The crankshaft position sensor on a Saturn S-Series is a Hall Effect sensor used by the computer to determine the position of the Number 1 cylinder. With this information, the computer can adjust the ignition timing. The sensor is located just above the starter and has a two-wire terminal connector; it has a yellow positive wire and a purple negative wire.
Locate the starter and look directly above it -- you can see the CPS in the block. Pull the electrical connector off the sensor. Place the multimeter on the ohms scale.
Probe the two terminals on the sensor with the leads on the multimeter. Polarity here makes no difference, so either lead can go on either terminal. Read the display on the multimeter. The correct resistance value ranges from 900 to 1200 ohms. If the resistance is much greater or much smaller, replace the CPS.
Plug the electrical connector back on the sensor. Place the multimeter on the 24-volt scale. Place the multimeter's red probe in the sensor's yellow terminal and the black probe in the opposite purple terminal.
Crank the engine over to start the vehicle, with the help of a friend, while watching the display on the multimeter. If the sensor is good, there should be big fluctuations in the voltage; the multimeter should display the battery voltage and then show "0," repeating very rapidly. If the sensor fails any of these tests, it should be replaced.
