2000 Honda Odyssey Van -

This may be a rather lengthy post but I wanted to be complete and see if anyone has had this problem or could steer me in the right direction:

Problem: The Battery, Brake and all Door Lights all flicker intermittently. When this occurs, the alternator stops putting out voltage and the system voltage drops to battery voltage (12 volts).

What I have done: I have replaced the following components: Battery, Alternator (rebuild from parts house, not OEM), Electrical Load Detector (ELD), Powertrain Control Module (used PCM flashed at dealership), Ignition Switch. After replacing each component, the problem persists without any change in the flashing lights.

I have subscribed to ALLDATA to find wiring diagrams and checked all grounds in the engine compartment and under the dash.

I have monitored voltage readings at the alternator output, the 4 wire input plug and the cigarette lighter with the following observations:
The alternator output goes to12 Volts at times. When this occurs the lights may flash but not always.
The lights never flash when the alternator is putting out voltage.
The BLK/YEL wire on the alternator input plug seems to fluctuate up and down a lot.
I have seen the cigarette lighter and BLK/YEL wire go to 12 volts when the alternator shows 14+ volts.
I have seen the rebuilt alternator output fluctuate between 14 and as high as 18 volts at times but is mostly steady at 14.8 volts.

The Van has 360K miles on it and a couple of years ago had the heads reworked. Runs great.....except for this issue. Only let me down once when it died due to the alternator not charging during this problem. This has been going on now for close to a year. The car does not owe me another trip to work but I hate to giver her up for this issue. Kind of like ditching an old friend at this point.

Any HELP would be GREATLY appreciated!

Thanks - Piv

The alternator is most likely the issue here. Parts house chinese rebuilts are notoriously bad. I've experienced it myself. You want to make sure you stick with Denso remans only. Did it do this before changing this alternator?

 

Yes - it did do this before changing the alternator. I was thinking about changing the alternator again and going to a Denso. Just seemed somewhat unlikely that two alternators would have the same issue.

 

I agree. It sounds like it's not the alternator then. Are you able to duplicate it when you want to work on it? A scan tool that could see what the ELD is seeing, and what the alternator output command is when this happens, would be helpful here, too.

Can you be more specific about your observations of the BLK/YEL wire to the alternator? When you say fluctuates a lot, just what exactly does that mean? Just 12-14 volts or are you seeing lower than that?

 

The main wire that runs from the alternator connects to a black plastic relay box on the passengers strut tower. A second wire connects from that box to the battery. Theoretically, if the wire from the alternator were loose at the black plastic relay box, it would probably act as you describe.

 

Verify engine grounds are clean and in place. Corrosion at either end will act like this. May be s good time to revisit many of the grounding spots. Focus on the high current ones first (fans, blower, ac clutch, etc...).

Alternator likely ok but if it’s poorly mounted or a missing ground it will not have that ground reference needed to operate correctly.


Sent from my iPhone using Tapatalk

 

Also, the ELD unit shares a ground with several other components just in front of the cruise control box at the passenger's inner fender. Try taking that ground junction apart, cleaning it, and putting it all back together. It's just a bolt with a number of ring connectors on it. By chance does your window washer pump work when the alternator ISN'T charging? It shares the ground point.

 

Also, check fuse 41 in that black plastic relay box to see if it is loose or corroded. It serves as the connection between the alternator and the battery.

 

Instead of taking them apart and cleaning them, hoping to fix it, you should be able to do voltage drop tests across them and see if they're OK. Just make sure the circuit is loaded and current is flowing.

 

Wow - really appreciate the inputs here. To answer some of the questions.
I can not duplicate the problem....and I think I have tried everything. It happens very randomly but is happening with more frequency as time goes on. Most often it occurs a few times when driving to work- 35 mile drive. Very seldom happens when stopped.
I have a scan tool but no codes are showing. This is a pretty good reader but I'm not really sure how to see the alternator output command in real time. I'll investigate this.
The BLK/YEL wire that goes to the fuse box fluctuates sometimes by going from 0 to 14 volts. The meter starts to bounce all over the scale. This is especially true when the dash lights are flashing.
I will recheck the grounds on the ELD and try the washer when it acts up. I never would have thought of that one for sure. . Voltage drop test also sounds like a good way to go. Don't believe I have every tried that technique.
The alternator ground may be a strong possibility. I do have broken bolt on the mount. The alternator seemed secure enough and the bolt may be a real issue to get out but I should have dealt with it when I noticed it anyway. I'm headed out to try to take care of that right now.
I'll also take a look at that black plastic relay box and the connection going from the alternator to the battery.
Thank you all VERY much. Y'all are great!

