No-start condition. Seems like 12V, but dealer tested 'good.'

Hello,

I am currently having an intermittent no-start condition - well no-READY condition - when pushing the power button, and I wanted to get your thoughts.

Just talking 12V battery in the below, not the hybrid battery.

Long story short: car has run fine and suddenly wont go into 'ready' mode, with no other issues or faults. The same thing happened in 2024, and when I researched the issue then, I found a post recommending to check the 12V battery. In that instance, the battery turned out to be bad, and I replaced it with genuine Toyota.

This time around I checked the the battery, and it was showing 11.7 volts, so I took it to the dealer. They tested it and said it was good - much to my surprise!

They gave me a little ticket that states the following:

------------------------------------------------------
GOOD BATTERY

Customer Complaint: Yes
Charging Required: Yep
Charging Completed: Oh yea
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Reserve Health: N/A

Cranking State of Health
----------------|---|-----------------
Replace_____________Good

(the formatting didnt come out great on this but its supposed to be a bar that shows the health state smack in-between Good and Replace)
------------------------------------------------------
Voltage: 12.85 V
Rated: 325 CCA
Measured: 339 CCA
Ah Replaced: 42.5 Ah
Time to Decision: 00:51:55
Charge Time: 01:36:12
Temperature: 77 F
------------------------------------------------------

This tells me that they had to charge it a fair bit to get it into normal range, and that after that the load test went well. Initially I was suspect that the DC converter wasnt charging the 12V battery properly, or that there was a parasitic drain.

When I got home, I put the battery back the in car, and it started normally - but a few moments later the red triangle came on. I plugged in the OBD reader and monitored voltages and temps. Everything seemed normal, also no fault codes, so I cleared the red triangle and drove around in the parking lot while keeping an eye on everything. The car drove normally and the inverter was delivering a rock-steady 14.0 volts to the 12V battery, so I drove on city streets for an hour. Everything seemed normal and the red triangle did not return. Hybrid battery was charging normally as well. I went home, parked, checked battery voltage, and then disconnected the battery from the rest of the car by unplugging the two positive harnesses at the battery - I wanted to check for parasitic drain. The battery was at 12.6V that evening, and the next morning, it was 12.4V. That seemed normal to me - to settle a little while resting, after being charged.

I plugged the positive battery harnesses back in, cranked it up, and it drove normally for the day. That was yesterday.

Well today I went to the grocery store, and on trying to leave, the 'no-start' condition came back. Checked voltage and the battery was showing 11.8V. Plugged in the jump starter and the car cranked. Drove home and monitored the inverter voltage while driving - it stayed at 14.0V the whole way. Parked and checked battery voltage again immediately - 12.0V resting, and when I try to put the car into 'Ready' mode, voltage drops to 11.3V!

My sense is that this is a 12V battery issue, but the dealer test is throwing me off.

What might I be missing?

- Ryan

 

Hello,

Thanks for your comments! I double checked the terminals, which were clean as-is, and hit them with a wire brush just to be sure; the problem still persisted in the same manner. I ended up putting my meter on the battery while 'starting,' and recorded the drops from 12.2v down to 11.3v for the dealer to see. The substantial drops didnt happen every time I tried to start the car, hence the intermittent issue, but when they did the car wouldn't go into ready mode. I took it to a different dealer this time. They did a more thorough test and confirmed that there was a bad cell in the battery.

Battery was replaced under warranty and now the car runs perfectly.

If you're reading this in the future and troubleshooting a similar issue, with a good suspicion that the 12v is at fault, I recommend asking the dealer to perform an in-depth analysis of the battery, and not just whether it meets voltage and CCA criteria at a single point in time.

Kind regards,
Ryan