I recently got the service engine light on my 2003 Honda accord 4cyl which has 80k miles on it. The displayed code is P0141 which refers to the downstream O2 sensor. By downstream I understand that it is the o2 sensor post cat. I guess I can start my replacing the O2 sensor but I wanted to know first if it a common issue with the Accord. Does that mean I have a problem with my cat converter or is it just a matter of replacing the O2 sensor?
Thanks for any info you guys may give me on this

 

That's specifically for the pre-heater for that sensor. So it's not really a bad signal from the sensor, and shouldn't be anything wrong with the cat itself.

To unplug the sensor, I think you might have to go under the right-front seat & peel back some carpeting. Look for 2 same-color (black?) wires going to the sensor (not the wiring harness). Get your multi-meter & measure resistance between them. I think it should be 10 to 40 ohms, but usually a failed heater will be open-circuit.

If the heater resistance is OK, measure voltage across the corresponding wires coming from the harness. Key on, they should have battery voltage between them.

 

Thanks Jim. Yes I found out that the sensor wire goes through an opening in the floor under the seat. Is the preheater a separate component from the sensor itself?

 

No, it's electrically separate but physically built in. If the heater is open, you need the whole sensor.

When you're testing, the 2 heater leads (to the sensor) should have resistance between the 2, but they should have NO continuity to ground.