 

R&R'd the alternator to verify the mounting bolts are nice and tight. But no ground wire on any of the mounting bolts so I am assuming the alternator does not have an external ground wire.

Also unbolted the ELD ground point, cleaned with wire wheel on Dremel and it's also nice and tight.

Went for a test ride with same problem.

 

There is no ground wire at the alternator. It's grounded to the block directly. You need to make sure the block grounds are clean and tight.

 

i am wondering if the battery might be cooked, if you replaced the alt because it wasnt charging then the battery could also be cooked from that issue, when i had dash lights problem i had changed the alt battery and eld in the same shot, problem solved

 

How old is the battery??

 

Thanks - I did replace the battery but the problem remained.

Lately I have done some research on the voltage drop test. Can't believe I've never tried that before. With the van running, the voltage drop test was good from the alternator to both ground (alt case to neg battery = .1 volt) and power (alt output to pos battery = .7 volt). Since I have suspected the BLK/YEL wire, I did a voltage drop test from the alternator 4 pin connector to the BLK/YEL wire at the Ignition Switch and it is also good, even when the dash lights are flashing and the alternator output has dropped to 12 volts it remains unchanged at .2 volts

Sounds extreme but I am contemplating cutting the BLK/YEL wire and temporarily running alternate switched power though a 15A fuse to the BLK/YEL wire input to the alternator - just to see if that corrects it. At least I can confirm if that wire is the culprit or eliminate it.

Not exactly sure what the other wires do and if they are input or output. I believe the have to do with controlling the alternator's output at low or high mode and activating the charging system dash light.

 

Here is a pretty good desc of ELD, if that helps

Honda-ELD

 

Piv,
I also have a 2000 Odyssey with what sounds like the same exact symptoms.

I replaced the Alternator with a re manufactured Denso - did not solve the problem.

I took it to a mech. who ran scan and said possible known TSB about problems with ignition switch/wiring harness causing flashing dash lights. Replaced the wiring harness (ODY original) at great expense - did not solve the problem.

Will begin checking all grounds asap.

Searching for real answers like you - would be happy to hear if and how you solve this problem.
thanks, John

 

PIV, John4444,

I just replaced my alternator (Amazon - not a Denso) yesterday and I'm having the same issues (225k). I read a post (unable to send link) for Honda accord and it seems to be a common problem with the 3.5 VTEC engine.

I will let you know if I fix the problem.

 

Thanks for the ELD information. Even though I replaced the ELD and the PCM, I am wondering about it since my alternator output does vary a lot at times for no apparent reason. I think I'll take another look and see if I can monitor the voltages. My wiring diagram labels the two lines coming from the PCM to the alternator as "Alternator Signal Control (ALTC)" and "Alternator FR Signal (ALTF)". Not sure about the ALTF wire but evidently, these are two inputs that control the alternator output via the PCM.

I think I'll see if I can find a scan tool that can monitor this and also hook my multi-meter up to see if I can determine what they are doing when the lights start to flash and alternator output starts to vary.

 

Piv - Can you provide any more input on specifically what lites flicker? And also when.. at idle? driving? over bumps? on freeway? I kind of think it is a short, but the more info the better. Trying to be detective.

 

Piv - do you use Torque or Torque Pro app. During my alternator woes, I used the Torque Pro app with my cheap bluetooth ELM OBD2 reader and was able to monitor key attributes such as rpm, voltage, etc and then was able to log these and download into a csv file and import into excel. Over several rides/days I could see the voltage drop occasionally and determined it had to be the alternator, even though I put a new (off brand) alternator in a few months earlier. A new rebuilt Denso resolved that issue.

