When a “check engine” light perks up your car or truck’s dashboard, it’s natural to panic. But if an air fuel ratio sensor is stirring up the trouble, there’s no need to worry. Also known as an oxygen sensor, this part is easily identified and replaced when necessary.
So how do you check and replace an oxygen sensor (air fuel ratio sensor)?
Luckily, YouTube mega mechanic ChrisFix lays out these simple steps:
- Identify the problem using an OBD scanner
- Test the two black wires with an ohm meter
- If necessary, remove the old air fuel ratio sensor
- Use an oxygen sensor socket kit to install a new sensor
Using a 2003 Toyota Rav4 as his guinea pig, ChrisFix provides a personal YouTube walk-through on how to test that oxygen sensor. Then you’ll know if you really need to switch it out and how to do just that.
Step 1: Identify the Air Ratio Sensor Problem
Since oxygen sensors (air fuel ratio sensors) are a common issue in lots of vehicles, they usually show up in the coding for “check engine” lights. You’ll often find the problem in Toyota and Lexus automobiles, but it can pop up in just about any car or truck.
Using an OBD scanner, look for a “check engine” light with a diagnostic trouble code (DTC) such as P1155. This is a Bank 2, Sensor One code, which can indicate an air fuel sensor error. In Toyota and Lexus engines, it’s typically the heater element that is shot.
Different vehicle makes and models have various codes to indicate air ratio sensor problems. Before you rush out and buy an expensive new sensor, take a deep breath and explore the possibilities. Simple testing can let you know what you’re looking at.
Step 2: Test the Two Black Wires with an Ohm Meter
In many models, you’ll need to remove the exhaust manifold to reach the sensor. Test the oxygen sensor by following the line to Bank Two, Sensor One, and press on a tab to reveal two black wires.
Test them with your ohm meter, setting it to 200 ohms.
If you see no continuity, the heater circuit is very likely broken. Now that you’ve verified the sensors are bad, it’s time to replace them.
Step 3: Remove the Old Oxygen Sensor
You’ll need to rent or purchase an oxygen sensor socket to get the job done smoothly. There’s a dedicated slot into which you slide the sensor wire, taking care not to strip the old sensor as you move forward.
As you slide the wire in, use a ratchet to remove the old oxygen sensor. You’ll be able to take it off by hand, but it gets pretty hot. So, either let it cool off or wear a pair of welder’s gloves to keep from getting scalded.
Step 4: Install the New Oxygen Sensor
Double-check that your new sensor is similar to the one you’re removing, particularly the length. An oxygen sensor kit typically comes with anti-seize lubricant, so don’t be shy about using it. Pat a small amount right on the threads but avoid letting it slip onto the actual sensor.
Thread the sensor into the hole and tighten it up, taking care not to cross-thread it. Once you wriggle it through, tighten it up with the oxygen sensor socket and connect the clip. There you have your new air fuel ratio sensor.
Test it out again by deleting the codes from the “check engine” light to make sure they don’t trigger again. Start the engine, go for a cruise, and enjoy the satisfaction of a job well done.
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