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Discussion Starter · #1 · (Edited)
Hi!
I recently installed an ODB2 reader (BT verison that connects to my iPhone) so I can read some interesting parameters while driving (ATF temperature, A/F value etc).
One of the things I have ón display on my screen is battery voltage. But it puzzels me!

When the ignition is on (but engine off) it shows roughly 12V or slightly above (12,2V) even when battery is fully charged. It's an almost new dry cell battery (12 months) which I have properly maintaned by externally charging it a few times.
When I start the engine and transmission is still in P, it increases to 13V+. But when I put the transmission in D, it drops to 11,2V after a few seconds and stays there as long as I drive, with the exception when I release the gas pedal and roll downhill, then it's 13V again.

So it seems something in the transmission is really pulling a lot of voltage from the battery! I know the battery is in almost brand new condition, and it cranks very fast. So basically there can be two possible reasons for this phenomenon.

1, The ODB2 voltage data is not correct, and shows roughly 1 V below actual value.
2, The transmission is really pulling some juice from the battery for some reason.

I'm not at all familiar with automatic gearboxes, so maybe this is normal. What are your experiences on this topic for your 3rd gen Pilots?
 

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It does seem like the readings are about 1V low. Try another OBD2 reader or measure the voltage at the battery with a voltmeter to compare. I doubt the voltage is really that low else you would be seeing other problems.
 

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Discussion Starter · #3 ·
I don't have another ODB reader, but I can check with a Voltage meter over the battery poles.
I agree that constantly running at just above 11V would probably cause some problems.
 

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I usually don't have volts selected, but here's 3 instances I did and motor is off. Motor running, volts seem to range/float high 12s to 14.1, iirc.
 

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Discussion Starter · #5 ·
I usually don't have volts selected, but here's 3 instances I did and motor is off. Motor running, volts seem to range/float high 12s to 14.1, iirc.
Do you mind checking what happens when you put the transmission into Drive and start driving?
 

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2016 CRV Touring AWD, 2005 Pilot RIP.
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Voltage is only part of the story. That said, its no longer unusual to see voltage at 12.5 when the car is running. That happens whenever the car has basically recharged the battery enough for it to wean itself off being fed by the alternator.
The 14v reading is likely right after starting.
 

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Do you mind checking what happens when you put the transmission into Drive and start driving?
Just a bit ago while driving, I observed a low of 12.6 volts to a high of 14.1 volts. Volts change rapidly up/down. The 12.6 volts displayed for a split second while idling and 14.1 volts displayed for a split second at 35-40 mph. Lots of readings up/down in the 13 volt range. Hope this helps......not a fan of snapping pics while driving.
 

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It's been my experience that voltage will fluctuate slightly depending on RPM's and load on the engine. I don't see any cause for concern unless, at any point, it's sustained voltage under 12 or over 14.
 
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