2006 Prius not responding to power button

I have a 2006 Prius with the common "intermittent dead cluster" problem. Recently the driver side stator burned out in the transaxle due to a stuck coolant valve. I had these issues fixed at the dealership, and after completing the repair and road testing the vehicle they called me to come pick it up.

When I got in the car, it did not respond to the power button. At that point the dash lights worked (or at least the "door ajar" light lit up when I had the driver door open.) I tried the power button a few times with and without the brake held, and I tried long-pressing the power button for sixty seconds - none of this yielded a response from the car.

The tech connected his laptop and said he "found a communication error between the immobilizer and the ECU". By this point the cluster lights didn't work, and he said the dead cluster could be causing the issue. This doesn't really make sense to me - the cluster was working at the point that the car first failed to respond. I disconnected the battery a few times until the cluster lights came back on and had him repeat the test, and he pulled the same codes. At this point it was 4:30 and the dealership was closing so I left the car there.

The following day, the car started up no problem for the tech. They repeated this a few times with no issues. But then this morning, it refused to start up the first time, but worked five minutes later after the tech went back into the dealership to get tools.

Does anybody have a guess what's going on? The dealership is focused on the cluster issue, which doesn't seem likely to me. I'd like to avoid paying dealer labor rates and for an OEM cluster gauge, particularly since I doubt it will actually fix the problem.

 

I understand the costs of getting the cluster replaced at the dealership. The thing I'm concerned about is that my car now intermittently doesn't start at ALL. Are you saying the cluster issue can cause that?

 

I don't recall the specific codes I pulled, but the text readout said generator failure. I was coming off the highway, there was a clunk, and the left side started grinding really bad along with a massive drop in power. I determined from googling the symptoms and code that it was most likely the stator, which the shop was able to confirm. While they were in there installing the replacement transaxle (which I got a decent deal on - a low-mileage part had just come out of a dead gen 2 at a different dealership) they found the stuck valve, which the tech says likely caused the failure in the first place.

OK, thanks. I'm starting to think the capacitor burst and leaked conductive fluid onto the circuitry, which could cause an intermittent failure. I'm going to bring the car home and break down the dash, and see if I'm right. If there's no visible leakage issue I'll probably swap for a pre-programmed eBay board to be safe, but if there's some schmutz on there I'll clean it off with isopropyl, solder a new cap, and put it back together.

 

I've been driving this '06 since 2020 with a similarly highly intermittent cluster and it's always started. That's why I was skeptical this was the issue! But after looking at some electronic schematics it does appear a lot of relevant wiring runs through the cluster board, including the immobilizer, so I've ordered a replacement cluster with a programmed odometer to be safe.

The 12v is brand new and tested fine at the dealership after it failed to start. I unfortunately had to replace it before taking it to the dealership because after the stator blew, I foolishly left my OBD scanner plugged in under the dash while I took a different vehicle on a trip. By the time I got back I had drained the 12v so far that it was beyond saving.

And that's how I ended up with a new $220 AGM for a car that doesn't start. What a world.