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2008 Sonata, 3.3/Auto, 110k miles, frozen/snowy Northern NY...

My Aunt's car has begun acting belligerent electronics-wise. Was surging/chugging on her and would stall and not turn over, I was thinking it was the alternator. "Upon further review" it will run fine sometimes (earlier today I had it idling fine for 45 minutes in the driveway while I de-iced it), other times will surge and buck; if left parked and running the battery light will come on and after a minute will either stall and not restart, or will not respond the throttle input - floor it and it doesn't affect it, maintains it's ~800 rpm idle. Shut it off and it will not turn over, acts completely dead. Or it will start right up... (?)
It was showing codes of P0562 (System Voltage Low) and P0708 (Transmission Range Switch Short Circuit).
Looking for ideas, please (?)
 

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How old is the battery? I would probably start by checking out all the main electrical connections and chassis grounds. Then get the battery and alternator load tested.
 

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Never assume a battery is "good" just because of the date.. I've seen Brand new batteries failed when just installed. Get it load tested...
 

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You could have a bad alternator or some loose connections, do the symptoms have anything to do with the temperature outside? I'm not sure where you are from, but a lot of members here have been posting about electrical related issues lately because of all these cold snaps everywhere. based on the fact that you spent 45 minutes just de-icing your car makes me ask the question.

If you can still start your car fine then there's really no need to test the battery, but it wouldn't hurt. Just don't replace it (I see a lot of people in the forum try that as a first step and it never resolves the issue).
 

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2008 Sonata, 3.3/Auto, 110k miles, frozen/snowy Northern NY...
Hello neighbor.

My Aunt's car has begun acting belligerent electronics-wise.
Cars are not belligerent. However their owners sometimes feel the cars are like that.

It was showing codes of P0562 (System Voltage Low) and P0708 (Transmission Range Switch Short Circuit).
Looking for ideas, please (?)
System low voltage sounds like terminals and grounding points need cleaning
Yeah, corrosion on a 2008 vehicle sounds about right to bring all this weird electronic stuff.
Check and clean the terminals of the battery and alternator and starter
Check also grounding strap of the battery, and engine block

Transmission range switch short circuit sounds like a goo reason why it won't start.
Vehicle can't tell if it is in park or neutral

So looks like more than one issue here
 

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Discussion Starter #8
(Hi 'avisitor' - Massena here, aka "South Canada")
The terminals all look good, still cleaned what I could get at.
Hooked a trickle charger on it all day, and it started fine both before and after, but I didn't let it run that long.
And I agree with the possibility of multiple issues, but if the battery is charged it starts fine. (It's also has a bad brake line that needs fixed so I can't road test it. One crisis at a time.)

HOWEVER part of my question remains unanswered: Why would the throttle input be completely unresponsive when the battery is weak? Are these cars prone to that in a low voltage situation?

Or is there a possibility it's got moisture where it shouldn't?
I'm a 10-year MINI Cooper owner, I know our cars are susceptible to acting very wonkie (technical term) with both those situations, but even in "limp mode" the throttle will respond at least a bit - this Sonata doesn't change a single rpm.
It's also crossed my mind that, while we had a "January thaw" last week (hit 50 for a couple days), she may have hit a few puddles bigger than she thought and then with the next cold snap a couple days later (below zero) something's literally frozen? She says no, but....
 

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Sounds more like the TPS (throttle position sensor) is bad. It will make your car buck, backfire and just run awful.
 

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Need 10.5V minimum to power up PCM and run misc engine control

With engine at idle, DVOM across battery posts...

Move red lead to alternator stud...

Put red back to battery...

Move black to engine metal..

Voltage measure better be within 0.3V all way around

Ground lug off Negative cable to fender,, remove offending paint

Ground strap at left frame rail,, remove offending paint

Positive battery cable for first 2yr V6 has cable fault... high resistance in cable drops charge voltage,, find 14.x at alternator stud,, and less at battery posts
 

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Finally brought it to some "pros":
Battery is fine, Alternator was shot.
Reman installed and even the CEL is out (so far).
Thanks for the input guys.
I'm sure I'll be back.
Thanks for the update.
Appreciate it when there is news of a fix

Hope it stays working
Good luck
 
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