Engine Oil Level Sensor/Switch Diagnosis

Circuit Description
The PCM applies 12 volts, through a pull up resistor, to the Engine Oil Level (EOL) switch. The (EOL) Switch is a simple float switch that is grounded when the engine oil level is OK. With the proper engine oil level, the EOL switch voltage input to the PCM is pulled low. If a low oil level condition occurs, the EOL switch circuit is no longer grounded and the EOL switch voltage input to the PCM is pulled high). The PCM sends the EOL switch information via Class II serial data to the Instrument Panel Cluster (IPC). The IPC controls the Low Engine Oil Lamp. The PCM checks the EOL switch circuit at startup. Before checking the state of the EOL switch, the PCM performs a test routine based on time and engine coolant temperature to ensure that the engine oil has drained back into the sump. To test for low oil level at startup, the engine coolant temperature must be greater than 15°C (59°F) and at least 12°C (22°F) cooler than the engine coolant temperature at the last key OFF.

Diagnostic Aids
For diagnosis of the instrument panel, perform the System Check in the Instrument Cluster of Diagrams.

Check for the following conditions:
^ Poor connection at PCM or EOL switch. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the EOL switch and turn the ignition on. Observe a voltmeter connected to the EOL circuit while moving connectors and wiring harnesses related to the EOL circuit. A change in voltage will indicate the location of the fault.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
11. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
12. For the PCM to check engine oil level, startup engine coolant temperature must be at least 12°C (22°F) cooler than the engine coolant temperature was last time the ignition was turned OFF. Allowing the engine to warm and then cool ensures that the PCM checks the engine oil level switch and that the information displayed on the scan tool is current.