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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  • 57 POSTS
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 8:52 AM
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JIS001
  • ✓Experienced Mechanic
  • 3,412 POSTS
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 16, 2019 at 4:03 PM
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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 1:27 AM
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JIS001
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Open circuit.
Jan 11, 2020 at 1:42 AM
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RYAN.TIM.J
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  • 57 POSTS
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 3:30 AM
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JIS001
  • ✓Experienced Mechanic
  • 3,412 POSTS
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 5:45 AM
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