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2002 Honda Odyssey - Battery, brake and all door lights intermitantly go on briefly and off

Currently the charging system indicator, brake and all door lights come on occasionally but only stay on for a 1-2 seconds and then go off. Since both the battery and alternator have very recently been replaced, I’m wondering if the problem is something like a loose wire, and if so, how to find it? I took it to my local independent mechanic today and the battery and alternator tested OK and the main electrical wires are also OK. When he started the van and wiggled the ignition key, various instrument lights would go on and off. He suspects that the connectors of the ignition switch wiring harness don’t have a solid connection (corrosion?) and that replacing the wiring harness may solve the problem.

Does this make sense or there other possible causes of the problem that I should investigate?

I have become concerned about traveling any more than a few minutes from home, since if the charging system indicator stays on permanently, I cannot drive for long before the battery would die.


Replacing the ignition switch and wiring may solve the problem.You can try a spare key in case the one you are using is worned and doesn’t make good contact. A heavy key chain can damage the ignition switch after 16 years.

get the ignition switch replaced. My opinion, more likely than wires. If it is the connectors to the switch, they perhaps can be cleaned up or tightened.

Or the wires cut off and new connectors spliced in, much cheaper than replacing the entire harness, unless this is a small short harness…

Thank-you for your suggestions. I will try using a spare key with nothing else attached to the key chain. I’ll also mention the ignition switch to my mechanic.

Thanks again.

Unless the vehicle has been in a flood, there should be no reason the entire wiring harness needs replacement. There may be one connector that does however. I’d guess it would be considerably less expensive to pay to figure out which it is than replacing the entire harness. If the lights are flashing on and off on a one or two second interval, the flashing goes on for quite some time, that’s more likely a circuit breaker has detected a short circuit in the wiring somewhere.

If the trouble occurs while tapping the ignition switch it would be a good sign that the trouble is there. Rather than suspecting the wire harness I would really look at the ignition switch itself or the connection to it. If the connector is loose then just crimping the connections a little should solve the issue. Cheap fix if that is the cause.

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Thanks for all the help. I am having the ignition switch replaced later this week. The ignition switch/wiring (Honda part number 35130-S0X-A02) seems not to include any keys, so it does not include the full switch that includes the lock tumblers. There is also a question about an immobilizer unit, but I don’t think my Odyssey has one.

One thing I have noticed is that when the (battery, brake and all door) lights come on for a few seconds, I can get them to go off immediately by turning on the headlights. Is this information of use in helping to pinpoint the cause of the problem?

I also have the DRL (Daylight Running Lights) dashboard light on most of the time. It goes off intermittently, but will also go off when I turn on the headlights. Is this related in any way to the above issue?

Thanks again for your help.

The ignition switch is a separate piece that is operated through the key lock tumbler. From what you stated earlier it seems that replacing the ignition switch should fix the issue since wiggling the key seemed to aggravate the issue. I would tap on the switch itself to verify that before replacing it.

I had the the ignition switch replaced a week ago. Worked OK the next day, but the day after the lights came back on/off again!

The battery (new Interstate) was replaced on June 6 and the alternator (rebuilt) on July 20, so they seem unlikely to be the problem. I plan to go back and have him recheck the alternator again.

What is interesting is that they seem to come on/off only at low RPM, like when coming to a stop or stopped. Also, they will go off immediately when I turn on the headlights or even the turn signals. One thought would be to always have the headlights on when I’m driving?

Turning on the headlights prevents the other lights from intermittently blinking, and everything works correctly then? hmmmm … that could possibly be a problem with the alternator. It could be the alternator is producing voltage spikes or isn’t properly regulating the output voltage under low electrical load conditions. Your idea to just drive with the headlights on low beam until the issue is resolved makes good sense.

There is a service bulletin to address this problem.

“Electrical noise coming from the cooling fan circuit can cause the warning light to flicker momentarily.”

The repair involves replacing the alternator with a revised part number. The bulletin does not explain what was changed or added to the replacement alternator to solve the problem.

I’m a little confused. Is the cooling fan circuit part of the alternator?

Also, I have had the alternator replaced twice (once on June 15, 2017 and once on July 20, 2018). Both times the alternator was a rebuilt unit. The replacement P/N (31100-PGK-A03RM) in the SB is different than the P/N (P/N 31100-PGK-A02) it is to replace. Maybe the rebuilt replacement alternators are not the correct units and maybe they do not solve the problem? How to proceed? I don’t want to pay for a third alternator, which would probably cost more than the previous replacements. Should I go to a Honda dealership to see if they can do a replacement without charging for it?

Electrical noise from the radiator fan motor might be causing a disturbance with the charging systems Electronic Load Detection system on some vehicles but that may not be the problem with your vehicle.

According to other Odyssey owners it is normal for the door ajar, brake and charging system lights to illuminate when the alternator is failing, the door ajar light confuses the problem making it seem that there is a weird electrical problem. There are several reports of failures/warning lights shortly after installing an aftermarket alternator, perhaps there is a quality problem or they just don’t work well with the ELD system.

The cooling fan circuit is not part of the charging circuit but like all the other electrical systems of the vehicle they are all connected to the main power system which is the battery and the alternator. Electrical noise can at times be generated by one of the components tied to the power and that noise can travel through the power leads and possibly effect other things tied to the power bus. Engineers will eliminate that kind of trouble by placing electrical filters in the electrical system if it is needed. It may be that a filter circuit was added to the replacement alternator after this issue was discovered with the cooling fan circuit.

The warning lights are usually tied into the field circuit of the alternator so they can be tested when turning the ignition ON before the engine is started. So if there is some sort of alternator trouble it can effect the other warning lights also besides just the battery warning light. If the problem is due to electrical noise a good electrical tech will know how to check for it and fix the problem. Finding that person can also be problem, but a place that specializes in electrical problems should have such a tech on hand. Going from your description of the trouble and noting the headlight comment my best guess is the issue is with the alternator, especially if this problem happened after the alternator was replaced. Even though the alternator checked okay intermittent problems like this can make things seem okay most of the time, until it acts up. If the cooling fan circuit is the real culprit here I would filter the line at the source of the problem.

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I had the DRL module replaced thinking that it may somehow be related. It fixed the DRL issue I had (the DRL instrument light was on most of the time), but the battery/brake/all door open instrument lights on/off issue is still there. Putting on the headlights seems to be a workaround solution. I’ve already spent to much and don’t want to spend more chasing an elusive electrical issue.

Thanks everyone for your help.

You’re welcome for the help. I suspect that turning on the headlights is causing the alternator to react to the higher current drain on the electrical system and that makes changes to the alternator field current at the same time. I am pretty certain the problem is with the alternator.

Yes there is no telling what it could be. You’d need lots of electrical equipment to pinpoint the disturbance in the connection. My Honda Accord lights comes on when I hit the brakes and goes away when I accelerate. Must be that the alternator is overcharging. You can buy battery to alternator plug ins to your lighter to watch how it fluctuates. I’m still waiting to get mine to test it out.