Circuit Description
The engine oil pressure switch is normally closed. When oil pressure increases above 1 to 4.5 psi the switch contacts open. The PCM supplies 12 volts to the oil pressure input circuit. With low oil pressure the 12 volts is pulled low to ground. This diagnostic test checks for an open condition of the low oil pressure switch circuit. If the engine has been off long enough for engine temperature to drop by 10°C, then a shorted (low oil pressure) condition of the circuit should be observed prior to engine running. If the engine has NOT been cranked and oil pressure has been detected, DTC P1189 will set.
Conditions for Running the DTC
| • | DTC's P0116, P0117, P0118 and P1114 not set. |
| • | Ignition on. |
| • | Engine off. |
| • | Engine temperature 10°C less than last key off temperature. |
Conditions for Setting the DTC
Circuit open for 5 seconds
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will not illuminate. |
| • | No message will be displayed. |
Conditions for Clearing the MIL/DTC
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test. |
| • | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. |
| • | Use a scan tool to clear DTCs. |
| • | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation. |
Diagnostic Aids
Check the oil pressure input and switch ground circuits for an intermittent open or for poor oil pressure switch terminal contact. With the engine NOT RUNNING the oil pressure display of the scan tool should indicate LOW. An open switch/circuit would indicate OK with the engine NOT RUNNING.
This DTC only tests the oil pressure circuit for an open condition. If this DTC is not set and further diagnosis of the oil pressure input circuit is required, refer to Oil Pressure Diagnosis and Testing .
Test Description
An example test description follows:
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Checking to see if the fault is present. Low should be displayed with the engine not running.
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Checking to see if the oil pressure switch or wiring is at fault.
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Checking to see if the oil pressure switch input circuit or the PCM is at fault.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Does the scan tool indicate low oil pressure? | -- | |||
Does the scan tool indicate oil pressure low? | -- | |||
Is the resistance the same or less than the value specified? | 5 ohms | |||
5 | Repair the open in either the oil pressure switch input circuit or the oil pressure switch ground circuit. Is the repair complete? | -- | -- | |
6 | Ensure switch terminal contact is OK. If terminal contact is good replace the oil pressure switch. Is the repair complete? | -- | -- | |
7 | Ensure PCM terminal contact is OK. If terminal contact is good replace the PCM. Is the repair complete? | -- | -- |
