Code P0135 O2 Sensor Heater Circuit Bank 1 Sensor 1

2000 LEXUS GS 300
150,000 MILES • 3.0L • 6 CYL • 2WD • AUTOMATIC
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RYAN.TIM.J
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Hi, have this code from check engine light. Code clears, but then comes back on cold start. Warm start it does not. No impact evident, car drives fine.

Wondering what I am looking at to repair? I assume changing the oxygen sensor is the likely repair?

Thanks,
Tim
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Dec 16, 2019 at 4:52 PM
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JIS001
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Majority of the time it is the A/F sensor heater element that is bad. Ohm out the 2 front upstream sensors. The 2 black wires and let us know the resistance on both sensors. Chances are the right side bank sensor is faulty. Here is a link on how to use a volt meter:

https://www.2carpros.com/articles/how-to-use-a-voltmeter
Dec 17, 2019 at 12:03 AM
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RYAN.TIM.J
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I checked both the front and back sensors. Black to black on the rear sensor is 15 ohm. On the front sensor is 0 or shorted or maybe open.
Jan 11, 2020 at 9:27 AM
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JIS001
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Open circuit.
Jan 11, 2020 at 9:42 AM
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RYAN.TIM.J
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Should both the front and rear sensor be replaced at the same time? To make sure the fuel ratio stays in balance?
Jan 11, 2020 at 11:30 AM
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JIS001
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No, just replacing the one that is bad will be ok. Just make sure you get an A/F sensor and not an oxygen sensor. Big difference in price. The A/F is going to be expensive. If you are buying an aftermarket sensor I personally would recommend a Denso brand.
Jan 11, 2020 at 1:45 PM