O2 sensor codes

[robert_63]

My 5.3 ls swap is now throwing o2 sensor codes, I didn't see the Code number at autozone where they read it, but the guy said Both sensors showing codes for the 02 heater. What are the chances that both sensors went out at same time? The engine and trans had 140,xxx miles on them and the sensors laid around in my toolbox almost a year before I got the truck running. I have about 300 miles on truck since swap and it just started showing the codes.
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[BR3W CITY]

What is your harness set up for? I've seen a couple guys put universal oldschool o2's on, and many of those don't have the heater circuit.

The Bosch's that many of us use, or the stock o2's should have the built in heater circuit. It would be weird to think it took 300 miles tho.

My o2's come close to the headers, you sure the wires didn't lay on something hot?

Get the DTC it will tell us a tad more.

[BigRed76]

If it took 300 miles to set those codes then it's probably safe to say your wiring harness was modified correctly, like Br3w City said make sure the O2 sensor wires didn't get melted. But I wouldn't be surprised if it just needs two new o2 sensors, they are a maintenance item.