Pinpoint Tests AB: The Low Oil Pressure Warning Indicator Is Never/Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test AB: The Low Oil Pressure Warning Indicator Is Never/Always On (Gasoline Only)
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information. Diagrams By Number
Normal Operation
The engine oil pressure switch is hardwired to the PCM. The Instrument Panel Cluster (IPC) receives the engine oil pressure status from the PCM over the High Speed Controller Area Network (HS-CAN) communication bus. The PCM provides a reference voltage to the engine oil pressure switch when the ignition key is in the RUN position. When there is low or no oil pressure, the engine oil pressure switch remains open. The PCM detects no change in the reference voltage and provides the IPC a request to illuminate the low oil pressure warning indicator. With the engine running and sufficient oil pressure, the engine oil pressure switch closes, pulling the reference voltage low. The PCM detects the low reference voltage and provides the IPC a request to turn off the low oil pressure warning indicator.
If the IPC fails to receive the oil pressure status from the PCM for 5 seconds or less, the IPC defaults the low oil pressure warning indicator to the last state (on or off), based upon the last known good oil pressure status message. If the IPC fails to receive the oil pressure status from the PCM for more than 5 seconds, the IPC sets DTC U0100:00 in continuous memory and defaults the low oil pressure warning indicator on.
- DTC P1678 (Low Oil Pressure Lamp Control Circuit) - sets in the PCM if the oil pressure status indicates oil pressure is present with engine off for 2 seconds.
NOTE: If DTC U0100:00 sets in the IPC, other observable symptoms may be an inoperative speedometer, tachometer, temperature gauge or odometer.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Engine oil pressure switch
- Base engine oil pressure concern
- PCM
- IPC
PINPOINT TEST AB: THE LOW OIL PRESSURE WARNING INDICATOR IS NEVER/ALWAYS ON (GASOLINE ONLY)
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
NOTE: Failure to disconnect the battery when instructed results in false resistance readings. Refer to Battery, Mounting and Cables Battery Disconnect / Connect.
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AB1 CARRY OUT THE IPC INDICATOR LAMP CONTROL ACTIVE COMMAND USING THE SCAN TOOL
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IPC DataLogger.
- Select the IPC low oil pressure warning indicator (OIL_P_LOW) active command. Command the low oil pressure warning indicator on and off. Observe the low oil pressure warning indicator.
- Does the low oil pressure warning indicator illuminate when commanded on and turn off when commanded off?
Yes
If the low oil pressure warning indicator is never on, GO to AB2. If the low oil pressure warning indicator is always on, GO to AB4.
No
INSTALL a new IPC. REFER to Instrument Panel Cluster (IPC) Instrument Panel Cluster (IPC). TEST the system for normal operation.
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AB2 CHECK FOR A STUCK CLOSED ENGINE OIL PRESSURE SWITCH
- Ignition OFF.
- Disconnect: Engine Oil Pressure Switch C103.
- Ignition ON.
- Observe the low oil pressure indicator.
- Does the low oil pressure warning indicator turn on?
Yes
INSTALL a new engine oil pressure switch. REFER to Engine Service and Repair. TEST the system for normal operation.
No
GO to AB3.
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AB3 CHECK THE OIL PRESSURE INPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: PCM C175e.
- Measure the resistance between the PCM C175e-24, circuit CMC24 (GY), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to AB8.
No
REPAIR circuit CMC24 (GY) for a short to ground. TEST the system for normal operation.
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AB4 RETRIEVE THE RECORDED DTCs FROM THE IPC SELF-TEST
- Check for recorded IPC DTCs from the self-test.
- Is DTC U0100:00 recorded?
Yes
GO to Pinpoint Test BA. Pinpoint Tests BA: DTC U0100:00
No
GO to AB5.
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AB5 CHECK FOR A STUCK OPEN ENGINE OIL PRESSURE SWITCH
- Ignition OFF.
- Disconnect: Engine Oil Pressure Switch C103.
- Connect a fused jumper wire between the engine oil pressure switch C103-1, circuit CMC24 (GY), harness side and ground.
- Ignition ON.
- Observe the low oil pressure warning indicator.
- Does the low oil pressure indicator turn off?
Yes
REMOVE the jumper wire. GO to AB7.
No
LEAVE the jumper wire connected. GO to AB6.
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AB6 CHECK THE ENGINE OIL PRESSURE INPUT CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: C175e.
- With the jumper wire in place, measure the resistance between the PCM C175e-24, circuit CMC24 (GY), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
REMOVE the jumper wire. GO to AB8.
No
REMOVE the jumper wire. REPAIR circuit CMC24 (GY) for an open. TEST the system for normal operation.
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AB7 CHECK THE OIL PRESSURE
- Carry out the engine oil pressure test. Refer to Engine System - General Information Oil Pressure Test.
- Is the oil pressure within specification?
Yes
INSTALL a new engine oil pressure switch. REFER to Engine Service and Repair. TEST the system for normal operation.
No
REFER to Engine System - General Information Testing and Inspection to continue diagnosis of the engine oil pressure.
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AB8 RETRIEVE THE RECORDED DTCs FROM THE PCM KOEO SELF-TEST
- Check the recorded PCM DTCs from the Key ON Engine OFF (KOEO) self-test.
- Are any DTCs recorded?
Yes
REFER to Computers and Control Systems. TEST the system for normal operation.
No
GO to AB9.
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AB9 CHECK FOR CORRECT PCM OPERATION
- Disconnect the PCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the PCM connector and make sure it seats correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new PCM. REFER to Electronic Engine Controls Service and Repair. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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