Engine Oil Level Sensor/Switch Diagnosis

Circuit Description

The engine oil level switch is a float switch that is grounded when the engine oil level is OK. The PCM checks engine oil level at start-up. Before checking the state of the engine oil level 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 start-up, the following conditions must be present:

^ Engine coolant temperature is greater than 15°C (59°F).

^ Engine coolant temperature at key ON must be at least 12°C (22°F) cooler than engine coolant temperature at the last key OFF.

A check engine oil message will be displayed on the IPC information center when the PCM checks for low oil level and the engine oil level switch indicates that a low oil level condition exists (engine oil level switch circuit not grounded).


Diagnostic Aids

For diagnosis of the instrument panel, refer to the Instrument Panel System Check in Electrical Diagnosis. Check for the following conditions:

^ Poor connection at the PCM or the engine oil level 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 PCM and turn the ignition ON. Observe a voltmeter connected to the affected PCM output circuit while moving connectors and wiring harnesses related to the engine oil level switch. A change in voltage will indicate the location of the fault.

^ Instrument panel cluster.

If a problem with a check engine oil message can not be isolated using the Engine Oil Level Switch diagnostic table, refer to the Instrument Cluster System Check in Electrical Diagnosis.


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, start-up 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.