Circuit Description
The Engine Oil Level Switch is a simple float switch that is grounded when the engine oil level is OK. The PCM checks the Engine Oil Level switch circuit at startup. 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 startup, one of the following conditions must be present:
| • | If the engine coolant temperature was between 15°C (59°F) and 130°C (266°F) at the last key OFF, the engine coolant temperature at key ON must be at least 12°C (22°F) cooler than the engine coolant temperature at the last key OFF. |
| • | If the engine coolant temperature was higher than 82°C (150°F) at the last key OFF, the time between last key OFF and the present key ON must be sufficient to allow the oil to drain back to the sump. The PCM will remain powered up for 10 seconds to ensure that the oil has drained back to the sump. If the key is turned back ON while the PCM is still powered up, the oil level will not be tested. |
The Low Oil Level Lamp will be illuminated for approximately 1 minute 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). When the ignition is first turned ON, the PCM commands the Low Oil Level lamp ON for a brief period of time to test the bulb.
Diagnostic Aids
For diagnosis of the instrument panel, perform the Diagnostic System Check - Instrument Cluster .
Check for the following conditions:
| • | Poor connection at PCM or 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 PCM output circuit. A change in voltage will indicate the location of the fault. |
Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
-
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.
-
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.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 |
Important: Ensure that engine oil level is not low (as indicated on the engine oil level indicator) before continuing diagnosis. Was the On-Board Diagnostic (OBD) System Check performed? | -- | ||||||
2 | Observe Engine Oil Level displayed on the scan tool. Does Engine Oil Level display OK? | -- | Go to Diagnostic Aids | |||||
3 |
Is the test lamp ON? | -- | ||||||
4 |
Caution: Provide additional support when a vehicle is on a hoist:
Is the voltage near the specified value? | B+ | ||||||
5 | Connect the digital multimeter between the engine oil level switch signal circuit and chassis ground. Is the voltage near the specified value? | B+ | ||||||
6 |
Was a problem found? | -- | Go to Diagnostic Aids | |||||
7 |
Was a problem found? | -- | ||||||
8 |
Was a problem found? | -- | ||||||
9 | Locate and repair open in the engine oil level switch ground circuit (CKT 451). Refer to Wiring Repairs in Wiring Systems. Is action complete? | -- | -- | |||||
10 | Replace the engine oil level switch. Refer to Engine Oil Level Indicator Switch Replacement . Is action complete? | -- | -- | |||||
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | -- | ||||||
Does Engine Oil Level display OK? | -- | System OK |
