P0401 indicates problems with EGR system... It might a simple one, for instance, you just need to clean EGR pipe and valve. Or it can be more expansive one like faulty EGR valve or EGR sensor. Which one you have impossible to answer without testing the car.
And you can use the professional Toyota tool to repair it, I think the Toyota it2 is a good tool for it.
Trouble code P0401 means: Exhaust Gas Recirculation Flow Insufficient Detected
Trouble code P0401 means: Exhaust Gas Recirculation Malfunction
Trouble code P0401 means: Exhaust Gas Recirculation Flow Insufficient Detected
Trouble code P0401 means:Exhaust gas recirculation flow insufficient detected
Trouble code P0401 means:Exhaust gas recirculation flow insufficient detected
Trouble code P0401 means:Exhaust gas recirculation flow insufficient detected
Trouble code P0401 means:Exhaust gas recirculation flow insufficient detected
Trouble code P0401 means:Exhaust gas recirculation flow insufficient detected
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Go to NAPA or AutoZone, they will tell you.