aftermarket o2 sensor problems

So here is some history on my problem:

2 years ago some idiots stole my catalytic converter, they didn't take any time, just cut it off at the exhaust pipe on either side of the cat and ripped the wiring out of the o2 sensor. I couldn't afford to buy the stock cat, new exhaust, etc. at the time so I went to a shop and had them weld in a generic cat just to get the truck running properly again. It's a 2004 PreRunner SR5 3.4.

However since the cat was now aftermarket I was going to have to install a universal o2 sensor, as the aftermarket cat wouldn't take the oem o2 sensor. The garage didn't have the universal o2 on hand so they just plugged the o2 port and I was on my way.

So for about a year and a half, I left the truck this way. Since there was no o2 sensor hooked up my check engine light was always on. No biggie, I just checked the codes every couple weeks to make sure that the only error I was receiving was the missing sensor.

Well this is all fine and well until I need to smog the truck, so I decide to go ahead and install the universal o2 sensor. The sensor was straight forward and the install was simple. However I still have a check engine light and the same code. I troubleshot the following and still no luck:

The o2 sensor is a 4-wire model; error code is p0038 and only that code

I checked the resistance on the heater, a little low at 4 ohm but seemed good
I checked the heater was receiving 12v with the key in the on position, good
I checked the EFI relay, good
I checked for voltage at the ECM, low at 4v but still there

So everything seems to be working as it should... Is it just that I have a cheap universel o2 sensor and that it isn't jiving with the ecm and cpu to kill that error code?

I'd like to keep from buying a whole new exhaust system as money is still tight so any suggestions for a workaround to make this o2 sensor problem work with my current exhaust setup would be greatly appreciated.

Thank you all for your time and help.

Michael

 

I had a similar issue. It turns out that some Tacoma's do not use a front oxygen sensor. They use an air fuel sensor. When I had to change mine it looked exactly like an oxygen sensor but had an ever so slightly different plug. It ran with the oxygen sensor installed but not quite right. cel kept coming back as well. Your dealer can tell off of your vin which it takes.

 

I had to do this to my taco I went to the auto parts store like three times cuz they screwed up on the sensor.