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Honda Pilot Batt light won't reset.


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whisperer
User

Dec 20, 2015, 11:31 PM

Post #1 of 16 (2305 views)
Honda Pilot Batt light won't reset. Sign In

Hi, first post, just found you guys…. :)

I have a customers car, a 2007 Honda Pilot, that smoked the original alternator and left her on the side of the road. I picked up the car and diagnosed it. Yes, no charging and it just looked nasty too. OK, easy stuff. Replaced the alternator with a store-brand rebuilt and it is charging 14.6 Volts and the batt is running at 12.2 Volts when the engine is off. Perfect……….. Not.

I test drove it and the batt light was off. Gave it back to the customer and she called me within the hour. The Batt light had flashed a few times, went on and off for a few miles and is now on solid. I did a house call and the voltage still checks perfect. I checked for codes and there is none to reset. Tried the dash reset (Odo) and could not get it to change. Cables and outboard stuff looks fine.

What's up with this? Is there a secret Honda voodoo that I'm not aware of?


Tom Greenleaf
Ultimate Carjunky / Moderator
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Dec 21, 2015, 3:09 AM

Post #2 of 16 (2296 views)
Re: Honda Pilot Batt light won't reset. Sign In

If alternator "smoked" that bad instead of just not charging you should be looking for heat damage to wiring and probably blame the battery tested separately from the car. New but more common if older they short inside especially when an alternator is asked to charge up a bad one.


12.2V with nothing on or draining like after 10 minutes point right to a bad battery or never did get fully charged up,


T



Discretesignals
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Dec 21, 2015, 5:43 AM

Post #3 of 16 (2289 views)
Re: Honda Pilot Batt light won't reset. Sign In

What is the PCM's system voltage on your scan tool. Have you done a full system scan to see is there are any DTCs stored in any of the modules?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


whisperer
User

Dec 21, 2015, 7:11 AM

Post #4 of 16 (2280 views)
Re: Honda Pilot Batt light won't reset. Sign In

"smoked" meaning slang term, not charging, not burned up. Wiring seems fine. Battery tests fine. 12.2V in car with no load. There is no significant draw on the system. No perceptive change with batt voltage after sitting for 12 hours so battery is not suspected to be bad. Customer still has car and it is starting and charging correctly for days now.


Tom Greenleaf
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Dec 21, 2015, 7:23 AM

Post #5 of 16 (2277 views)
Re: Honda Pilot Batt light won't reset. Sign In

If the 12.2V reading is correct on your meter that's not a good battery! How old is it? Just in normal use they flake of dandruff to bottom inside and over time which lowers it's power (AMPS) and if the pile of junk touches bottom of plates for any reason usually a bump or handling it they can totally short out inside. Low volts with some age is a clue. Normal is exactly 12.6V as each cell contributes 2.1V to the show.


12.2 shouldn't cause a warning but IDK if that is a reset or when cranking falls below any norms and remember it? If it falls below ~9V when cranking it should set off a warning on most but go right out when running so perhaps this set up doesn't.


Watch for voltage drop while cranking is a good indicator as that's the most load a battery should sustain acting just like you are doing a load test on the thing,


T



whisperer
User

Dec 21, 2015, 7:24 AM

Post #6 of 16 (2275 views)
Re: Honda Pilot Batt light won't reset. Sign In


In Reply To
What is the PCM's system voltage on your scan tool. Have you done a full system scan to see is there are any DTCs stored in any of the modules?


PCM system voltage is 12.2V. No DTC's stored as indicated from my OBD2 handheld scanner.

The charging system is functioning correctly as far as testing voltages show and the car has been driven for days with no loss of charge or apparent problems. It seems this is a problem with the BATT light sensing circuit, not the charging system or battery.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Dec 21, 2015, 8:33 AM

Post #7 of 16 (2269 views)
Re: Honda Pilot Batt light won't reset. Sign In

You didn't answer questions so what's the point?


T



whisperer
User

Dec 21, 2015, 8:51 AM

Post #8 of 16 (2266 views)
Re: Honda Pilot Batt light won't reset. Sign In


In Reply To
You didn't answer questions so what's the point?


T

AFAIK the only question you asked was "How old is the battery"?. It is a 2 year old Interstate that load tests good.

I do appreciate the help here but I am a 40 year master tech. I have already done all this "check the obvious" stuff. The battery is good, the alternator is charging well, the light is still on. That was the original post. Does anyone have experience with Honda BATT lights staying on after the alternator has been changed?


