The crankshaft position sensor--sometimes referred to as the CKP sensor--on a 1998 GMC Sonoma is responsible for sending a signal to the vehicle's ignition system, which the computer uses to reference the RPM and crankshaft position of the engine. If the sensor goes out, the engine computer won't be able to function properly and the "Check engine" light will come on. To fix the problem, you may have to replace the sensor. But to do that, you first have to locate it on the engine.
Open the hood. Crawl underneath the front bumper of the Sonoma and look up toward the bottom of the engine. Turn on the flashlight.
Locate the crankshaft pulley, which is the large pulley at the very bottom of the front of the engine. Shine the flashlight on the pulley.
Look just to the rear of the crankshaft pulley, toward the passenger side of the vehicle. Look for the fitting with the wiring running out of it that is bolted at a 45-degree angle to the bottom of the engine--that is the crank position sensor. It is located at approximately the 8 o'clock position, when compared to the crankshaft pulley.
