[riverman]

second the battery... put a booster pack or charger on it and see if it fires up.

The battery already reads 12.4V the next morning. Chances are this is not a battery issue. This looks like an immobilizer issue to me. It is possible that there is an open wire or wiring connector somewhere, so playing with all connectors that you can reach could solve the problem, but that's a long shot. I had this issue with a new 1988 Mazda and the dealer couldn't find the issue, because it was intermittent. In this case, the car would die irregularly, then restart after it sat a while.

The brightness of an interior light is a kind of voltmeter, depending on its brightness. It can indicate the battery voltage while cranking. An interior light will dim somewhat during engine start, but will stay on even brighter after the engine starts and the alternator kicks in. I do not know if pushing the starter button turns off your interior lights like it does with other electrical systems, in which case this wouldn't work.

If an interior light is off after an attempted start, it is probably a dirty battery terminal causing the issue. If you turn the ignition on without starting the vehicle, with the A/C on, this could draw 25 amps or so. The radio draws about 5 amps. If the interior lights are pretty bright with the ignition, radio, and A/C on, and the engine is off, chances are it is not a battery or a dirty battery terminal that is causing your issue.

I like the idea of disconnecting the battery to reset the car's computers. This could take many hours, so short the disconnected terminal with the other terminal to help the car's computers fully discharge the capacitors contained within. THAT may take 30 minutes or more under some circumstances to fully and completely reset the vehicle computers. Otherwise, such a reset could take a day or more.

 

[riverman]

When the Green Key is blinking on your dashboard, the Immobilizer Module is failing to recognize you transponder chip within you key. You would need to reprogram your keys to the Immobilizer Module…

I think this is likely an immobilizer issue, that may not necessarily require an expensive dealer visit. Read the previous post I have on this issue, which discusses a reset for the car's various computers, that would include the immobilizer module(s). I believe the immobilizer module is linked to another module in the instrument panel or elsewhere.

I had this issue and this worked. It took me a week or so to figure this out and try it, and it worked for me. I haven't seen this solution elsewhere.

 

[riverman]

Not an electrical engineer, eh? If you are concerned that there are capacitors that will stay charged for more than a few seconds, a quick press of the brake pedal will discharge any residual power in the car/van electrical system.

Anything else that remains in 'memory' after that is due to some sort of non-volatile storage (flash, eeprom, etc.)

-Charlie
[/QUOTE]

In general, you would be correct. Capacitors usually discharge in seconds.

Well, I had an experience after playing around with my 2016's electrical system. Afterwards, the immobilizer prevented the vehicle from starting. It would start, run a second or two, then die. I suspect that I had disconnected and reconnected some connectors under the dash with the ignition on, thereby causing the problem, due to my carelessness.

I messed with a Foxwell NT-650 for more than a week, getting several proprietary bus error codes. I studied the service manual. I tried everything I could think of to get the vehicle started. Nothing worked. Then, I remembered something going back quite a few years. So I grounded the electrical system for an hour or so, and then I was able to start my Odyssey.

This is what I had remembered. A specialized capacitor can be used as small battery if the current draw is very small. Today they might be called super capacitors. They have a very slow self-discharge rate, unlike the caps we are familiar with.

My old VHS video player kept some things (I forget what) in memory for almost an hour after the power was removed, and eventually it wouldn't retain that memory. When I contacted Panasonic, a tech rep told me a capacitor was used as a battery, and that this cap had failed. He told me which part to replace (something that probably wouldn't happen today). This fixed this issue. I didn't really believe it would work until I tried it. The part was a small, cylindrical, proprietary capacitor. It cost a bit more than your average cap, too.

There isn't any other explanation I can think of as to why my car would start normally after grounding the battery terminals. This had worked. And it was free and easy. None of us would really know what is actually inside these Odyssey modules, right? I surely don't.

