Question: I have a 2003 Toyota Sequoia with the 4.7-liter engine and about 85,000 miles. It runs fine, but the Check Engine light came on, and I had the codes read by a friend with a scanner. It was P0052: oxygen sensor. Can I do this myself, or should I bring it to Toyota?

Answer: DTC P0052 refers to a failure of the oxygen sensor heater control circuit -- Bank 2, Sensor 1. The O2 sensor is most accurate in determining oxygen content in the exhaust gases at a certain temperature range. The heater is used to maintain this optimum temperature in all driving conditions. The majority of times P0052 is set in the Electronic Control Module's memory; it's a bad sensor causing the problem -- but not always. It can also be an open or short in the O2 sensor circuits, or the Electronic Control Module itself. The proper testing should be performed to be absolutely sure of the fault before replacing the sensor. But the odds are good you can get away with simply replacing the suspect part. There's a special O2 sensor socket that should be used, and you have to be certain of the sensor location. On the 4.7-liter V-8, there are four oxygen sensors. Two are located before the catalytic converters, and two after (or in). Sometimes the "before" sensors are referred to as air fuel sensors.

Here's where you want to be careful. The part you're dealing with is sensor 1 at bank 2. Sensor 1 tells us it's located before the catalytic converter, between the engine and the cat. Bank 2 means it's on the right (passenger) side of the engine. The labeling of locations can vary from engine to engine, so confirming the location is top priority, or you may be replacing the wrong part. When all is said and done, clear the diagnostic trouble code and road test the vehicle to confirm the repair.



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