so when my truck has just been sitting for a little while at idle the cel comes on and it throws this code

P0158 (M) 2/2 O2 Sensor Shorted To Voltage Oxygen sensor input voltage maintained above normal operating range

occasionally it'll idle roughly..

is this because of the code? also what has to be done to fix this

 

Sounds like some sort of serge to your O2 sensor. If they weren't $70 I would say just replace it and see what happens.

 

4wire 02 sensors have a heater circuit to get them warmed up quick.
the HEATER side is 12v the other side is the computers 5v.
IF the heater side shorts to 5v referance then this code may set...often 4wheeling damages the sensor or wiring....look at the sensor and first foot or so of the harness.... damaged melted often a visual will spot it...

other considerations....
no other codes?
Vehicle IS STOCK?
would be good to see what the o2 sensor is telling computer...lean=lowvoltage, rich=hi voltage...

 

I agree to check the O2 sensor, but this is the rear sensor and should not affect how the engine runs.

 

thank you I will be checking it pretty soon here

 

My Dak was throwing a P0420 which is catylitic or oxygen sensor issues ,so i got the two oxygen sensors replaced and now my idle and gas mileage has improved,but before you spend the money i tried something else that was recomended first,a container of fuel injector/carbuerator cleaner for $3.00.That shut off my check engine light and improved fuel and idle temporaraly after about three start ups.The link for the best oxygen sensors is here http://www.ngk.com/default.asp good luck with your situation bro.

 

Keep in mind O2 sensors are wear items and should be periodically replaced even when your PCM is not throwing a code, ideally.