Denso234-9002 Air Fuel Ratio Sensor

Working on a stubborn check engine light issue. The error code indicated a bad heater circuit on the Air/Fuel ratio sensor (Bank 1, sensor 1) on a 2002 4Runner (3.4L V6). Checked the heater circuit and it was reading approx 20 ohms resistance. Without a reference I was calling it good (was an open circuit) but an online video cited the spec at 1.3-1.6 ohms on a good heater circuit (the two black wires).Bit the bullet after shopping around. A couple sellers have a '10 yr warranty' but they are hard to work with. Installed easily (two bolt installation before the catalyst under the pass side floor.). I did check the heater circuit resistance by poking two small holes in the plastic bag. 1.4 ohms. Viola' !!!!Cleared the code and the short term and long term fuel trims came back into spec. Nice part and it works. Given the cost, be sure to verify its needed. A local shop wants over $150 for 'diagnostics' (a license to steal!) They just check the codes and pronounce "You need a new Air / Fuel ratio sensor!" and want to charge you $350-500 to install one. Buy this quality part and do it yourself in 15 minutes. Then take your better half out for dinner with the savings!

I own a 2003 Toyota Tacoma 2WD EXT cab with an automatic transmission and 2.4 liter 4-cylinder engine. The vehicle has 65,000 miles.I recently got a CHECK ENGINE amber light. I attached my OBDII Diagnostic Reader/Scanner device which I purchased on Amazon a few years ago and discovered a P0135 code. This indicates a fault in the Air Fuel Sensor (aka, O2 Sensor…used interchangeably), Bank 1, Sensor 1, and more specifically, a fault in the forward Air Fuel Sensor Heater Circuit. The Toyota ECU expects to see the Air Fuel Sensor electrically heated to a pre-determined temperature in a specified period of time after start, or it will send a P0135 code.There are two O2 sensors on my Tacoma (four on some of the Toyota V8’s), one located immediately before the catalytic convertor and one immediately behind it. “Bank 1” is the forward of the two O2 sensors. The Sensor internal heater circuit is NOT repairable, so unless you have a short in your wiring leading to the sensor, a replacement O2 Sensor is in order if you’ve received the P0135 OBDII diagnostic code.Denso is the OEM manufacturer for the Toyota Air Fuel sensors. They are built EXACTLY to Toyota specs. The Toyota ECU is looking for VERY SPECIFIC DATA from these sensors. While some of the after market Chinese air fuel sensors offered on Amazon are less expensive, they may not meet specific Toyota ECU specs and will trip a CHECK ENGINE amber light regardless of their age. Accordingly, I recommend the Denso OEM Air Fuel Sensors to avoid any of these issues. When ordering the Denso Air Fuel Sensor on Amazon make absolutely sure you list ALL your vehicle details…model year, specific model type, specific engine size, manual or automatic transmission, etc. as the sensors vary in design based upon each of the preceding. You can check the Denso web site to cross reference what Amazon is showing as the correct part for additional peace of mind.Removing the old part and installing the new one doesn’t require a great deal of mechanical expertise. Your Toyota dealer will quote $350-$400 for parts and labor to complete the job. You can do it for the cost of the Denso OEM part on Amazon and your willingness to climb under your truck.The tools recommended for the job are:1. 12mm socket2. 12mm open end wrench3. 10mm socket4. 10mm open end wrench5. socket wrench6. small flat head screwdriver7. diagonal cutters8. Zip-tie9. Heat resistant anti-seize compoundToyota is notorious for their positive-locking electric connections, and this part is no exception. The electrical connector has a tiny locking tab located on the side of the connector which must be released to separate the male and female ends. More on that later.Here’s what I recommend to complete the process:1. Remove the electrical connector metal support bracket to allow easy access to the electrical connection. Use diagonal cutters to cut any retaining parts for the electrical cable. Use a 10mm socket and/or 10mm open end wrench to do this. It’s tight quarters…very tedious…one click at a time. BUT…it’s the only way you can truly obtain access/purchase to remove the electrical connection. This is the “easy” part…reattaching the bracket later is THE most difficult part of this entire job.2. Remove the old O2 sensor from the exhaust pipe. I used both an open end 12mm wrench and 12mm socket. If the bolts are rusted use your favorite penetrating oil. I applied this a day before I did the job.3. Separate the electrical connection. ****Here’s the trick to removing an infamous Toyota electrical connection: use a small flat head screwdriver to drive under the plastic locking clamp on the SHORTER SIDE of the electrical connector to move it up and off the plastic locking tab.**** If you do this you can easily pull the connector apart using you fingers.4. Install the new Air Fuel sensor. I began with the electrical connector. Push the male sensor connector on to the female connector attached to your vehicle. There are two ribs on the side of the connector to ensure you get this aligned correctly. You’ll hear a “snap” as the parts mate and the locking tab secures the two parts.5. Coat the 12mm studs with anti-seize compound. Place the NEW gasket on the fitting…DO NOT re-use an old gasket. Denso includes a new gasket with each sensor part. Using caution not to get anti-seize compound on the new sensor, slide it over the studs. Hand tighten the 12mm nuts. Then ALTERNATE tightening each nut in SMALL INCREMENTS until you’ve reached the magical 14 foot-pounds of torque recommended in the Toyota shop manual. If you have any doubt regarding the cleanliness of the sensor…clean it with isopropyl alcohol before installation.6. Now the HARD PART: reinstalling the electrical connection supporting bracket. This will be a tedious process. I initially aligned the bolt on the bracket and after MULTIPLE ATTEMPTS…finally got the bolt started. I hand-tightened it from there…and then used the 10mm socket. This process will test your patience…but you’ll eventually get it. Just think of the several hundred bucks you’ve saved to keep your sense of humor.7. Install a zip-tie to secure the O2 sensor electrical lead to one of the metal automatic transmissions lines…or whatever your vehicle originally had in place to secure the lead.8. Reset your OBDII to eliminate the P0135 code.9. Drive your truck long enough to allow it to become fully heated to normal operating temperature. The Toyota ECU expects to see the Air Fuel Sensor electrically heated to a pre-determined temperature in a specified period of time after start, or it will send a P0135 code. If your vehicle is fully warmed up…and you don’t get a CHECK ENGINE amber light…congratulations…you fixed the problem! I always turn off the engine and ignition and re-start a few times just to be sure.10. Politely apologize to your neighbors for any profanity they might’ve overheard during you many attempts to re-attach the electrical connection support bracket.I’ve attached photos of the major aspects of the installation process. Good luck!

