Hi. I watch Alex's videos on YouTube all the time, trying to learn more about repairs. But I know when I've met my match.

I don't know if you can help me, or if it's a lost cause and I should just give up trying to repair.

I have a key fob for a Toyota Prius 2005 (Australian left-hand-drive model NHW20R) that went through a washing machine cycle and stopped working. To buy a replacement and enrol it with my car will cost $500 (Australian dollars) from an auto locksmith, or $1000 from a Toyota dealer, so I'm happy to pay good money (and shipping from Australia) for a likely repair.

The symptoms are: Button cell goes flat quickly even when not used. When I press the buttons, nothing happens, light doesn't flash. When I give it 3V from my benchtop PSU, it pulls this down to about 1.2V and draws 800mA. I figure there's a short, but I can't find it.

The fob has two chips on it with labels that don't show up in Google searches. Both chips are getting very hot, sprayed IPA dries very quickly. No caps are showing 0 ohms. Two caps are showing 50 ohms in both directions and not reversing polarity, I figure it could be a resistor in parallel inside one of the chips. There is one resistor connecting +3V to antenna that is showing 0 ohms, but I don't think is likely to be causing so much power drain when not connected to ground.

My fob model code is B31EA (I think Toyota part number 89904-47020), which is identical to B32EG but without the third button (opposite end to antenna) installed, only empty pads. The B32EG model has some info at the FCC ID website: https://fccid.io/MOZB31EG/Internal-Photos/Internal-Photos-310388. Unfortunately the schematic and parts list are not provided on FCC ID website due to confidentiality request by the manufacturer.

I don't know if either of the chips store the fob's unique code, or if they are all the same between fobs and can be substituted. Inside the fob is a separate transponder device which looks like 4D67: https://www.thekeyguys.com.au/transponder-chip-toyota. This might be the only part that is unique, but I don't know enough about these.

I've seen you fix fobs on your YouTube videos. Do you think you can fix mine?

Cheers, Jeremy