For 1990-2009 cars

The PCM controlled lamps are intended to alert the driver to an operating condition which may require immediate attention.

The PCM commands the Low Oil Level Lamp ON if the engine oil level sensor indicates that a low oil level condition exists. The PCM determines whether or not to test for low oil level based on the difference between engine coolant temperature at the last shutdown and engine coolant temperature at startup. This is to ensure that the oil has drained back into the oil pan before testing.

### Engine Oil Level Sensor

Engine oil level is determined by an optical sensor which detects oil level immediately upon powerup. While the engine oil level sensor is determining oil level, the sensor holds the state of the engine oil level PCM input circuit at ignition voltage. The amount of time the engine oil level sensor requires to determine oil level is about 1.5 seconds. After the engine oil level has been determined, the engine oil level sensor will ground the engine oil level PCM input circuit for 1 to 2 seconds if oil level is OK or 6 to 10 seconds if oil level is low. The PCM determines oil level based on the engine oil level PCM input signal duration. The PCM also monitors the engine oil level PCM input signal to determine whether the engine oil level PCM input circuit is open or shorted.