The upstream or primary Chevy Silverado Oxygen Sensor is primarily responsible for reading the exhaust stream. This sensor analyzes what the air fuel ratio of your engine, and relays this information back to your Powertrain Control Module. Your PCM then uses this information to make adjustments on the fly to your fuel injector duty cycle.
The Silverado Oxygen Sensor is also known as the 02 sensor, and today I’ll be showing you how to test it in a 2001 5.3 liter equipped truck. To replace your primary 02 sensor, you will need to identify which bank it’s on. This front 02 sensor is also referred to as the Sensor 1 oxygen sensor or 02 sensor.
Over time your Silverado Oxygen Sensor may become fouled or fail all together. When this happens your PCM is basically operating blind and cannot maintain a stoichiometric and efficient engine operation.
This leads to an overly rich or lean running engine, which can cause problems to your Chevy truck. If your Silverado runs lean for too long, or during hard acceleration it can cause engine pinging or pre-detonation. Left alone this can cause premature damage or catastrophic failure of your engine.
If you need a guide on how to troubleshoot and test your downstream 02 sensor, check this guide here. To complete this How To Guide on testing your Silverado Oxygen Sensor you’ll need a digital multimeter. Have no idea what that is or how to use one? Check this guide here.
Before you begin this guide, you will need to determine whether or not your 5.3 liter engine is a Vortec unit. Usually you can open the hood to see the letters VORTEC stamped on the engine cover. If you aren’t sure check our guide on How To tell if you have a Vortec engine.
How To Test a Primary Silverado Oxygen Sensor
To begin you will need to find the primary 02 sensor that has gone bad on you. If you have a OBDII check engine code for Sensor 1, get a scan tool and determine which bank your problem sensor is located on. Although both of these sensors are basically the same, you will need different testing methods to determine if the primary 02 sensor has gone bad.
Here is the wiring pinout for your Sensor 1 oxygen sensors, make sure to refer to them below.
Out of these four wires you will be checking for power and ground first. These power wires on your Silverado Oxygen Sensor are also known as the heater wires.
Bank 1 Sensor 1 Silverado Oxygen Sensor wiring diagram
Wire 1 and Wire 2 are TAN and PURPLE respectively. These two wires are the ones that transmit the signal to your PCM. Wire 3 and Wire 4 are BLACK and PINK respectively and we’ll be checking Wire 4 for power first.
Bank 2 Sensor 1 Silverado Oxygen Sensor wiring diagram
This side of the wiring harness is slightly different, as the wiring in your engine bay will differ. Wire 1 and Wire 2 are TAN with a WHITE stripe and PURPLE with a WHITE stripe respectively. These two wires are the ones that transmit the signal to your PCM. Wire 3 and Wire 4 are BLACK and PINK respectively and we’ll be checking Wire 4 for power first.
Now that you know what sensor is what we’ll start testing for power on your Silverado Oxygen Sensor. Find your primary 02 sensor and unplug the unit, and then get into your truck and turn the ignition to the “ON” position.
Gently probe the ENGINE harness side of your Silverado Oxygen Sensor connector. You are checking for PIN 4, or the PINK wire for a 12 volt power signal. If you have power at this wire, move on to PIN 3 or the BLACK wire. There should be a ground signal present at this wiring harness.
If you have power and ground at these two wires, this means that your primary Silverado Oxygen Sensor is powered and heated correctly. Now move onto checking the internal resistance of your 02 sensor.
How To Check the Internal Resistance of your Primary Silverado Oxygen Sensor
Now you will be using your multimeter to test the heater element of your oxygen sensor. Where we were testing the ENGINE harness side of your Silverado Oxygen Sensor in the test above, now we will be checking the SENSOR side.
Place the multimeter into OHMS mode, and probe WIRE 1 which should be the H02S Low signal. Now probe WIRE 2 which represents the High signal. If you’ve performed this test correctly and your Silverado Oxygen Sensor is in good condition, there should be between 5-19 Ω.
If these readings are not within these guidelines, your Silverado Oxygen Sensor is bad and must be replaced. Unscrew your primary 02 sensor using a 24mm open wrench or a 02 socket, and install a replacement right away.
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