The 2004 GMC Sierra truck has several O2 or oxygen sensors in the system. On the V8 engine equipped trucks, there is one in each exhaust pipe in front of the catalytic converter as well as one on the down pipe coming from the exhaust manifold. When determining if you need to change an O2 sensor, you need to note which one of the sensors is faulty so you can replace the right one. This information will be stored in the truck's computer, so have it scanned before you change the sensors. Most auto parts stores will do this for you free of charge.
Things You'll Need
- Jack stands
- O2 sensor socket
- 3/8-inch drive ratchet
Position a jack under the front suspension of the truck and raise it off the ground. Position a set of jack stands under the front suspension or frame rails to support the truck, then lower the jack and remove it from under the truck.
Locate the O2 sensor you intend to change. If it is the upstream sensor, find it under the engine in the down tube that runs from the exhaust manifold to the catalytic converter. If it is a downstream sensor, it is in the exhaust pipe just in front of the catalytic converter. On dual exhaust trucks, there are two downstream sensors on in each pipe.
Locate the wiring harness pigtail coming out of the top of the O2 sensor. Follow the wires up to the electrical connector at the vehicle wiring harness. Disconnect the connector by pushing down the locking tab on the connector and pulling the two halves of the connector apart.
Place an O2 sensor socket on the O2 sensor in the exhaust pipe. If you do not have one, you can buy an O2 sensor socket at most auto parts stores. Using a 3/8-inch drive ratchet, turn the socket counterclockwise, loosening the sensor. Lift the old sensor out of the pipe and discard it.
Thread the new O2 sensor into the hole in the pipe by hand to avoid stripping or cross threading fit. Tighten it with the O2 sensor socket and ratchet, then run the wiring harness pigtail up to the connector on the truck. Push the connector on the O2 sensor into the wiring harness connector, making sure the locking tab engages. Repeat this process for each O2 sensor that you need to change.
Position your jack under the front of the truck again and lift the truck off the jack stands. Remove the stands from under the truck and carefully lower the truck to the ground.
- "Haynes Repair Manual 1999 to 2006 Chevrolet Silverado GMC Sierra"; Ken Freund; 2008
- Photo Credit Jupiterimages/Photos.com/Getty Images
GMC Savana Problems
The GMC Savana is a full-size van manufactured by the General Motors Truck Company, a division of General Motors (GM) that specializes...
Difference Between Upstream & Downstream Oxygen Sensors
All post-1996 vehicles have a lot of emissions equipment, including oxygen sensors. Most emission-controlled cars have two to four oxygen sensors, depending...
How to Replace the Wheel Speed Sensor in a GMC Sierra
On a car with anti-lock brakes, the wheel speed sensor (WSS) determines the speed of the wheels. To do this, the WSS...
How to Replace an Oxygen Sensor on a 2000 GMC Sonoma
There are two oxygen sensors on a 2000 GMC Sonoma. One is located on the left (driver's side) of the Y-pipe up...
How to Replace a GMC Sierra Crank Sensor
The crank sensor (properly known as the crankshaft position sensor or CKP) on a GMC Sierra is a small magnetic sensor that...
How to Clean a Silverado Oxygen Sensor
The oxygen sensor, or O2 sensor, in your Chevy Silverado collects information about your truck's emissions output and sends this information to...
How to Change an Oxygen Sensor in a GMC Envoy
The GMC Envoy’s oxygen sensor is a critical component for your vehicle. The oxygen sensor monitors the amount of unburned oxygen that...
How to Replace the Oxygen Sensor on a GMC Yukon
If your GMC Yukon is running rough or burning through more gas than usual--and especially if these symptoms are combined with an...
How to Replace the Speed Sensor on a GMC Vehicle
The speed sensor in your GMC vehicle provides a signal to the on-board computer that is used to calculate the speed of...
How to Locate a Knock Sensor on a GMC 1500
The knock sensor on the GMC 1500 is used to sense excess vibrations in the engine caused by the wrong air-to-fuel mixture....