P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

My son has a 98 Escort GT. 2.0, the check engine light has been on
for a while with the code P0141 02 Sensor Heater Circuit Malfunction
(Bank 1 Sensor 2), but the car still ran ok. Just recently the car
started fine and he drove about 1/4 mile and the engine quit, it would
not accelerate. Once the car cooled off it would start again and do
the same thing. I checked the codes again and an additional code was
there (PO136), which was the 1st o2 sensor. I changed the 1st sensor
and the code went away, but the car still has the same problem it
shuts off after a 1/4 mile or so, the 2nd code is still there. If I
change the 2nd sensor will this fix the problem or could something
else be causing the car to stop?