Our local dealer asked us to do this idle stop software update recall (I suppose it is TSB (A23-008)) for our 2020 Odyssey when we called in for an oil change in November. It takes a day for them to do the software update.

After that, the idle stop never engages again. The dashboard shows "Auto Engine Idle Stop Unavailable" each time the vehicle comes to a fully stop. Our idle stop works properly before they did this software update. I brought back for them to check a week later. They tested for another whole day and said all the systems were normal and it could be conditions that does not meet the criteria to engage the idle stop.

It has been a month; the idle stop unavailable problem remains. Anyone has similar problem after idle stop software update? Dose TSB (A23-008) released by Honda apply to 2020 Odyssey? Any suggestions?

 

It could just be normal operation. The software update is designed to make the conditions stricter for idle stop to engage. So you could have a weak battery or something, especially if you still have the OEM battery.

 

We bought the brand-new Odyssey from the Honda dealer three years ago and never change the battery. The dealer did the multiple point inspection at the same appointment of the idle stop software update and said the battery is normal.

Before the update, when the engine restarts after idle stop, the headlights would flash a little bit. Is this an indication of weak battery? But, it had been doing that since the car was brand new, at which time the battery could not be weak.

I called Honda American, they asked me to bring to the dealer to check again. If they still don't figure out anything, that means I will lost the idle stop feature due to an software update.

 

So you lost the idle stop feature....
Just think of the money you will have saved in the long run with less wear on your starter, battery and not having to buy the IdleStopper.

 

I have the same exact problem.

 

Just got this idle stop update done yesterday. Shit will literally not work unless ac is at lowest fan speed and not on high or low temp. Also gave me some other message saying it cant engage because battery is charging. This update sucks!

 

Sounds perfect tbh

 

Related or maybe not, we too have a 2020 Odyssey, had several updates and one being the idle start/stop issue. For that, we would have problems when we would stop and the car would turn off the motor, it would not restart the car and we had to put the car in park, restart the car and usually worked. We dropped the van off or a while during holiday breaks and after the update over Christmas, the car will completely shut off with ZERO power, we couldnt do anything to get the power to come back on and literally nothing would fix it until I go so pissed and slammed the door or hood and lights came back on. This happened several times over the weekend until we could get into their service dept (South Pointe Honda, Tulsa OK) on Monday. Van was looked at and they said it was a loose connection at the battery, said to tighten the battery connection. I was already irritated and then their response was BS because I first tried to jump the car when it happened after the recent service, thinking it was a dead battery and sure enough it was still not get power to anything, even with the jumper cable attached. So we decided there was something they were hiding or not even checking/servicing the car, but it worked when we get it back the at the end of the day(1/6). Then the %^&* hit the fan with the last incident was when my wife and daughter were driving in the van and this "no power" happened again the very next day (1/7/25). She had no brakes, no steering and the steering wheel locked, then having to coast until she came to a stop, luckily it was at a intersection and only coasted half way into the road. What would have happened if she was on her weekly trip from Tulsa/OKC going 80mph, I was justifiably furious because we just had the van in their service for the updates just a week ago and my family is now at risk. This isnt a issue of the van being dead when stopped or at home, this is now a danger to drive as it could happen at any moment when driving. I demanded they bring a tow truck and get the van. Fast forward to their reply why this is happening. South Pointe Honda said it was the connection at the battery (negative terminal). I know this is NOT the root cause. I am not a ASE certified tech, but I know enough to know, this is BS. I am thinking the during the several updates, routine maintenance and recalls, something related to a grounding or software FUBAR is wrong. We had the following issues looked at: bluetooth issue, the idle start/stop, had transmission serviced for it's 60k mile routine and brakes resurfaced due to shuttering during hard braking. Has anyone heard of this before? I have tried to find info online and this forum topic was the closest I could find that was applicable and looking for help. Thanks in advance 2020 Honda Odyssey, V6 - 58k miles

 

@trbright
Welcome to the ODY Forum!
Battery problems have caused a lot of different problems in the GEN5 ODYS.

Have you ever replaced your battery since buying it new? 4 years of battery age in these ODYS can lead to a lot of problems. Most people are replacing then between 2-3 years of age due to the electronics on all the different modules in the ODY require a higher voltage to operate correctly. A few people have replaced their batteries in a 1-1/2 years. I replaced mine in 2-1/2 years due to slow operating sliding doors. That fixed that problem with no doubts. Having the Honda Dealer check your battery for charge level does not work well either. They have reported battery's' being good, and owners replaced the battery with a new one and lo and behold their problems was resolved. I am not going to say it fixes everything... but at the cost and having it not start or reporting faulty problems that do not really exist, it is a cheap repair.

Your battery negative cable to the chassis ground could also be corroded and making intermittent connection. The problems you and the wife is having sounds like the battery or a grounding problem. IF this is the problem remove the bolt and washer and clean off the corrosion, wire brush the chassis and reinstall the cable.

 

thanks for the quick reply and yes, newish less than 2yrs old battery, even had it trickle charged after the first incident. I am too thinking there is a systems ground, and once I can go get it, I plan to chase it down. they still have the van and will check for new ground cable or connection, etc to see if i can quickly see a new component on the root cause to have more validation in my frustration, their "fixes" dont make sense from what I already checked or tested. Now they want to charge me for a new battery installed (didnt get preauthorization) and said they may put the rental on my bill for the days they have had it.

 

From what I know and found online so far. Here's a breakdown of why their explanation doesn't add up:

Why "Loose Battery Terminal" is Unlikely:

• Complete Power Loss: A loose battery terminal usually results in flickering lights, dimming accessories, or difficulty starting. A complete loss of power, especially while driving, points to a more serious problem within the electrical system.
• Steering Wheel Lock: This is a major safety concern and is unlikely to be caused by a loose battery terminal. It suggests a disruption in the power steering system or the electronic steering lock mechanism.
• Recurrence After "Fix": The fact that the problem happened again immediately after they "fixed" the battery connection strongly indicates they misdiagnosed the issue.

Possible Technical Explanations:

• Grounding Issue: As you mentioned earlier, a faulty ground connection could be the culprit.
• Faulty Ignition Switch: A malfunctioning ignition switch can interrupt power to the entire vehicle. I am really thinking it has something to do with the Idle start/stop*
• Main Relay or Fuse Box Issue: A problem with the main relay or a critical fuse in the fuse box could cause a complete power loss.
• Wiring Harness Problem: A loose or damaged wire in the main wiring harness could be intermittently cutting off power.
• Body Control Module (BCM) Malfunction: The BCM controls many electrical functions in the vehicle. A faulty BCM could be causing the power loss and other issues.

 

Have you found what could be causing the issue?