If her Chevy Silverado is racking increase miles, girlfriend might notice a far-reaching decrease in fuel economy and also engine power. Also though this symptoms are usual of an aging engine, the O2 sensors might be faulty, leading to your inspect engine light to rotate on and also your truck to failure its emissions test.


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

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O2 sensors measure the oxygen levels in your truck"s exhaust gas before and after passing with the catalytic converter. By measuring the quantity of oxygen leftover after engine combustion, the truck"s on-board computer system can adjust the air-to-fuel proportion accordingly. By maintaining this mixture balanced, the computer prevents the engine from running also lean or too rich. If the amount of oxygen is too low, the engine will start to run rich, meaning it"s dumping un-burnt fuel into the exhaust. If the quantity of oxygen is too high, the engine will begin to run lean, which deserve to lead come detonation and also further engine damage if left untreated. Make certain the O2 sensors in your Silverado space functioning properly, and if necessary, change them by following the procedures 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 four O2 sensors in 1999 come 2006 Silverado models: two upstream and also two downstream sensors. The upstream sensors are located in between the exhaust manifold and the exhaust, if the downstream sensors are located after the catalytic converter.

Upstream driver"s side O2 sensor: financial institution 1, Sensor 1 (B1/S1)Upstream passenger"s side O2 sensor: bank 2, Sensor 1 (B2/S1)Downstream driver"s next O2 sensor: bank 1, Sensor 2 (B1/S2)Downstream passenger"s next O2 sensor: bank 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 lift her truck (if needed)

Always disconnect the an unfavorable terminal (black cover) that the battery when working with electrical components and also wiring. It"s not essential to lift her truck, yet you have the right to do for this reason for more work space.

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Step 2 – eliminate the old O2 sensors

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

Using your flat head screwdriver, pry out the clip stop the wire harness to the paper metal.Disconnect the O2 sensor wire harness indigenous the sensor.Use the 7/8" Crescent wrench to remove the O2 sensor. You may need a breaker bar for extra leverage.
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Figure 2. Place of B1/S2 O2 sensor.
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Figure 3. Place 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 wire harness connector.
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Figure 6. Unscrew and remove the O2 sensor.Step 3 – download the brand-new O2 sensorsHand-tighten the brand-new O2 sensor into place.Use the 7/8" Crescent wrench come tighten the O2 sensor come a snug fit.Reconnect the cable harness come the brand-new O2 sensor.Push the wire harness clip earlier into place.
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Figure 7. Tighten the brand-new O2 sensor.

Featured Video: just how to replace Downstream O2 Sensors


Replacing the Upstream O2 Sensors

Step 1 – eliminate the old O2 sensors

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

Use wire cutters to cut the clip securing the O2 cable harness come the structure rail.Pull the cable harness free and disconnect it.Using a flat head screwdriver, pry the end the steel clip securing the cable harness that"s directly associated to the O2 sensor.Use the 7/8" Crescent wrench to remove the O2 sensor. You might need a breaker bar for 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 wire harness connector close to the frame 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 right into place.Use the 7/8" Crescent wrench come tighten the O2 sensor come a snug fit.Reconnect the cable harness to the brand-new O2 sensor.Route the wire harness to the structure rail.Push the wire harness clip earlier into place.Start the engine and let it run for at least five minutes, therefore the computer system can readjust to the new O2 sensor.

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