I've had a CEL code 1001 (front left O2 sensor) that I reset and it came back about a month later. Both times the light came on when I started the car

I checked the resistance between terminals 1 and 3 and the resistance was 4.4 or 4.5. According to the stickies (for code 0901 which is for the front right O2 sensor), if the resistance wasn't too far out of normal operating range (2.3 - 4.3) then the sensor should be fine. Although it does say if I get code 1001 that the sensor is bad.

Is the heater bad or is it the sensor?

The car has 201K miles and the sensor has never been replaced. Should I replace the sensor anyway since it's old?

 

some o2 sensors have heaters some don't. the my 97 fed spec uses 2 three wire bosch heated sensors pre cat. and one after the cat in the b-pipe.( i believe this is a 4wire one)

my max has 180k miles with orig. 02 sensors
just did the front left sensor b/c i got various codes related to it (P0150 twice and P0174 once).

Clearing the code without solving the cause will not get you anywhere.

it's a pretty easy job but you need some good penetrating spray and a 02 socket wrench.

mine was extra stubborn so i ended up using a torch to get it loose.

remember to pre wind the o2 sensor wire before installation.

 

3 and 4 wire o2 sensors are heated.
it doesn't hurt to replace a 200k o2 sensor since even if it isn't bad, more than likely it is sluggish in it's response which can hurt gas mileage.

 

o i have the same problem, second time i got the code 1001, changed the o2 sensor nov.09

 

i'f there are no other codes,I would change the 02 sensor.

 

ok ive got 180k on my 4g i got a scan tool and got the front o2 code changed it for a universal 3 wire, did the work, bought a o2 remover changed it, use my scan tool got rid of the code...did fine the CEL never came on and checkt the codes again a week later just for fun and i had the code again..deleted it and checkt it again 2 days later and there it was deleted it again and never came back....
mistery remains unsolved