2000 echo check engine light

[shuetming]

Hi, I am driving a 2000 Toyota Echo and i bought it 1 year ago. when I first bought it, right after I drove off the dealer in about 10 minutes and the engine check light was on. I went to Auto Zone right after and they checked it was a problem of the O2 sensor with the code PO141. I replace the sensor 2 months later, but it went back on after I pick up my car at the shop. They told me the other one is malfunction too, so I went and replace the 2 second too. But after that the code was popped up again..Since then I never really change anything of my car..But I keep checking see if the code has changed or not. I went to auto Zone and checked today and it's still PO141 this code. Which is different then everyone in this post. Could you help me to see what is wrong with my car? thank you very much!!

[mustang67408]

First off, you need to check the voltages going to the O2 sensor heater circuit. If you do not have the proper voltage then the ECU is probably bad (or the wrong one) or you have a problem in the wire harness to the sensor.
The next thing is to check the ground side of the circuit. That sensor has a connector behind the glove box that also goes to the ecu for the ground, or there may be a problem in the wire harness.

P0141 is for the REAR (behind the cat) sensor not the front one.

I hope you used a TOYOTA sensor not an aftermarket. The Toyota sensors are just as inexpensive as the aftermarket ones.
see attachments for help diagnosing.

[shuetming]

sorry I know it sounds stupid but what is ECU and wire harmless? I am not very good at electrical stuffs..

Thanks.

[mustang67408]

ECU = Engine control unit or the computer that runs everything

Wireharness= all the wiring in between the 02 sensor and the ECU.
If your not so good at electrical, you should get some help from someone who is, and most of the people at AUTO ZONE and places like that are not that good.