop via software be bad? I did that long time ago and for a few years battery was normal. I never disabled or reset BMS, in fact I didn't even know there was such a thing.

Am I reading your suggestion correct - charge the batter up and reset the BMS (Ignition ON, five times flicker brights, 3 times brakes) and see what happens? I am no longer offended by a statement that that the truck is smarter then I am. lol
 
Google or you tube if you have to, on checking for a parasitic draw on the battery. You’ll need a multimeter and some one to help pull fuses. There is to much to type out how to do it. But a lot of videos explaining how. Simple answer, everything is a computer or they call module that you touch. Radio isn’t a radio it’s a module, heater control= module. So on and so on. If there is a problem with one it may not go to “sleep” draining your battery over night. Video will explain a simple check to narrow it down.
 
assjuice cyrus said:
Google or you tube if you have to, on checking for a parasitic draw on the battery. You’ll need a multimeter and some one to help pull fuses. There is to much to type out how to do it. But a lot of videos explaining how. Simple answer, everything is a computer or they call module that you touch. Radio isn’t a radio it’s a module, heater control= module. So on and so on. If there is a problem with one it may not go to “sleep” draining your battery over night. Video will explain a simple check to narrow it down.
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Your suggestion makes sense, but the problem with drained battery happens after hours of driving, with 14V showing via scanner. Long drive = weak battery while it is showing 14V continuous charge from an alternator.
 
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