O2 sensor help

**p moore** · 04-20-2009, 02:32 PM

Hey guys;
New guy here. I have a question for yall. I have a 2004 GMC Sierra 5.3L with 55,000 miles. I have been a few rounds with my Check engine light. So far, it is winning. This past weekend, I spent a few hours replacing the knock sensors, the intake gaskets, and the drivers side pre cat O2 sensor. I drove it around for a while that day and have been to town a couple times. However this morning comming to work, 35 miles, the light comes back on. When I get to work, I check the code. This time I got a P0135. I believe this is theO2 heater circuit. Can I test this for 12V with the key on? If I do not get voltage then, Is there a fuse for this, or where does voltage come from.

Thanks,

Paul

**L0sts0ul** · 04-24-2009, 06:50 PM

just to make sure, you have a 3 wire o2 sensor right? If you do, then yes you can meter for your voltages. Get back to me with your wire count, and colors, and I will tell you which wires you need to meter.... come to think of it... you may hav a 5 wire

**Blazerado** · 04-24-2009, 08:03 PM

If you have the time and energy, and hate electrical stuff as much as i do. Take the corresponding sensor from the other side and flop them, clear the code and start again. If the code changes banks then you know.

**p moore** · 05-04-2009, 09:52 AM

Sorry guys for the late responce.I have been on vacation.

i did swap the sensor to the after cat location and the code followed. I have requested a replacement. It was a 4 wire model BTW.

Thanks for your sugestions and help.

Paul