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How to Replace an Oxygen Sensor in a 1999 Blazer

The Chevy Blazer has the same 4.3 liter engine, the same chassis and the same exhaust components from 1994 to 1999. This includes the two oxygen sensors. The bank one sensor is located on the left side (drivers side) of the front exhaust Y-pipe. The bank two sensor is located just before the catalytic convertor in the exhaust pipe. Which oxygen sensor needs to be replaced will require an OBD II (On Board Diagnostics II) computer code reader or scan tool to determine the culprit. They are removed the same way, but the bank two sensor is much easier to get to. However, the parts and labor estimate may to replace the sensor may help you decide to take on the job yourself with just a few tools.

Instructions

1

Drive the 1999 Blazer up on car ramps to raise the front end. If you do not have car ramps, lift the front of the Blazer on a flat, level paved or concrete surface using a floor jack and two jack stands placed under the front frame rails. Apply the parking brake.

2

Place a wheel chock behind one of the rear wheels.

3

Put on the safety glasses and crawl under the Blazer (on a creeper if you have one) and bring the remaining tools with you.

4

Locate the oxygen sensor to replace. The bank one sensor is up under the left drivers side just forward of the front exhaust Y-pipe. The bank two sensor is located in the exhaust pipe just forward of the catalytic converter.

5

Follow the wire harness plugged into the oxygen sensor youre replacing. Using the small straight edged screwdriver, press in the lock clip of the plug and unplug the oxygen sensor wire from the harness.

6

Place the 22 millimeter wrench or oxygen sensor socket and ratchet onto the oxygen sensor and turn it to the left to release it. If it does not want to release, light the hand held portable propane torch and heat the exhaust pipe around the edge of the oxygen sensor. Do not heat the oxygen sensor, too. Just the pipe around it. Try to loosen the sensor until youre successful. If you had to use the torch, allow the exhaust pipe to cool down and just take a break.

7

Apply a light coat of high-temperature anti-seize lubricant to the threads of the new oxygen sensor only if there is not already some on them.

8

Screw the new oxygen sensor into the port. Tighten with the wrench or socket and ratchet. Do not over-tighten. The sensor only has about 4 to 5 threads and stripping those threads would be futile to the sensor.

9

Plug the sensor wire back into the wire harness.

10

Collect all the tools and debris from under the Blazer. Remove the wheel chock and lower the Blazer.