Would 12v Battery cause false check engine light to come on?

1. If you have any doubt about the 12V battery then you should replace it now.

2. Classic Prius did not have perfect hybrid powertrain control logic. If you only notice this shuddering in the first 10 minutes, that's not bad.

3. It does appear that your car may have some latent problems with the inverter and transaxle. After you have taken care of #1, if your car still logs DTC then I suggest you have the DTC and three digit info codes read by your local Toyota dealer and ask for their diagnosis, to see if you get a different opinion vs. the repair invoices you cited in your OP. Good luck.

 

I just bought a 2008 Prius with 19,000 miles, no service history. The trip home was about 150 miles. After about 100 miles, the big red triangle and 4 other lights suddenly appeared and the cruise control quit. I pulled into a rest area, waited about 15 min and checked the oil level. Proper level and clean. Figured at least I wasn't gonna burn up the engine. Started up and now only the red triangle and check engine lights were on.
Had local Toyota dealer check computer history and no fault codes present.
Started to be difficult to start. I decided to check battery votage, only 10 V after sitting all night and the interior light was also dim. This 12 V battery was also black Toyota battery. Replace it with a Yellow Top from Advance auto and no problems since. It is interesting that the Toyota service peope never suggested replacing the battery. That is the great advantage of this forum.
Dennis

 

For the record, a very good replacement battery for this car is available from Toyota since October 2003 when they superseded the original battery.

Because the dimensions and posts are different, so you don't have to jury-rig anything they sell an inexpensive retrofit kit leaving you a safe installation that looks completely stock (and is, in the sense that this is now the stock Classic battery).

For part numbers follow the link above.

-Chap

 

NinnJinn,
I have noticed that on the Gen I's, if you put the shifter in gear (D or R) before the engine starts, it will cause a Triangle and Check Engine light. I never read the codes when this happened to me but, the sypmtoms are the same as you mention.

Putting the car in gear too quickly (before the engine starts) sometimes puts the car in Outofgas mode (which in turn triggers DTC's). I would be willing to bet this is what happened. The fix is to "slow down" and wait for the engine to start b4 putting it in gear.

 

I will share my experiences with my own 2002 Prius which has 115000 miles. Bought the car 4 years ago. 2 years ago we discovered we could not park the car more than 3 days without the 12v battery going dead. It was the original battery! The original battery in the 1st gen Prius resembles a motorcycle battery and according to Toyota an upgrade kit was made available because the original battery "had disappointing performance". In other words I could not get them to admit the battery was insufficient for the car. So anyway the dealer installed the upgrade kit and a new larger battery for $200.oo which they claim "should be good to park for about 10 days".
there is a way to check the 12v battery voltage with the onboard system check mode on the touch screen. What you describe, small black battery with Jap writing sounds like the original.
AS to the "triangle of death" we are very familiar with it. Apparently the early years were plagued by defective wiring harness on the main battery. According to our cars' service history the original wiring harness was replaced back in 2005, along with a recalled power steering unit. Even so it remains very sensitive, especially if you "bump" the wiring harness area (in the left front corner of the trunk) with cargo. Most recently we received the "triangle of death" award for parking on an uneven parking space with the front wheels turned hard to the right. Dealer still insists it's nothing. It never happens when I drive the car, just the wife...

 

Having a recorded P3125 with INF 287 points to a service bulletin for the HV ECU, EG021-02.

2001 Prius: DTC..about 2 mph with a whine before it..faulty - JustAnswer