 

Torque or Torque Pro won't be able to see the ELD data. You need an enhanced data scan tool for that.

Foxwell NT510 or NT520 is a good option on a budget.

 

A lot of weird electrical problems can pop up due to a bad alternator. If your current alternator is showing voltage swing of 12 - 18, that is a bad alternator. I would change that first or rebuild your old denso. I rebuilt mine a couple of years back and its been performing great since. https://www.odyclub.com/forums/24-1999-2004-odyssey/261601-compressor-pulley-has-side-side-play.html

 

My negative return cable from the battery to the trans is brittle and needs replacing. I will be changing it hopefully Thursday or Friday when the rain stops. I have also replaced the positive terminal post and morning drive to work - no flickering of the lights. Will keep you posted. View attachment 142943

 

The dash lights that are flashing are the Door Lights (all of them), the Brake Light and the Battery Light. I think they all share a BLK/YEL wire, It happens totally at random. Definitely not associated with bumps or any electrical components being turned on/off or application of the brakes or turning, etc. The windshield washer does work when the problem shows itself (previous question). The only constant seems to be that the lights/alternator output problem won't happen when at idle. When it happens at speed and you stop the van, it may stay on for a brief moment but not long enough to get under the dash or hood to troubleshoot.

Today I was monitoring the Alternator Control Signal (ALTC), WHT/GRN wire on the alternator plug. When the alternator drops off and the lights are flashing, this voltage goes from the normal 2.3 volts to zero. Not sure if this could be a cause or simply the effect of the alternator output going to 12 volts.

I just might change the alternator again. I'd be glad to pay the dealer cost for an alternator if it would fix the problem. Just having a hard time convincing myself that two alternators could have the exact same issue. I may have to dig deep and just do it to know for sure.

What I'd really like to be able to do is confirm the inputs at the four pin connector are all good but since they are only giving faulty readings when the problem happens, I am having trouble telling if one of the four pin connector wires is the cause of the issue or they are giving bad readings because of the alternator output.

I'll also be looking for a Faxwell Scanner.

BIG THANKS for everyone's help cause I'm stuck - BIG TIME - on this one.
Piv

 

Today I was monitoring the Alternator Control Signal (ALTC), WHT/GRN wire on the alternator plug. When the alternator drops off and the lights are flashing, this voltage goes from the normal 2.3 volts to zero. Not sure if this could be a cause or simply the effect of the alternator output going to 12 volts.

According to the service manual, the ALTC wire should be outputting approximately 8V when the engine is fully warmed up and running. I've attached a pic of the page from the manual.

 

Your comment about the 2.3 volts on the alternator control output circuit is interesting. I'm guessing that the 2.3 volts you're seeing is an average voltage and that the PCM is sending a pulse width modulated signal to the internal regulator in the alternator. So, what's really happening is a 12 volt square wave with a certain on and off time. You would need a scope or a fast graphing meter to see what's actually happening there. Your DVOM is too slow to see the actual activity on that line.

You said you replaced the ELD, but did you check the power, ground, to the ELD, and the signal coming out of the ELD? It should have a 12 volt input, a ground, and then an output to the PCM. You need to make sure the power, ground, and output from the ELD are all good. The output will change based on the amount of current flowing through the ELD to the rest of the car (basically the demand on the alternator.) That ELD signal is sent to the PCM and the PCM outputs a square wave to the alternator to vary the output of the alternator. It sounds like that control output to the alternator is telling the alternator to stop putting anything out.

I would be suspect of the 12 volt ignition feed to the ELD, also. That is also the 12 volt feed to the alternator's white/blue wire (L circuit) and black/yellow wire (IG circuit.) If that feed is going to 0V then the ELD would lose power and the ELD would stop sending a signal to the PCM which might explain the white/green wire going from the average 2.3 volts to 0 volts. That power feed goes through the ignition switch and (either the #6 or #4 fuse in the driver's underdash fuse box, depending on what wiring diagram you look at) and may be losing power. It may be as simple as a bad fuse or ignition switch.