 

[riverman]

For a while, several years ago, I had a problem with the immobilizer on my '99 Odyssey. I got deep into debugging it, and eventually it fixed itself. Probably some posts on that over on the gen2 forum. Some things from that which may be relevant here (not confirmed true on these cars, though):

- the immobilizer system is only used at start. Once the immo check passes and the ECU allows the car to start (in that car, it would allow cranking, but block fuel injectors, ignition, and maybe the fuel pump as well, from memory), it will run until turned off; immo failure will not kill a running engine = would be a big safety issue.

- (if you expect an immo issue, I would get exact confirmation of exactly what that green light should be doing on a working car) On my '99 when the key went to ON, the green light would come on for two seconds while the ECU/immo system did their check for the RFID chip in the key. After that (before and after starting), if the immo check passed, the green light would go out. If the check failed, the green light would flash forever. While driving around, it would remain off. After driving, after removing the key, the green light would flash about 5 times and then go out - as a signal that the immo is re-initialized to prevent starting next time.

- (based on other stuff in this thread, I am suspecting a voltage problem) Good general tip above on noticing light intensity as a voltage indicator, without needing a voltmeter. A related tip for testing general no-start conditions is to turn the headlights on and watch to see how much they dim while the engine cranks. BTW, a dip to 9 or 10 Volts during cranking may not be a problem, and some amount of dimming should be expected. On a couple of my older German cars, at least, they have a feature where the headlights are automatically switched off while cranking the engine, just so all the juice goes to the starter. My old Porsche, since it thinks it's a lightweight race car; and my old air cooled VW Vanagon because it needed all the help it could get.

Good writeup. Information is as useful as it is specific. I would suspect you had a similar issue as mine, and having the vehicle just sit for a week or so solved the problem. Shorting the battery terminals on the vehicle side does the same thing, but much faster.

A 9 (or maybe 10 volt) cranking drop is normal. The minimum is around 8.5 volts or so when all is well. Much lower than this, the battery is discharged or dying, or a terminal somewhere has excessive resistance, and will feel hot after an attempted start.

After cranking, if the engine doesn't start, the voltage should return to pretty close to the 12 volt reading observed before attempting a start. If the engine starts, the system voltage should be in the vicinity of 13.5 or a little higher volts (On Odysseys - this can differ a bit for other models and brands) while charging or (just maybe) 14 volts at the battery. The charging voltage will go down slightly as the alternator re-charges the batttery from sitting and starting. I have a voltmeter permanently installed so I can read these numbers.

 

[riverman]

Did the dealer replace this

I had a similar issue on my 2016 Odyssey. To answer your question - no, I never took my vehicle to a dealer. My ego will not allow me to do that. I would fall on my sword first.

I'm not sure what your issue is, or if you have a starting problem. This thread has some good information. If you had disconnected and reconnected certain wiring terminals with the battery connected, perhaps including the PCM connectors, this could have caused your issue. Maybe a lightning strike nearby or a static discharge caused the problem. When I had a similar issue (self-induced) the immobilizer would flash about six times and the engine would start for a second or so, then die. If this is your symptom, you may possibly solve your issue as I solved mine.

Somewhere else here, a power reset involved five seconds of shorted battery terminals. I'm not sure a five second interval would do the job completely. Very tiny component and current values could take more than a few seconds to completely discharge everything. Some capacitors can keep circuitry activated for many hours. If you tried a five second reset, and that didn't work, it doesn't cost anything to do this for an hour.

Maybe you would let us know if shorting the battery terminals works for you.

 

[riverman]

Battery is fine. Brought to Advanced auto for a load test. Hold charge fine. Now I am lost

I had a failing battery. I needed a jump start to get the vehicle running. I drove 15 minutes to an Advance Auto Parts store, and they checked the battery as good. I t held enough charge for AA to tell me the battery was good.

I disagreed, and waited around for about 45 minutes and then, the car wouldn't start. After that, the battery check failed, and Advance Auto Parts replaced the battery under warranty.