08 hch original owner
Dealer installed warranty "reconditioned" IMA battery and "required " system reflash. Approximately 2016.
About 4yrs ago I would get one P1575 code every year almost like clock work.
This year right on schedule P1575! Except now it intermittently throws it within weeks after resetting. So seems like whatever is failing is getting worse.
I had the 2yr old 12v battery tested at Autozone and Orally both tested good.
I don't have a high $ scan tool but my code reader does do freeze data and live data.
So far the freeze data shows codes set at 0mph and 0-2rpm.
This may be a clue but I need some guidance: the Live Data with no codes and engine off or on shows very erratic voltage pattern. See attached. Also the rpm signal is similar pattern. I have more pictures but not sure how to attach. Will send in a 2nd post. Thanks.

 

Here's my other irregular live data captures (I hope)

Not sure this is a vehicle issue or a tool issue? It sure looks like some kind of electrical interference. The only modification or accessories is the digital voltage meter/USB charger in the acc socket at the top of photos (which I calibrated with a calibrated Fluke DVM and it reads a noticeable bit higher than the live data engine off!) And also a dealership installed theft protection which I declined to activate.

I tried to get live voltage off my 01Tacoma to see if it's the tool but it's not shown. Maybe I can get a friend to allow me to plug into a vehicle that shows voltage. Maybe I'm not even chasing the right symptom?

 

Drove Civic today approximately 25mi some hiway, some surface streets with live data on.Several autostops and Several lengthy stop to shop and restarting . No codes. The voltage graph would occasionally settle down but not for very long. I did remove the digital voltage meter to eliminate any effects that it may have.
I understand the DC o DC
converter meters the charge to the 12v battery and the electronic 'switching may explain the pulses while engine is running but not with engine off??
I'm thinking about checking the 12vdc output connections at the converter? I already checked and cleaned the battery terminals.

 

There may be codes your reader can't detect.

Blink the codes:

https://99mpg.com/mikestips/readingtheblinkcod/

The codes listed are not for your vehicle.

A P1575 is 1 long and 2 short. You need to count them on both the IMA light and the check engine light.

P1575 has 55 steps to the troubleshooting tree, but only if it is the ONLY code.

 

Great, thanks. This blink code should get me started in the right direction.
Oh, I put my reader on a F250 and the voltage tracing was just as erratic so I'm going to ignore that.

 

Consumer grade code readers fall short on hybrids.

When you get the blinks, let me know.