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Short Summary
Main recommendation: Before buying a new air fuel ratio sensor, test the Bank 2 Sensor 1 heater circuit with an ohmmeter and replace the sensor only if the heater shows no continuity, as demonstrated on a 2003 Toyota RAV4 with a 2-liter four-cylinder engine showing code P1155. The video says this is a common failure on Toyota and Lexus engines, typically because the sensor's heater element goes bad, and the same process applies to any Toyota or Lexus with this engine.
Key Points
- The P1155 code indicates a Bank 2 Sensor 1 air fuel ratio sensor error, and the heater element failure is the typical cause on these engines.
- A continuity test on the two black heater wires confirms whether the sensor is actually faulty before spending money on a replacement, since sensors can be expensive.
- A known-good new sensor is used for comparison: its two black heater wires show resistance, while the faulty sensor showed none.
- The replacement uses a dedicated oxygen sensor socket with a slot for the sensor wire, which prevents stripping the old sensor during removal and eases installation.
- After replacement, clearing the code and taking a test drive confirmed the check engine light did not return.
Details Worth Noting
- Concrete instructions:
- Make sure the engine is cool before working, since the exhaust manifold gets very hot and can cause burns.
- Locate Bank 2 Sensor 1, then follow its wiring up to the connector, press the release tab, and pull the connector apart.
- Set the multimeter to 200 ohms and touch one lead to each of the two black wires in the pigtail. No continuity means the heater circuit is broken. Compare with a new sensor, where the two black wires should show resistance.
- Use an oxygen sensor socket with the slotted design so the sensor wire slides through. If the socket is 3/8 drive and the ratchet is 1/2 inch, a cheater bar (a length of tubing slid over the ratchet handle) gives the leverage needed.
- Once the sensor cracks loose, unscrew it fully by hand, using a welder's glove if still warm.
- Verify the new sensor matches the old one in length and appearance.
- Apply a small amount of anti-seize only to the threads, not the sensor body, which makes future removal easier. Very little is needed.
- Thread the sensor in by hand carefully to avoid cross-threading, then snug it with the socket. It does not need to be extremely tight.
- Snap the electrical clip back into place, clear the stored code, then start the engine and drive to confirm the light stays off.
- The speaker mentions links in the video description for a good oxygen sensor socket kit and for a cheaper source for the sensor.
- The speaker used a rented oxygen sensor socket from a parts store.
Bottom Line
A failed heater circuit is a quick, inexpensive test to run before replacing this sensor, and the replacement itself is manageable with the right socket and careful handling of a hot exhaust component.
