New 12V battery: car won't start

Problem is I cannot connect to the car via OBD, so no way to check for any codes.

 

There is no AM2 fuse under the hood in my (mainland) European version, could have been below the steering wheel but I checked them all and they were fine. But will check again to make sure.

Yes same voltage as directly on the battery, also headlights and horn work fine. Only thing on the dashboard (HUD) is the door-open symbol if I leave a door open. Cannot get anything else to work, no ACC, IG-ON or READY mode possible.

 

I may have narrowed the problem down a bit more. My sister owns a 2008 Prius (also 2nd gen) and she visited me this evening so a nice opportunity to compare both cars. First of all I noticed that in my car the immobilizer indicator does not blink every second or so, it should even with the car doors locked. Maybe I never noticed this before because I worked on it during the day time. Everything else seems to work as it should. When I enter the car the green leds on either side of the keyfob slot are lit. After about 15-20 seconds these green lights dim but when I slide the fob in the slot the Power button lights up faintly, just as it should.
So the only difference between both cars is my immobilizer light not blinking, it is possible that this is the cause of the defect. Does anyone know if the immobilizer is a separate part or if it is integrated within the ECU?

To be clear: my manual is in Dutch but with 'immobilizer light' I mean the symbol of a car with a key in it on the HUD. Hope I got that right.

The Netherlands has a moderate sea climate and I am about 20 miles away from the sea but drive close to it on occasion, it's almost impossible to avoid water and moist over here. It also rained a lot the last couple of months, much more than usual. And it could be the cause of corrosion in a connector.

None whatsoever.

 

The layout of my fuse box looks slightly different but the one on the right second from the top (#9) is labeled IGN, which is probably the same as AM2 in the US version. It was not blown, none of them were. The fusible link was also still connected from top to bottom on both metal strips.

 

Yes I did, took the transparant plastic cover off and both metal strips connect from top to bottom. I don't think there has been a short anywhere. Most likely a bad connection. The indicator light of the immobilizer no longer flashes on the dash so I am trying to locate where the immobilizer ECU is located. Should be somewhere under the dash to the right of the steering wheel. But even the repair manual is not very clear about that.

Does anyone know the location of the Immobilizer ECU in a gen2 Prius? I expect a bad connection there. It looks like this and is sometimes called 'transponder module', a bit confusing.

 

If it is located just right of the steering wheel it would be very close to the radio which has intermitently stopped working in the past. That makes it plausible to try and find the cause in moist and corrosion in one of the connectors there. If I have the exact location of all components of the immobilizer and start system I could take the dash cover off next weekend.

 

Thanks SFO. I had seen this image but still don't know which part the immobilizer would be. Toyota simply calls it 'ECU Immobilizer' on the label of the part but does not mention this anywhere in their repair manual. I think it is called 'transponder module' in the manual but then I don't see that in the included images anywhere. Wish they had been a bit more clear about it.

P.S. Only thing that comes close is the 'Smart key ECU' in the image above. But it does not seem to be to the righ of the steering wheel, more like above. Maybe Transponder Module, ECU Immobilizer and Smart key ECU are all refering to the same part?

 

That could be it as well SFO, no idea. I intended to have a look behind the dashboard but it suddenly started freezing again in this part of the world, seems winter is not over yet. Waiting for the weather to get a bit warmer again. I will let you all know how it turned out, maybe take some pictures. Thanks!

 

Suddenly realized I had never reported back on how the problem was fixed, so here it goes. Mechanic friend replaced keyfob slot and Entry Key ECU but that did not solve the problem. Next thing he replaced was the Hybrid Vehicle Control ECU behind the glove compartment and that fixed the problem. Had to turn 2 fobs into one using supper glue: now I can use one fob for both opening the door and starting the car. The fact that the problem occurred right after replacing the 12V battery appears to be pure coincidence.
Had a lot of moisture build up in the car the last couple of years, water droplets on the inside of the windscreen, so it seems there must have been a short or rust forming somewhere. Now I put in some moisture absorbing beads in two containers which I replace frequently so the air inside stays dry.
Thanks for all your help and suggestion! Glad I can still happily drive around in my 2006 Prius, hope to be using it for at least another couple of years. Thread can be closed if desired.