o2 sensor issues
 

i have an 01 supercrew and starting last winter when its below 10 or 20 degrees and the truck isnt plugged in the front o2 sensors dont switch into closed loop mode and cel comes on and the truck burns a whole bunch of gas. any ideas where i should start looking to fix this problem?

Start by replacing the thermostat - and use a stock 192 (I think). Check the fan clutch, it may be locked up and running all the time.

You should start by reading the fault codes so we know why the MIL is coming on...

Do this before ever picking up a wrench.

well, the codes i was getting last winter were p1152 and p1158 the code i got the other day was just the p1152 this time. and 1152 is "Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Rich - Bank No. 2" and the p1158 is "Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Rich - Bank No. 1"

the thermostat i have is one i put in summer before last and as far as i know it works just fine, and the fan runs all the time, but is sometimes off for a few minutes when i start it cold

Run MAF diagnostics. - since the PCM uses the MAF to determine airflow for fueling, idle (with IAC). Any symptoms ? Hows the trucks power/ shift points ?

the truck runs and drives great. the only other issue ive had with this truck is that when you rev it up in park or neutral it comes back down to idle slower than others that ive seen. how do i run maf diagnostics?

should i go ahead and put a new maf in my truck? cause ive already cleaned it once, and ive been told by more than one person that the maf going bad can cause these o2 sensor issues ive been having, and its only in the winter that i have these problems in temps below 20 degrees.

Those DTC's are on the same Bank, -Bank 2 Drivers side.

P1152 Lack Of HO2S21 Switch - Sensor Indicates Rich

P1158 Lack Of HO2S22 Switch - Sensor Indicates Rich

Possible Causes:

#1. Pinched, shorted, and corroded wiring and pins.
#2. Crossed sensor wires.
#3. Exhaust leaks.
#4. Contaminated or damaged sensor.

Well last winter I kept getting codes for both upstream sensors and one of the service guys at a local dealer said it could be the maf causing the o2 sensor switching problem. And I'm thinkin about throwing a new maf in the truck and seein where it goes from there

Do you use a dry or oiled air filter (such as a K&N)? If it's oiled, the oil is known for fouling the MAF.

i use a k&n filter, but last winter was the first time ive ever had any real problems with this truck, and ive already cleaned the maf once or twice