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2001 Toyota Camry P1135 O2 Sensor Fault: Diagnosis and Correct Part Replacement Guide

Model: 2001 Toyota Camry Fault Code: P1135 Posted: 2009-08-16 18:36

I own a 2001 Toyota Camry with a 4-cylinder engine. Recently, the check engine light activated, and an OBD-II diagnostic revealed code P1135 — indicating a problem with the air/fuel ratio sensor (O2 sensor) in Bank 1, Sensor 1. I initially tested the existing oxygen sensor using an ohmmeter; the reading was 0 ohms, which is abnormal. I replaced it with a new O2 sensor (Denso part #234-9010), which showed a reading of 0.4 ohms. After reinstallation and clearing the code, the check engine light went off initially but returned within one minute. Further testing revealed that when the key was on and the engine off, the female connector terminals showed inconsistent voltage readings: one side read 8 volts, another over 50 volts, while two other slots measured 14V and 16V respectively. This abnormal voltage suggests a potential issue with the sensor harness or connector. My question is: could this be due to a faulty female connector, or does it point to a deeper system-level problem such as wiring faults, sensor misalignment, or incorrect part installation? I’ve since learned that some aftermarket sensors may not match OEM specifications. The original sensor had a Denso part number (in small print), and I later confirmed the correct part for my vehicle is Denso 234-9010 — but it appears to be mispacked in some cases. After replacing with the correct one, the code cleared and the light has remained off since. I’m now seeking clarity on whether this issue stems from a bad connector or if I should consider other factors like wiring integrity or sensor type (e.g., wideband vs conventional). For 4-cylinder engines like mine, is it standard to have only one upstream O2 sensor? Or are there two? Any insights would be greatly appreciated — especially for owners of 2001 Toyota Camry models with 116,000+ miles.

Related fault codes
P1135
Comments (17)
Anonymous 2009-08-17 07:05

Did you purchase your new O2 sensor from a Toyota dealer? On some Toyota models, installing the wrong type — such as a conventional instead of a wideband sensor — can cause persistent P1135 codes. Confirming the correct part is essential.

Anonymous 2009-08-17 16:22

I've tried both conventional and wideband O2 sensors, but the code keeps returning. The car runs significantly better with a wideband sensor, which suggests that was likely the original OEM type installed. My vehicle has 116,000 miles on it.

Anonymous 2009-08-17 17:36

Did you buy the O2 sensor from a Toyota dealership or an auto parts store?

Anonymous 2009-08-17 18:40

No — I bought it at my workplace’s auto parts store. It turned out the sensor in the box was incorrect. After cross-referencing the part number with Toyota's official list, we found that the part listed (234-9010) was actually a mispackaged conventional sensor. We ordered a correct 234-9010 and should receive it by morning.

Anonymous 2009-08-18 06:36

I've seen recurring O2 sensor issues, especially with aftermarket parts. Was Denso the original manufacturer of the OEM part? If not, I’d be cautious about using non-OEM sensors in this application.

Anonymous 2009-08-18 16:23

The old sensor had a Toyota label in small print — it listed Denso as the manufacturer. The new one I received today is the correct OEM-style 234-9010 (first unit was mispacked). After installation, the P1135 code cleared and has not returned. I'm satisfied with the result and thank you for your input, Jeff.

Anonymous 2009-09-14 18:40

I have a 2000 Toyota Camry with the same P1135 issue. The air/fuel sensor (Denso part #234-9010) is located on the front of the engine, behind the exhaust fan. Some posts suggest there’s a 'passenger side' O2 sensor — I want to confirm whether I’m replacing the correct one before spending money. Any advice? Thanks in advance.

Anonymous 2009-09-15 05:24

If your vehicle has a V6 engine with two upstream O2 sensors, it's best to replace both. Even if only one fails, the other may degrade over time and eventually fail too. This helps prevent recurring P1135 codes.

Anonymous 2010-08-08 07:48

Hi, I have a 2001 Camry with 92,500 miles on it and am experiencing the same P1135 code (O2 sensor Bank 1 Sensor 1). After reading previous posts, I’m still unsure which O2 sensor to replace. My vehicle has a 4-cylinder engine — not a V6. Can anyone confirm which one is correct? Thanks — jc

Anonymous 2010-08-08 08:59

For a 4-cylinder engine, the issue likely involves the upstream (pre-cat) O2 sensor. Only use parts sourced from an authorized Toyota dealer to ensure compatibility and proper fitment.

Anonymous 2010-08-08 10:57

Jeff Compton wrote: 'For a 4-cylinder engine, the issue likely involves the upstream (pre-cat) O2 sensor. Only use parts sourced from an authorized Toyota dealer to ensure compatibility and proper fitment.' Thanks — I’ll check pricing at the dealership next. — jc

Anonymous 2010-09-20 12:28

I checked with the dealer. The part for my 2001 Camry (4-cylinder, California emissions) is part #8946733020. The dealership quoted $235.18 — seems high compared to aftermarket Denso sensors I’ve seen online. I’m leaning toward using the Denso 234-9010 part.

Anonymous 2010-09-20 12:30

The Denso part I'm considering is 'DENSO Part # 2349010 {#8946733020} OE-TYPE OXYGEN SENSOR' — priced at $113, half the cost of the dealer part. It's confirmed as an upstream (pre-cat) air/fuel sensor.

Anonymous 2010-09-20 18:26

I called the dealership today and provided my VIN. For a 2001 Camry with L4 engine, California emissions, part #8946733020 — they quoted $263. I’m going to proceed with the aftermarket Denso 234-9010 sensor at $113 instead.

Anonymous 2010-09-21 05:57

Let us know how your experience turns out with the Denso O2 sensor.

Anonymous 2010-09-21 06:57

I’ll update you — I ordered it last night. I need to get a slotted O2 sensor removal socket soon. I’m applying PB Blaster, though I’m not sure how effective it will be given the sensor is in a hot spot.

Anonymous 2010-10-10 18:59

As a follow-up: I installed the Denso part — took only five minutes — and the P1135 code has completely resolved. The check engine light remains off, and the vehicle runs smoothly.