DIY: 4th Gen Toyota Camry Oxygen Sensor

Background noise

Here in the Golden State, we love our clean air! That translates into great things like the smog check that comes once every two years. It so happened that this year, the car that my roommate and I share came due for its biennial check, so it was off to the testing station. Since it had passed when she bought it, we had no reason to believe that it wouldn't do so again. However, other plans were in order and not all was well. The CA smog check consists of three parts: visual of all emissions equipment, a tailpipe "sniffer" test, and a scan of the engine's computer. Imagine my annoyance when it passed the visual and sniffer but still failed due to the ECU throwing a code in the background that wasn't even triggering the check engine light (CEL).

Anyway, time for the fun. I have a code reader, so I plugged it in and discovered what code was actually being thrown in the background (P1135 for those interested). Most auto parts stores (e.g. Autozone, O'Reilly, etc.) will also read it for you for free, though I hear that some complications may exist on that in some states. But if someone is charging $100+ (or really anything) just to read the codes, run. That money can buy your a decent scanner that you can use for years to come.

After getting the code, the best course of action is to immediately turn to Google. That's what I did and in 0.254 seconds, I had over a million hits for the code, including some relevant results on the front page. An intermediate first stop might include obd-codes.com to see what the code is, but in this day and age, an online forum exists for virtually every car produced and with a dedicated knowledge base of individuals who tinker under their hoods. Following the link to some of the top results (from several different forums) kept leading me to the same consensus: pre-cat oxygen sensor.

The best part about forums is that someone has done what you're wanting to do. They've also already bought the parts in question, including the OEMs, the aftermarkets, and the OEM-equivalent aftermarkets. Many manufacturers of "OEM" parts also sell the otherwise identical part unbranded for significantly less than the "OEM" part from the dealer. Between Google and the forums, I was able to determine that this Denso sensor (PN 234-9010) was the unbranded version of the "Toyota" sensor I needed. I wasted no time in ordering it as it was less than half the price the dealer was charging for the "OEM" part.

Oxygen sensor and wire
location in engine bay.

Once the part arrived, the real fun began. This is probably one of the easiest repairs on this car period, especially compared to some other cars I've worked on. If you can see into the engine bay, you can do it! I didn't even need gloves to keep my hands clean, that's how easy it was. Still, here goes. Maybe I'm too detailed, but that's alright.

Removing the sensor

First things first, you need to locate the sensor. Fortunately, this is so easy to do because it's literally right in front of you. It looks like the engine bay was designed for the V6 model, so there's a wealth of open space that makes the 4-cylinder model look extremely empty. Just open the hood and presto!, there it is. It's what the wire sticking out of the exhaust manifold heat shield is for. They sell special sockets for use on oxygen sensors that have cutouts for the wire, but you could make a plain 22mm socket work too or see if a neighbor/friend has one that you can borrow.

After locating the sensor, disconnect its wire from the wiring harness then use the socket to remove it. This may require the application of a penetrating compound (i.e. PB Blaster) and/or the use of a long bar on the wrench handle for torque. Also important is making sure the manifold is cool. This is not just to avoid getting some nice new scars, but also to make sure that you can remove the sensor. If it and the manifold are hot, it'll be much harder to remove. Breaking it off in the manifold would not be beneficial at all.

Installing the new sensor

Don't you just love instructions? "Installation is the reverse of removal" usually greets you on many parts packages for parts that require a degree in process engineering to understand. Fortunately, this instance of that is straight to the point. As it is, there're only two steps to remember: screw in the sensor and connect the wire. It really is that simple! Optional is applying the anti-seize compound to the threads of the new sensors. If you decide to do so, take care to not get any on the sensor itself. They don't take too kindly to be handled at all, much less to getting goop on them. After everything's all wrapped up in the bay, head back under the dash to clear the CEL. The code reader should have a button for doing so. Clear the code, then go drive for a bit. The goal is for the CEL to not come back on. (Of course, if it was on for multiple codes but you've only addressed one problem, it likely will come back on for the other stuff. But P1135 should be gone for good.) If it does throw P1135 again, check to make sure that the wire is plugged in properly before totally freaking out.

Today, the drudgery of owning a Camry just decreased a little. This fix is good for 4-cylinder Camrys from 1991-2001, all of which are well within the price point of a good Mustachian car by now. It's probably applicable to any other vehicle using the Toyota 5S-FE engine, but I'm not a Toyota guy so I couldn't tell you which ones fall into that category. If not, don't despair. Google and forums are your friend. Happy wrenching and I'll be back with other money-saving repair tips in the future!

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