'94 accord lx -- pulled my ecu codes, got #41. replaced the o2 sensor, reset the ecu, code came back on. i took a volt meter to the wires to test continuity. all good. with the key on(engine off) i'm getting 12 v to only ONE of the heater wires. are they both supposed to be hot?

 

Hi and welcome to the forum!

there are 2 codes with heated O2 sensors - just because there are 2 sensors

#1 O2 and #41 O2 heater make sure we're talking about the same one here

you didnt specify what kind of engine you have but my guess would be F22B2 coz you said it's LX model - so i believe there is one on the exhaust manifold
and theres one on the exhaust pipe after catalyst. So refer to the one on the bottom.

Now - before you go spend your money like a crazy parts changer let me tell you how you test the oxygen sensor for failure.

Before we even start - when you cleared the Code and restarted the car - did it pop the code right away or you had to drive it for a while to pop it back on?

we'll start from here...


P.S. there are alot of problems with electrical systems - those are the hardest to find and there are certain procedures to diagnose it.

 

yes, within a few seconds of starting. i "tested" the sensor before replacing it. unplugged it with engine running. no difference. what i really need to know is if the 2 heater wires that go to the sensor are supposed to carry 12v.

 

I'm not sure what wires are you testing - but connector to the oxygen sensor has 4 wires in it it's a 4 pin connector disconnect it and look inside of that

it suppose to look this way: (when you looking inside of the connector)




[IMG]local://upfiles/439/950B84BA92BF41A5BC5C21F9039EE403.jpg[/IMG]

 

I'm not sure which wires you're testing , but heres how you start the test

Measure the resistance between Pin 3 and Pin 4 (oxygen sensor connector) -----------------> it suppose to be 10-40 Ohm

now refer to the car connector terminal plug check for continuity between pin 3 and the body ground and pin 4 and the body ground--> if theres a continuity Replace O2 sensor (I hope you replaced the right sensor not the manifold one , the one on the bottom.)

if theres no continuity between those terminals proceed on turning the switch ON and measure the voltage between terminal 3 (Yellow/black) and terminal 4(orange/black) on the car plug.

If you getting the voltage - you have to turn to the ECM and unplug the Biggest harness (A connector) turn the ignition Switch ON and now measure the voltage on the terminals 3 and 4. - If you still have the voltage you have a short in Orange/Black wire between the ECU and O2 sensor.
IF you getting NO Voltage Connect A harness to the ECU and O2 sensors and check for voltage between the connectors (A11 yellow/black +) and (A23 Orange/black -) on the A harness (while connected to the computer) with ignition switch ON you should be getting current less than 0.1A monitor it for a couple of minutes (unless the current drops below 0.1A immediately. If it does and it less than 0.1A ---> replace the O2 sensor || If the current more than 0.1A ----> need to replace ECU.


getting back If theres no voltage measure the voltage between terminal 3 (yellow/blacl) and the body --> if theres no Voltage you have an open in Yellow/Black between o2 sensor and PGM-FI main relay.

// connect the O2 sensor and proceed with the part as in first section IF you getting NO Voltage Connect A harness to the ECU and O2 sensors and check for voltage between the connectors (A11 yellow/black +) and (A23 Orange/black -) on the A harness (while connected to the computer) with ignition switch ON you should be getting current less than 0.1A monitor it for a couple of minutes (unless the current drops below 0.1A immediately. If it does and it less than 0.1A ---> replace the O2 sensor || If the current more than 0.1A ----> need to replace ECU.