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O2 Sensor Heater Codes - New Sensors

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Old 05-06-2018, 11:56 AM
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Default O2 Sensor Heater Codes - New Sensors

Hello, I just recently completed swapping a 2004 GTO motor and T56 into my 91 240sx. I'm using a swap harness from wiring specialties and when I ordered the harness I had no idea what O2 sensors I needed. Apparently, I ordered the harness with F-body style O2 connectors, but I actually should have gotten the GTO style connectors. So I called wiring specialties and they say "Oh yeah, no big deal, just use F-body O2 sensors". Okay. So I ordered some acdelco sensors off rockauto for a 2002 firebird with 5.7L engine and installed them in my long tube headers. Car runs and drives pretty well, but it consistently throws P0135 and P0155, which are O2 sensor heater codes for both front sensors. I'm doing all of my own tuning with EFI Live, and I'm wondering if this issue is a physical difference in the wiring of the O2 sensor or the sensor itself or could it possibly be my tune? Or maybe due to the fact that I'm currently running open header?
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Old 05-07-2018, 06:11 AM
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Default o2 sensors

I'd guess it's a wiring difference, the GTO sensors are not the same as the F-body sensors, you may be able to re-pin the plugs on your harness to match the F-body sensors?
Old 05-07-2018, 08:34 AM
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So where can I find wiring diagrams for the two sensors?

Is it possible that I'll need to just put gto connectors on the harness and use gto sensors?

I should say I'm using the pcm from the 04 gto.
Old 05-07-2018, 10:34 AM
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try this..... http://www.ls1gto.com/forums/showthread.php?t=427908
Old 05-07-2018, 07:28 PM
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Originally Posted by 79LS1FOX
I followed your link and found some decent info. It looks like the wiring harness is correctly wired for the O2 sensors. They even used the same color wires as the OEM harness. I have the 12v ignition source on pin D. The sensor heaters have continuity. I guess I need to see if the PCM is switching the ground for the heaters? Maybe its pinned wrong at the PCM connector?
Old 05-07-2018, 10:23 PM
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I had a similar issue with an '04 Trailblazer harness / green+blue ECU - but only the driver side bank. Eventually gave up trying to figure it out and disabled the check (seemed to run fine, plugs looked okay, O2 feedback voltages looked normal), but when I replaced the ECU with a van unit (in preparation for eventually hooking up the AC), I turned the check back on and the code didn't return. Might be a commonly bad circuit?
Old 05-07-2018, 10:56 PM
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Originally Posted by vertigosity
I had a similar issue with an '04 Trailblazer harness / green+blue ECU - but only the driver side bank. Eventually gave up trying to figure it out and disabled the check (seemed to run fine, plugs looked okay, O2 feedback voltages looked normal), but when I replaced the ECU with a van unit (in preparation for eventually hooking up the AC), I turned the check back on and the code didn't return. Might be a commonly bad circuit?
If I have continuity in the sensor, good power, and good ground, then what are the possible options? Bad sensors?
Old 05-08-2018, 04:33 AM
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On the F-body LS1 the O2 sensor heater diagnostic is actually a time to activity monitor, don't know if the GTO uses the same strategy. But, if it does your open headers may be the issue as the sensors don't heat up as quickly.
Old 05-08-2018, 09:09 PM
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Originally Posted by 71Convertible
On the F-body LS1 the O2 sensor heater diagnostic is actually a time to activity monitor, don't know if the GTO uses the same strategy. But, if it does your open headers may be the issue as the sensors don't heat up as quickly.
Today I verified that the PCM is switching ground. So at this point, I know for a fact that the heaters should be working. Either the resistance of the heater is no bueno or you are correct about the open header affecting sensor temperature. I think I'm gonna just move forward and get the exhaust done and go from there.

I was thinking about it earlier, this must be why people just turn off the MIL within the ECM instead of disabling the DTC processing. Of course, I want the heaters to work, but I don't want to look at the light on the dash. Coming from a background of Nissan tuning and not being able to do that, it's actually a good idea.




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