Tom Greenleaf
Ultimate Carjunky / Moderator
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Dec 21, 2015, 9:01 AM

Post #9 of 16 (2262 views)
Re: Honda Pilot Batt light won't reset. Sign In

40 years at it an still don't know about batteries!
I'm out. You seem to know everything so wonder why you are even asking,


T



whisperer
User

Dec 21, 2015, 9:13 AM

Post #10 of 16 (2259 views)
Re: Honda Pilot Batt light won't reset. Sign In


In Reply To
40 years at it an still don't know about batteries!
I'm out. You seem to know everything so wonder why you are even asking,


T


So, that's how it is huh? Do you always go to this nasty place when someone asks a question that you don't know the answer to? It does seem that you are the person that thinks they know everything, and if you don't, you get abusive. I am not going to worship you because you can type (poorly) on a computer. I am just a guy that came here ASKING a question because I KNOW I don't know everything.


Hammer Time
Ultimate Carjunky / Moderator
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Dec 21, 2015, 9:47 AM

Post #11 of 16 (2257 views)
Re: Honda Pilot Batt light won't reset. Sign In

Hey Whisperer, this uses a gauge control module that controls the light. Have you looked into that.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



whisperer
User

Dec 21, 2015, 11:08 AM

Post #12 of 16 (2248 views)
Re: Honda Pilot Batt light won't reset. Sign In


In Reply To
Hey Whisperer, this uses a gauge control module that controls the light. Have you looked into that.


Thanks for the reply HT. I have basically seen that there is one, but have not been able to get more info on it. It is supposed to be able to be reset like all later Nissans and some other Hondas by holding in the Odo reset button and turning on the Ign to the run position. I have tried that in all menus (Odo, trip and oil) and have had no luck, meaning it does not give me dashes that disappear that I am used to. Do you have more info on a reset procedure for this?


Hammer Time
Ultimate Carjunky / Moderator
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Dec 21, 2015, 1:59 PM

Post #13 of 16 (2242 views)
Re: Honda Pilot Batt light won't reset. Sign In

Here's what I can find in Alldata

Nothing about resetting

I did see a TSB about a battery reset if you have no communication with the module.










~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Dec 21, 2015, 2:01 PM)


Discretesignals
Ultimate Carjunky / Moderator
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Dec 21, 2015, 7:23 PM

Post #14 of 16 (2228 views)
Re: Honda Pilot Batt light won't reset. Sign In

With the key on and engine off, if you unplug the alternator 4 pin connector, does the battery light go out?


It is a fairly simple circuit. The L (white/blue) terminal is grounded by the voltage regulator to tell the PCM to turn the lamp on. The PCM then sends data to the cluster module, so it can illuminate the lamp. It may be charging, but either the alternator itself has some issue with the lamp circuit, or the circuit is shorted to ground all the time. Wouldn't be surprised if you got a bum alternator.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Dec 21, 2015, 7:30 PM)


whisperer
User

Dec 22, 2015, 8:46 PM

Post #15 of 16 (2201 views)
Re: Honda Pilot Batt light won't reset. Sign In

HT, THANKS! With this info I should be able to get to the bottom of this problem. Thanks for taking the time to post the diagrams so I can work through this. :)


whisperer
User

Dec 22, 2015, 9:02 PM

Post #16 of 16 (2200 views)
Re: Honda Pilot Batt light won't reset. Sign In


In Reply To
With the key on and engine off, if you unplug the alternator 4 pin connector, does the battery light go out?


It is a fairly simple circuit. The L (white/blue) terminal is grounded by the voltage regulator to tell the PCM to turn the lamp on. The PCM then sends data to the cluster module, so it can illuminate the lamp. It may be charging, but either the alternator itself has some issue with the lamp circuit, or the circuit is shorted to ground all the time. Wouldn't be surprised if you got a bum alternator.


Discretesignals - Thank you for this info. I will schedule the car back in and do what you suggest. Makes total sense. I did some other work on this car about a month before the alternator died and there were no lights at that time so it was not a ongoing issue before that time. The wiring looked OK at first inspection. I'm thinking that maybe the regulator is wrong/bad internally on the L circuit but the field driver circuit is OK? (Hoping anyway). You might be right, a bum rebuilt alternator.

The customer is on vacation for a few weeks but when they return I will get the car in and report back what solved the problem. Thanks everybody for your help on this.






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