Wireless Key Lock/Unlock Intermittent

My key fob which remorely unlocks/locks the doors worked intermittently.

I purchased a new replacement key fob and had the car programmed to accept it. Still worked intermittantly.

So i ruled out the key. Must be the car.

I replaced the "Receiver Assy, Door Control & TPMS." Now the tire pressure alert light stays on, and the key doesn't work.

I'm guessing there's some programming needs to be done to match up the replacement receiver with the car. My mechanic said he couldn't do it, I'd have to go to a Toyota dealer to have it done.

I'm worried Toyota dealer will charge many hundreds of dollars, more than is worth the trouble.

Is there a way I can program it myself?

Or, maybe I should put the original receiver back and see if i can fix it. I'd need a schematic of the device, or at least some information about the 12 pin plug. Seems like a lot of pins when I only have 4 tires and one key.

Is there some electrical information available? (I'm an engineer familiar with electronics. It's just really hard to fix an intermittent problem without a schematic.)