Worked great, solved my check engine light issue.

When my check engine light recently came on in my 2002 Toyota 4Runner Sport Edition, it was the first time. I had just gone over the 110k mark. My 4runner has been the most reliable vehicle I have ever owned. I just make sure to do all the scheduled maintenance.I did some research online, and some blogs recommended taking the gas cap off and putting it back on, then unhooking the battery and letting it sit for 10 minutes. I did this and the check engine light went off. It stayed off for about 5 days, but then it came back on. I tried it one more time, and it went off but came back on 10 minutes later. I then decided to take other action.Since my registration was due soon and I had to get a smog check, I decided to buy an auto code reader (on Amazon) for about $15. This was a great purchase, I highly recommend that everyone get one. The code reader pulled P1135, and after more internet research, I found the Denso 234-9002 Air Fuel Ratio Sensor on Amazon. Thanks to all of the other great reviews written about this product, I decided to pull the trigger and do this job myself. I just don't trust auto dealerships at all. I do trust my mechanic but this seemed like an easy enough fix and no special tools were needed. All it took was a combo 12mm/10mm wrench (got it on Amazon) and a small flathead screwdriver to release the wire harness. The 10mm side of the wrench was to take off the bracket that holds the wire harness up. It might be tough to unplug the wire harness without removing the bracket. The 12mm side of the wrench removes the 2 nuts that secure the sensor in place. The sensor even came with a new gasket, so I didn't have to worry about that. The whole job took less than 15 minutes, and I didn't even have to jack up my 4runner. Just slid under it, located the part, and done!After the install, I used the code reader to clear the codes from my 4runner. I then drove about 15 miles, and then tested it again. No codes came up! The next test was the smog check, which I passed easily. I have now driven about 600 miles since installation, and so far so good.I highly recommend buying this part from Amazon, you will save yourself some bucks!

I purchased an 02 sensor from another vendor & ordered it for a 4x4 model by mistake. Sent it back & looked to Amazon for a quick solution since I'd already removed the failed sensor in my '02 Toyota 4Runner SR-5 RWD. Amazon's selection of quality Denso parts got me back on the road within 2 days. No more "Check Engine" light, no more FAULT codes. Immediate results. So far, so good. Easy to install, & saved about $120 on the part too. Highly recommended by this DIY Chick : ) Thanks!