Red Triangle, OBD does not work

A month or so ago, when the temp went down to -25F degrees, my 2008 gen 2 decided not to cooperate in getting my wife home. Lots of lights lit up (CEL, red traiangle, etc.), the ICE would chug heavily but not start.

It sat for a week or so and once the polar vortex passed, it was found that the 12v was low, so I had a local mechanic put a new battery in for her. Anyway, in the end, the ICE now starts, the car drives (we drove it an hour home), the hybrid battery shows it is charging when driving, even up to one bar less than the top. BUT... red triangle light, car image,with red triangle light on display are o. All the rest of the lights turn off once started. But the OBD seems to be without power. OBD fuse #8 checks okay. But it won't light up any of my scanners, or put a light on my Bluetooth OBD2 variant. So, I cant pull codes.

Before the failure, fuel economy was reduced, but as it was winter, we thought it was driving differences (and it might have been).

So, its in some sort of limp mode, and I don't know how to proceed. Anyone have an informed idea as to what might be going on and how to proceed in getting the OBD working? (What, other than the fuse would render it inoperative?)

 

Thanks, Patrick,

Double checking the basics as you described, caused me to realize I was actually looking at the 7.5a on the wrong side of the fuse block. (Something about looking at things upside down while having pain induced on your spine.) And I am a multi-decade computer IT specialist.

The fuse was indeed blown, and once replaced, everything lit up and worked. So, what was found? The code pulled was for an emissions o2 sensor, cat insufficiency error code P0429. Possibly a sensor, or possibly the cat (300K mi?) Of course, everything shows OK now, so its not entirely non functional. The hybrid battery looks fine with all cells close to one another. (Oh yeah, baby!)

So, hows this for a working theory? Very low temps put the 12v battery over in low voltage, causing things to run really badly. Once it was replaced, the cat oxygen sensor thing caused a triangle flag. (Is this normal?) But no CEL, or other lights. As Greg was already paranoid due to reports of the chugging of the ICE under low 12v battery voltage, he assumed the worst, especially when the OBD port was found to also be dead. But there was another person that worked on the car (12v battery install) that may have promoted the OBD fuse blowing. A wildcard variable!

Techie Greg, looking upside down under the dash (and, from childhood, never being good at Twister), pulled the wrong fuse, which was, of course, fine. Patrick tells Greg, in essence, "check the basics!", which he did, realizing immediately his tragic folly and mistake. In the end, Dogs and Cats start living in unified harmony and Wesley and Buttercup get together, have amazing kids (that also are not left handed) and grow older, wiser and somewhat fatter together.

In the end, the foreboding Red Triangle of Death was more of a Red Triangle of Irritation, as it was thrown by a Cat insufficiency code on a 300K car.

But that's, of course, only a theoretical view of things. And besides, there are problems with that scenario, as we all know that Buttercup, having inherited perfect genes, would almost certainly retain her ideal BMI as she aged.

Thanks for the help!

 

Sorry, you are correct. Keystroke error. P0420. And no, the CEL was not on. (It was when the 12v was low, along with everything else). I thought it was strange. Once I cleared the (single) code, the red triangle went away and has not come back yet. (200mi thus far in town and hwy)

I was not aware that this forum was also focused on marriage advice and husbandry correction. Nice bonus. Glad you care.. I've been happily, and successfully married for 30 years. The 2008 Prius is not our only car. But it is one of her choices of vehicles to take for her all highway, no rush hour commute, and it presently runs snow oriented treads, not low rolling resistance. Though not a good deep snow car, due to its low air dam, it is a surprisingly capable winter driver on maintained roads with the right tires (and experienced winter drivers). We tend to drive, and winter-specific equip our older stuff for use in the (real) winter as such driving conditions take a heavy toll on car chassis. Our choice.

In this car's defense, the rare -25F temp resulted in about a third of the cars in the area becoming un-startable that morning and made for a windfall for all stores stocking auto batteries over the next few days. Of course a Prius often does not exhibit typical symptoms when its 12V battery is low as it is so computer-centric. It turned the ICE over just fine (off the traction battery) but the ICE would not run normally (still low voltage to computer, sensors and likely ignition). I don't know if you have life experience in those temperatures, but it is hard for any engine to start if not running a block heater (which is not a common thing here, except for things like commercial maintenance vehicles). But that would not have helped in this case. It is also possible that the Cat flag came about due to it being temporarily loaded with unburned fuel residue from the ICE previously trying to start under low voltage and not successfully doing so.