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 140°C (284°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 140°C (284°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 15 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 about a 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 System Check in the Instrument Cluster section of Electrical Diagnosis.
Check for the following conditions:
| • | Poor connection at PCM or oil level sensor. 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. |
| • | Engine Oil Level Switch circuit: If the problem with the Low Oil Level lamp can not be isolated using the Engine Oil Level Switch Diagnostic table, use the PCM Controlled Lamps Diagnostic table. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart.
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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. Refer to Powertrain Control Module Replacement/Programming .
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Ensure that engine oil level is not low (as indicated on dipstick) before continuing diagnosis. Was the On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 | Observe Oil Level display on the scan tool. Does Oil Level display OK? | -- | Go to Powertrain Control Module Controlled Warning Lamps Diagnosis | |
3 |
Is the testlight ON? | -- | ||
4 |
Does the DVM display voltage near the specified value? | B+ | ||
5 | Connect the DVM between the Oil Level Switch signal circuit and chassis ground. Does the DVM display a voltage near the specified value? | B+ | ||
6 |
Was a problem found? | -- | Refer to Diagnostic Aids | |
7 |
Was a problem found? | -- | ||
8 |
Was a problem found? | -- | ||
9 | Locate and repair open in the Oil Level Switch ground circuit (CKT 451). Refer to Repair Procedures in Electrical Diagnosis. Is action complete?. | -- | -- | |
10 | Replace the Oil Level Switch. Refer to Engine Oil Level Sensor . Is action complete? | -- | -- | |
Replace the PCM. Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | -- | ||
12 | Observe Oil Level display on the scan tool. Does Oil Level display OK? | -- | System OK |
