Power System Problem dash warning

[green1]

I’m a new owner, only a week in and I see this error on the dash after partially charging at a Tesla 7kW home wall charger: “Power System Problem, Power May Be Reduced”. I don’t know it has anything to do with the charger, it’s just a normal charger and the car charged fine. I have seen on this forum people receiving this error after using DC rapid chargers, with the additional error “Quick Plug-In Charging System Problem” which I am not receiving.

The error was initially quite intermittent, coming and going for a day or two (warning on dash when the car is put into ready mode or comes up later during driving). I then charged it fully at a 4.8 kW street charger and it’s still there.

Over the next day or two I notice that the error is increasingly present and especially comes back during the day when it’s hot and isn’t present or is barely present during night time driving when it’s cool, making me think this has something to do with temperature.

Plugging in my OBDLink reader, I initially read the following error code:

P0E12(08): Pending, Confirmed, test not completed during this operation cycle.

And after 2 days driving normally to see if the ECU is able to clear it on its own:

P0E12(08): Test failed (current drive cycle), Pending, Confirmed.

I’m in contact with my dealer as obviously this should not be occurring on a recent purchase (used 2020 reg, only about 3000 miles, ex demo Honda approved), I haven’t heard back from them yet.

I wanted to ask if anyone else has experienced this (I could not find this on the forum, or for everyone else it seemed to go away and was spurious and the OBD code was never read) or if anyone can make sense of the error from the info provided.

Searching the error code online says the error refers to “HV battery pack coolant heater A open circuit”, which I guess would mean the battery can’t be preheated properly if the temperature is colder? But then the error seems to go away when it’s colder, so a bit confusing.

Thank you!

[Deleted User 473]

It's not something I recall being reported here previously.

Don't forget that the battery takes a while to cool down or heat up, so the immediate ambient temperature is not always as relatable to the issue as you might think.

I wouldn't be surprised if that error code is slightly different for this car. It might be worth subscribing to the Honda technical resource to look up the code exactly. i think you can get one off 24hour access for 10 euros (I've never tried this).

Whatever it is, something is most likely broken. You can try the usual things, detach 12v battery , give it a full charge, check all of the fuses and go from there. Unlikely to be the cause but worth a punt.

[green1]

It's not something I recall being reported here previously.

Don't forget that the battery takes a while to cool down or heat up, so the immediate ambient temperature is not always as relatable to the issue as you might think.

I wouldn't be surprised if that error code is slightly different for this car. It might be worth subscribing to the Honda technical resource to look up the code exactly. i think you can get one off 24hour access for 10 euros (I've never tried this).

Whatever it is, something is most likely broken. You can try the usual things, detach 12v battery , give it a full charge, check all of the fuses and go from there. Unlikely to be the cause but worth a punt.

Thanks EEEE. I didn't know that website existed, it's https://www.techinfo.honda-eu.com/ for anyone reading in future, and it's 10 euros for 1 hour . I think I will try that, just so I know the dealer is actually resolving the problem.

Silly question, but why is it thought that checking fuses or detaching the 12V would have any impact on a problem that the dash says is affecting the HV system?

[green1]

I have signed up for an hour there to get the info on the error code. It is 'HV Battery Module Heater Control Circuit/Open', so definitely related to the system for heating the HV at low temperatures.

I'm not sure if I'm allowed to post the info/diagrams from there, but according to the website this particular fault can be caused by a series of potential causal factors, including coolant heater circuit failure, coolant pump circuit failure, coolant leak, coolant air inclusion. So yeah, doesn't look good and does need to be checked out ASAP.

So, in addition to the car being limited on range, it is now also a seasonally restricted car .

Oh well, fingers crossed they fix it properly.

[Deleted User 473]

I wouldn't post the pictures on here, as much as we would like to see them.

I suspect the battery heater is not contained within the battery pack, and instead a single heater controls the coolant used for interior and battery and a pump/valves divert as necessary.

Without a bit more detailed understanding, i'd say it would be hard to track down the cause in a reasonable time frame. I assume the coolant level under the bonnet is OK? No visible leaks? Its still worth doing the 12v reset if you haven't already (although maybe hold off on this if you are taking it to the dealer).

It is probably something relatively simple, but finding exactly what (pump failed, valve stuck open or closed etc) isn't going to be easy, and replacement parts probably only available from honda...

[keithr]

I suspect the battery heater is not contained within the battery pack, and instead a single heater controls the coolant used for interior and battery and a pump/valves divert as necessary.

Based on this diagram I copied from a Chinese publication over three years ago, the heating and cooling is shared for the battery pack, charger and DC/DC converter (it's a low resolution picture):

[Deleted User 473]

Silly question, but why is it thought that checking fuses or detaching the 12V would have any impact on a problem that the dash says is affecting the HV system?

