Trouble Codes
 

Have a 2000 Tacoma with two troubel codes :
(1)P0125 insufficient coolant temp for closed loop fuel control, (2) P1135 A/F sensor heater circuit malfunction , Bank 1, sensor 1
Anyone know what these two codes indicate, where to look under the hood,and why they are related ?????
Thanaks for any help !
JA