98 Civic O2 Sensor Heater Circuit, Check Engine Light

[nan00k]

Please help! I need to get a smog test right away before my registration expires but something is wrong with my Oxygen Sensor so I'll fail the smog test.

 

I'm hoping to fix it myself if it's not too complicated. All suggestions are most appreciated.

 

Here's the sitch:

 

2 weeks ago a mechanic printed out a diagnostic report which had the following code: PO135 "O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)" He told me I could just swap out the sensor and everything would be fine.

 

So I did. I replaced it with a NAPA part that was listed as the OEM part (however, the sensor I pulled out was a Denso, and the NAPA replacement "OEM" part is a Bosch. ?).

 

Another mechanic, who helped me pull out the original, plugged in his little ECM controller and erased the error code. But the check engine light never turned off. He told me to drive for 20 miles or so and it would reset. That was two weeks ago and it is still on.

 

So it seems like there is a problem somewhere in the circuit upstream of the sensor pigtail. This afternoon I poked my multimeter into the 4 wire connector and got zero volts across the various combinations of terminals, suggesting that there is no power to the sensor. At this point a few specific questions come to mind:

 

1) Where are the fuses for the O2 sensor located?

2) Which wires connect the Heater Circuit? (the wires are in a 2x2 connector)

3) What voltage should the Heater Circuit show?

 

Again, if anybody has any answers to the above and/or suggestions in general I'd be extremely grateful!

 

Thanks a lot,

 

Will

[cranny]

try resetting the ecy yourself. go in your under hood fuse box , pull out the backup fuse for 2 minutes , fire it back in and start it up. all the sensors in the car get thier power from one wire. yellow/black wire. which gets its feed from the main relay.

[nan00k]

try resetting the ecy yourself. go in your under hood fuse box , pull out the backup fuse for 2 minutes , fire it back in and start it up. all the sensors in the car get thier power from one wire. yellow/black wire. which gets its feed from the main relay.

 

Hey, thanks for the suggestion. I tried removing fuse number 11 (labeled "F/I E/M", rated 15A, located in the rear left position as viewed from front of car) for a few minutes and then replacing it. The light is still on. Was that the fuse you were referring to? (I'm not sure what you mean by "backup fuse".)

 

Incidentally, I also tried unplugging the battery as suggested in other posts elsewhere, but that just erased my radio presets.

 

I did see that my O2 sensor cable assembly has a yel/blk wire. Do you know how I could check for continuity in that wire? Is there a pin on the other end of the wire I can access somehow?

 

Thanks again for any help.

[crxtacy]

Napa o2 sensors ,they don't come with a pigtail connector am I right? you gotta use the existing connector and splice it in .If so, try re-checking the wirings. Or maybe napa sold you the wrong one.Sold you an o2 sensor without the heater .?

[nan00k]

Napa o2 sensors ,they don't come with a pigtail connector am I right? you gotta use the existing connector and splice it in .If so, try re-checking the wirings. Or maybe napa sold you the wrong one.Sold you an o2 sensor without the heater .?

 

Thanks for your suggestion. The new sensor did come with a pigtail and it turns out that everything was fine. Apparently my check engine light was still on because the trouble code had not been erased, as I thought it had. All set now. Thanks again.