Review on 🔌 Denso 234-9021 Upstream Heated Oxygen Sensor: Advanced 4-Wire Plug with 14.17” Harness by Gustavo Mathew

Installed both Denso Air/Fuel Sensors #234-9021 on our 2000 ES 300; Rows 1 and 2. Very easy to remove with a 7/8" open end wrench (22mm is also fine) after applying the penetrant and allowing the engine to warm up for about two minutes. Bank 1 between the engine and firewall wasn't that easy but broke free with a slight nudge. These sensors were replaced after 166,000 miles as part of routine maintenance to avoid the "ignition engine" problems some have experienced. Sensor under Auto 02 will be replaced soon if necessary. One of the earlier complaints related to the use of a fuel additive that could cause a sensor failure. Regularly used "Lukas" fuel and oil additives - no problems. This engine forms sludge and carbon easily, and a fuel additive and regular additive oil changes (3-4k miles) really help. High mileage Valvoline Synthetics are a great product. Would have given the sensors five stars if the packaging was a box rather than an envelope. During the first envelope shipment via UPS, a sensor was crushed and had to be sent back. If envelopes are used, they must be marked as FRAGILE as the sensors must not be dropped or crushed. The new sensors respond well because they are designed for this engine. Arrived safe and sound (in an envelope) to replace. I've driven the car several times, the sensors respond well; No problem. I seem to feel a little more power in the hills than before. It remains to be seen whether consumption will improve.