Intermittent Red Triangle - not diagnosable ...

Hi All,

I'm new to the PRIUSchat, and I'm hoping someone here might have an idea what is wrong with my car. I am running out of money and patience.

Background:
My Prius has ~220K miles on it, and it has generally been a reliable car, except for the stupid touch screen part of the Mult-Function Display (MFD) that gave out, and no one will help me replace it, even though I found an after-market replacement. But I digress ...'

The car burns very little oil. I have been using High Mileage Mobile 1 in it as long as I have had it (I'm the 2nd owner, bought it from a Toyota dealer when it had 150K on it). There don't appear to be any major leaks and the car runs pretty smoothly.

The car sat for a long time during the pandemic, and during that time someone stole the catalytic converter. Fun! I didn't realize that was a thing before then. My local mechanic, who is honest and very nice, but not a hybrid geek, replaced it with an after-market converter and put a cage on it for me. After he fixed it, the dash was still lighting up like a Christmas tree, and he said he wasn't sure why. He knows I am not flush, so I'm sure he didn't spend a ton of time on it.

The dash lights up like a Christmas tree, even though I've had many, many things fixed on it. The car is not worth fixing everything, I just want to get this damned triangle thing fixed.

The Triangle Issue:
So, this intermittent triangle thing started happening over a year ago. Yeah, I know, I should have gotten it fixed, but ... everybody thinks they know the problem, but no one can fix it.

The Symptoms:
At first, it seemed to be happening more often when I was doing highway driving in the rain. It does rain here once in a while, you know. A guy at an auto parts store, suggested it had to do with poor traction (I don't think he knew what he was talking about), but my tires were in pretty poor shape, so I decided it would be a good idea to replace them regardless. I replaced them with highly-rated Converse all-season tires. That didn't fix the problem, but it occurred to me that when I was doing that highway driving in the rain, I was also running the headlights, windshield wipers, radio and sometimes the defrost system. It gradually became more frequent, but it NEVER occurrs when the car is cold. It usually takes at least 10 minutes of hard driving (hills or highway and running the AC in the summer is a sure way to make it happen). So for short trips it's fine, although I can't run the AC when it's sweltering hot, even though the AC works. The heating system in the car isn't great, but I think (I haven't done a thorough test yet), that blasting the heat while driving may help, but I'm really not sure about that.

Now if I only needed that car for around town, I could probably live with this, but usually drive out to see child who lives about 100 miles away, at least every 2-3 months. I have to cross a mountain pass, and the combination of the hills and the highway driving makes the triangle thing go on like crazy, even without running the AC in the heat. I really don't want to have to take the bus every time I visit. Also I sometimes have to do some driving for work, and a frequently see the red triangle then, too, although the drives are much shorter.

Things I have done since that occurred:
12 volt Battery
Tires (good all-season)
12 volt Battery
Hybrid battery repair - CPU replaced)
Spark Plugs and Ignition Coils (recent)
Oxygen Sensor (recent)
Hybrid battery diagnostic (recent - functioning fine for its age)
Other diagnostics, including one from a Toyota specialist
And of course the usual stuff like fluid changes, wipers, etc.

Most recently, I took it to a shop with a good reputation, that has worked on quite a few Gen 2s and had all
the Toyota diagnostic software for the hybrid battery system. I had a discussion with him before I brought it in, and he seemed quite confident he could find the problem. Well, he didn't!

Like all the previous mechanics, he told me what he thought was wrong, and I told him why. He told me the ABS module was faulty, and that my front brakes needed to be replaced. He said he checked the hybrid inverter cooling system, including the pump and fan, and that they were working fine.

I don't doubt that my front brakes should be replaced, even though the brakes seem to work fine, since it has been a long time since the brakes were done. But I'll be damned if I'm spending $1500 plus labor for an ABS module, on this car, especially with the Triangle problem. (Fixing the ABS brake module is likely to break me!) I explained to him that the intermittent red triangle problem NEVER occurs when I am braking. It typically occurs while high speed driving, while running the Air condition, and when accelerating (especially on an incline) - running accessories (especially the AC) seem to make it occur more frequently. He told me he had to follow the procedures outlined by Toyota. He also wasn't able to reproduce the problem, which is not surprising, since he didn't take it out on the highway. I offered to take it out for a spin on the highway, and bring it back with the issue, but he reiterated the bit about following the recommended procedure. I might have him replace the front brakes, since that's a safety issue, but I don't want to sink more and more money into stuff that won't fix my red triangle problem

So, do any of you have an idea what might be going on and/or where I should take it? I am reluctant to take it to a Toyota dealer, since they would likely run the same diagnostics as the Toyota specialist I saw. Whatever is happening with the car is not showing up on the diagnostics. I really want to find someone who is able to diagnose it even though the codes are not really telling what is going on when that red triangle comes on. It really needs to be someone who is intimately familiar with older Priuses. The mechanics I have taken it to were all pretty experienced.

 

I forgot to mention, that the triangle light will go off pretty quickly if I go on an extended coast (when I am not pressing the accelerator), as long as I am not running the AC, but when I am doing extended highway driving, especially in the summer, I periodically have to stop and let the car cool down for about 5 minutes. The cooling systems seem to be OK, and the temperature light never goes on.