I pulled up the code poo37 and i seen that it said O2 Sensor 1/2 Heater Circuit Low so... how do i go about fixin it

 

Turn the ignition off.
Disconnect the O2 Sensor harness connector.
Measure the resistance of the O2 Heater element at the O2 Sensor connector
(component side).
NOTE: O2 Heater Element resistance values should be measured at 70°F
(21.1°C). The resistance value will vary with different temperature values.
Is the resistance of the O2 Sensor Heater Element between 2.0 and 30.0 ohms?

If not, replace it.

It would help if you told us what year engine is your truck.

 

99% of the time, it means the heater in the 02 sensor is bad. But test it as mentioned above.

 

I dont understand how to check it..so what o2 should i get there is four of them or is all them the same?it's a 2004 5.7L 4x4
thanks for your help...

 

Are you sure that code was not P0137. 1/2 means drivers side downstream O2 sensor...
See pic attached, should be #4 in the pic...

 

I went out an checked again POO37... is that any certain one?

 

i fixed it it was where i put my headers on and the 02 was touching the cat on it melted all the wires i got them all put back an got them zip tied up..