If your Chevy Silverado is racking increase miles, girlfriend might notification a far-reaching decrease in fuel economy and engine power. Even though these symptoms are usual of an aging engine, the O2 sensors could be faulty, resulting in your examine engine light to turn on and your truck to failure its emissions test.


This article uses to the Chevrolet Silverado GMT800 (1999-2006).

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O2 sensors measure the oxygen level in her truck"s exhaust gas before and after passing through the catalytic converter. By measuring the amount of oxygen leftover after ~ engine combustion, the truck"s on-board computer can adjust the air-to-fuel ratio accordingly. By keeping this mixture balanced, the computer avoids the engine indigenous running too lean or too rich. If the lot of oxygen is as well low, the engine will start to run rich, meaning it"s dumping un-burnt fuel into the exhaust. If the amount of oxygen is too high, the engine will begin to operation lean, which can lead to detonation and further engine damage if left untreated. Make certain the O2 sensors in your Silverado room functioning properly, and if necessary, replace them by complying with the actions below.

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Materials NeededUpstream O2 sensors (2)Downstream O2 sensors (2)Flat head screwdriver7/8" Crescent wrenchBreaker bar (optional)Wire cutters

There are 4 O2 sensors in 1999 come 2006 Silverado models: 2 upstream and two downstream sensors. The upstream sensors room located in between the exhaust manifold and also the exhaust, if the downstream sensors are situated after the catalytic converter.

Upstream driver"s side O2 sensor: financial institution 1, Sensor 1 (B1/S1)Upstream passenger"s side O2 sensor: financial institution 2, Sensor 1 (B2/S1)Downstream driver"s next O2 sensor: bank 1, Sensor 2 (B1/S2)Downstream passenger"s side O2 sensor: financial institution 2, Sensor 2 (B2/S2)
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Figure 1. Silverado O2 sensor locations.

Replacing the Downstream O2 Sensors

Step 1 – Disconnect the battery and also lift your truck (if needed)

Always disconnect the an unfavorable terminal (black cover) of the battery when working with electric components and also wiring. It"s not crucial to lift her truck, yet you deserve to do therefore for much more work space.

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Step 2 – eliminate the old O2 sensors

Figures 4 v 6 listed below show the replacement of the B2/S2 (passenger"s side) O2 sensor. However, replacement of the B1/S2 (driver"s side) O2 sensor is the same process.

Using your level head screwdriver, pry out the clip hold the wire harness to the sheet metal.Disconnect the O2 sensor cable harness native the sensor.Use the 7/8" Crescent wrench to remove the O2 sensor. You may need a breaker bar because that extra leverage.
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Figure 2. Place of B1/S2 O2 sensor.
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Figure 3. Ar of B2/S2 O2 sensor.
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Figure 4. Un-clip and also remove the cable harness connector.
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Figure 5. Disconnected cable harness connector.
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Figure 6. Unscrew and also remove the O2 sensor.Step 3 – install the brand-new O2 sensorsHand-tighten the new O2 sensor right into place.Use the 7/8" Crescent wrench come tighten the O2 sensor to a snug fit.Reconnect the cable harness to the brand-new O2 sensor.Push the cable harness clip back into place.
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Figure 7. Tighten the new O2 sensor.

Featured Video: exactly how to change Downstream O2 Sensors


Replacing the Upstream O2 Sensors

Step 1 – remove the old O2 sensors

Figures 10 v 12 listed below show the remove of the B2/S1 (passenger"s side) O2 sensor. However, replacement of the B1/S1 (driver"s side) O2 sensor is the exact same process.

Use wire cutters to reduced the clip securing the O2 wire harness come the structure rail.Pull the wire harness free and disconnect it.Using a flat head screwdriver, pry out the metal clip securing the cable harness that"s directly connected to the O2 sensor.Use the 7/8" Crescent wrench to remove the O2 sensor. You may need a breaker bar because that extra leverage.
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Figure 8. B1/S1 O2 sensor location.
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Figure 9. B2/S1 O2 sensor location.
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Figure 10. Clip the pin on the cable harness connector near the framework rail.
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Figure 11. Disconnected cable harness connector.

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Figure 12. Usage a breaker bar to eliminate the sensor if needed.Step 2 – download the new O2 sensorsHand-tighten the brand-new O2 sensor into place.Use the 7/8" Crescent wrench to tighten the O2 sensor come a snug fit.Reconnect the cable harness to the new O2 sensor.Route the cable harness to the framework rail.Push the wire harness clip earlier into place.Start the engine and also let it operation for at least 5 minutes, so the computer can readjust to the new O2 sensor.

Featured Video: exactly how to Install/Replace Upstream O2 Sensor