Missed this in my last reply. The HV system doesn't power anything. Everything in the car pretty much runs of the 12v and supplanted by the HV dc-dc convertor (but only when the car is on / alive). When you have a flat 12v battery, the car is essentially a brick/potato. you wont be able to turn it on.

By detaching the 12v battery, you are in essence restarting all the systems/modules, a reboot if you will. The age old 'turn it off and on again' - working in IT ironically teaches you that that is almost always the first thing to try (despite the natural desire to want to understand and fault find, it really is the first stage to logical testing of anything).

As an example, there is a glitch in the inbuilt Garmin satnav software where you will lose voice instructions, the only fix is to either restart the infotainment by pulling the respective 12v fuse, or pull the 12v battery terminal. There is no way to 'restart' the infotainment module from the screens itself (as far as we can find, other than a full factory reset which forces a restart naturally). That's just an example. It may not help in this case, but there is no real way to know which modules retain temporary variables in memory when the car is 'off'.

[Deleted User 473]

I suspect the battery heater is not contained within the battery pack, and instead a single heater controls the coolant used for interior and battery and a pump/valves divert as necessary.

Based on this diagram I copied from a Chinese publication over three years ago, the heating and cooling is shared for the battery pack, charger and DC/DC converter (it's a low resolution picture):

Nice picture!

RAD = Radiator
CTS = coolant temp sensor
EWP = electric water pump
EWV1 and 2 = electronic water valve (I'm guessing). I suspect these will be a simple 12v solenoid type diverter valves.
EWH - electric water heater ) the block diagram shows it as close to the battery, but I suspect its under the bonnet somewhere.

Interesting to note that the Charging and DC-DC converter are the biggest inefficiency items giving off a few hundred watts of heat each. Its surprising the battery is only listed as giving off 400w, I had suspected more...

What is the ambient temperature where you are green1?

[green1]

I wouldn't post the pictures on here, as much as we would like to see them.

I suspect the battery heater is not contained within the battery pack, and instead a single heater controls the coolant used for interior and battery and a pump/valves divert as necessary.

Without a bit more detailed understanding, i'd say it would be hard to track down the cause in a reasonable time frame. I assume the coolant level under the bonnet is OK? No visible leaks? Its still worth doing the 12v reset if you haven't already (although maybe hold off on this if you are taking it to the dealer).

It is probably something relatively simple, but finding exactly what (pump failed, valve stuck open or closed etc) isn't going to be easy, and replacement parts probably only available from honda...

Hi EEEE, sorry about the late reply.

I didn't see any leaks and the levels looked okay. Thanks also for explaining the role of the 12V here, it's great to know that as a first resort I can effectively IT Crowd style turn it off and on again in the future. Edit: Did I understand you correctly when you said that everything runs directly off the 12V, that is, even the cooling system for the HV itself runs off the 12V, i.e. the HV only powers the traction motor and charges the 12V, and nothing else?

Also what I said about the error not showing up in at night was inaccurate, it almost always showed up, just a little bit later than it did during the day time, perhaps just my mind seeking a pattern. I'm in London by the way, it's just a been a hot week recently as the summer kicks off. In either instance, the performance/acceleration of the car seemed to be entirely unaffected by the warning and it seems to run nominally.

I took the car into my Honda dealer's workshop today. I was there for about two hours, with the works being completed in about an hour and a half. I don't have the service sheet in front of me, but off the top of my head as I understand it they did three things in the following order, they ran some tests on the heat exchanger and coolant loop to verify it was working as per spec, and they also said that the dash warning / error was being caused by a software glitch for which Honda has quite recently pushed a software update, and they've pushed that update to my car. Lastly, they cleared the fault codes via OBD. To avoid having to drive it back/forth (it's about 40 miles from me) I mentioned I was willing to leave the car for a couple days, even a week or more, if there was any doubt, but they were absolutely sure that the problem is fully resolved. So I drove the car back and all seems good. All in all I'm happy and I do believe the issue is resolved, fingers crossed.

[Deleted User 473]

i believe nearly everything runs off the 12v system. almost certainly the coolant pumps and the valves etc. not sure on the water heater. it could be 12v but supplanted by the dc to dc converter. when the 12v goes flat, the car is locked out of itself effectively. no power to energise the systems and close the HV contactor/isolator and get the dc-dc converter up and running.

you can quite quickly drain the 12v if you are not careful, especially if your 12v is a bit lame.

interesting that the dealer mentioned its a software glitch, not one anyone else has reported. the software of course residing in the modules and controllers, and nothing to do with the infotainment and the single update for that that has been pushed out.