06 Prius with C1554 Error Code

Hello friends, my prius was driving fine the other day and then the steering assist totally died randomly. After scanning it today it's shown code C1554, which from what I could gather from the scanner, seemed to be pointing towards the electric steering assist motor no longer functioning. However, from further research, many people seem to go straight for the steering ECU (under top panel of the dash?). I have the PS warning letters on my MDF screen. I thought it was weird for the PS ECU to be dead if the diagnostic systems all seemed to respond well showing input and output voltage and currents.

All my input torque voltages seemed to be responding fine, but all zeros on the output front. Has anyone had the same issue and can help me? Mine is a right hand drive car if that matters.

Thanks!

 

Looks like time to get another PS ECU. Thanks so much for clearing that up ChapmanF!!!

Mine has 289,XXXKm on it.

No idea at all why it failed, I assume just normal relay failure after so many tens/hundreds of thousands of duty cycles.

I often do turn lock to lock when the car was functioning as normal, but since the failure I have not. It should be able to, just very heavy on the steering input required.

 

Just an update, all fixed with a new (second hand) PS ECU

For anyone interested about the internals, I donated my old one to my tools in the name of science

 

For anyone wondering, the Omron g8se-1a4 225ohm relays used are pretty available aftermarket, looks super annoying but doable to replace the relay on the PCB. Might have to become a common solution once these cars are a bit older.