Replaces OEM Part Number:234-4669 234-4651 Fit for:2003 2004 2005 2006 Cadillac Escalade 6.0L 2003 2004 2005 2006 Cadillac Escalade EXT 6.0L 2003 2004 2005 2006 2007 Chevrolet Silverado 1500 6.0L 2006 Chevrolet Suburban 1500 6.0L 2003 2004 2005 2006 GMC Yukon 6.0L 2003 2004 2005 2006 Hummer H2 6.0L 2007 GMC Sierra 1500 Claic 6.0Package included: 2*Upstream & 2*Downstream Note: 1. Please check OEM number before purchasing. 2. Please allow 1-2cm error due to manual measurement. Thanks for your understanding. 3. Monitors are not calibrated same, item color displayed in photos may be showing slightly different from the real object. Please take the real one as standard.Must Know Before Buying:A: The only way to know if the O2 sensor is functioning normally is to check its responsivene to changes in the air/fuel mixture, by Voltage Measurement or Waveform Simulation. Use a 10-megaohm digital voltmeter. Hook up the voltmeter's red probe to the sensor's signal wire and the black probe to engine ground. (Use back probe method, DO NOT pierce the wire.) For a good sensor, voltage should fluctuate constantly between 0.1 and 0.9 volts after starting the engine for 2 or 3 minutes. Please take a video clip of the voltmeter and contact us if our sensor: Goes above range between 0.1 and 0.9 volt Remains below 0.5 volts Stays fixed at a particular voltage You're free to choose replacement or