Some diagnostic trouble codes (DTC) have 2-trip detection logic. That means that the electronic control module (ECM) has to see the same trouble on 2 consecutive "trips" before illuminating the malfunction indicator light (MIL), commonly referred to as the check engine light. There is a specific definition of a "trip," where certain parameters must be met, like coolant temperature, engine speed, road speed, distance traveled, etc.
A pending code means that the ECM has counted the fault on 1 trip and if it sees the fault on the next trip, it will illuminate the MIL and store a fault.
P0105 means that there is a problem with the manifold absolute pressure (MAP) sensor circuit. That can be a problem with the MAP sensor itself or the related wiring. The MAP sensor is located on the outlet side of the air filter housing. If you look at the air filter housing, it is the only electronic device on the housing. If the air filter was recently checked or replaced, make sure that the wiring connector for the MAP sensor is snug. If the MAP sensor is snug, then you can try cleaning the MAP sensor. The MAP sensor is not supposed to be serviceable, but IMO, it doesn't hurt to try cleaning it since you would have to replace it anyway if it is bad. The MAP sensor has a heated wire inside, and as air flows past it, it cools the wire. As the wire cools, the voltage passing through it goes up, and the ECM can tell how much air is flowing past. If the wire becomes coated with dirt or debris, it acts as an insulator and the air flowing past does not cool the wire, trigging a DTC. Remove the bolts that hold the MAP sensor in place. You will see a tube that protrudes into the airstream coming out of the air filter housing, and the tube sometimes gets clogged with an oily residue or dirt. Gently spray some carburetor cleaner into the tube, gently shake it out, and after it dries, replace the MAP sensor. If that doesn't work, refer to the Camry repair manual for testing procedures..
P0401 means that insufficient EGR flow was detected. The Exhaust Gas Recirculation (EGR) valve allows some exhaust gas to enter the combustion chamber to lower combustion temperatures and reduce NOX emissions. In high mileage cars, it is not uncommon for the EGR valve to become clogged with carbon deposits, reducing the flow of exhaust gas into the combustion chambers. If you remove the EGR valve, you may be able to dig out some of the carbon deposits with an awl or screwdriver and wash some of the stuff out with carburetor cleaner and prolong the EGR valve's life a little.
Here is a link to the factory service manuals for Camrys: