The oil pressure sending unit on a 2003 GMC Sierra is a screw-in transducer that sends an electrical signal, via the vehicle's main computer, to the instrument panel, which displays a relative indication of the oil pressure for the driver's information. The sending unit's voltage varies depending on how much pressure it registers. The higher the voltage, the higher the oil pressure. Removing the sending unit requires a special socket, which is available at auto parts stores.
Raise the hood on the GMC Sierra. Use the appropriate size socket and ratchet wrench to remove the bolt that secures the plastic engine shield over the intake manifold, located in the top center of the engine. Lift the shield and pull it forward, off the engine.
Locate the oil pressure sending unit behind the rear of the intake manifold. It is a black plastic tube about 3-inches tall.
Remove the electrical connector from the top of the sending unit by pulling the connection off the fitting. Use a ratchet to remove the sending unit with a J-41712 sensor socket or equivalent.
Apply GM recommended 12346004 Teflon pipe & thread sealant or equivalent to the sensor threads.
Use a torque wrench with a J-41712 sensor socket or equivalent to tighten the sensor to 15 foot-pounds.
Push the electrical connection back into the fitting on top of the sensor.
Replace the engine shield and retaining bolt.
