Pinpoint Tests AH: The Low Oil Pressure Message Center Warning Indicator Is Never/Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test AH: The Low Oil Pressure Message Center Warning Indicator Is Never/Always On
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 IPC uses both the messaged oil pressure status and engine rpm to control the low oil pressure message center warning indicator. The PCM provides a reference voltage to the engine oil pressure switch when the ignition key is in the RUN position. With the engine running and 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 active (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:
- Message center concern
- Wiring, terminals or connectors
- Tachometer concern
- Engine oil pressure switch
- Base engine oil pressure concern
- PCM
PINPOINT TEST AH: THE LOW OIL PRESSURE MESSAGE CENTER WARNING INDICATOR IS NEVER/ALWAYS ON
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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AH1 VERIFY THE OPERATION OF THE TACHOMETER
- Ignition ON.
- With the engine running, verify the tachometer is operating correctly.
- Does the tachometer operate correctly?
Yes
GO to AH2.
No
For an inoperative gauge, GO to Pinpoint Test J. For an incorrect gauge, GO to Pinpoint Test K. Pinpoint Test J: The Tachometer Is Inoperative Pinpoint Test K: Incorrect Tachometer Indication
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AH2 VERIFY THE OPERATION OF THE DOOR AJAR MESSAGE CENTER WARNING INDICATOR
- Close all doors then open the LH front door.
- NOTE: If multiple warnings are present, the message center cycles through each of the warnings. Allow the displays to cycle through each display while determining whether the door ajar message center warning indicator is active.
- Observe the message center.
- Is the door ajar message center warning indicator active?
Yes
If the low oil pressure message center warning indicator is never on, GO to AH3. If the low oil pressure message center warning indicator is always on, GO to AH5.
No
GO to Pinpoint Test AN. Pinpoint Tests AN: The Door Ajar Message Center Warning Indicator Is Never/Always On
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AH3 CHECK FOR A STUCK CLOSED ENGINE OIL PRESSURE SWITCH
- Ignition OFF.
- Disconnect: Engine Oil Pressure Switch C103.
- Start the engine.
- Observe the low oil pressure warning indicator.
- Does the low oil pressure warning indicator turn on?
Yes
INSTALL a new engine oil pressure switch. REFER to Engine Service and Repair or Electronic Engine Controls - Diesel Engine . TEST the system for normal operation.
No
GO to AH4.
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AH4 CHECK THE OIL PRESSURE INPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: PCM C175e (Gasoline) or C1232e (Diesel).
- For gasoline engines, measure the resistance between the PCM C175e-24, circuit CMC24 (GY), harness side and ground.
- For the diesel engine, measure the resistance between the PCM C1232e-56, circuit CMC24 (GY), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to AH9.
No
REPAIR circuit CMC24 (GY) for a short to ground. TEST the system for normal operation.
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AH5 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 AH6.
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AH6 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.
- Start the engine.
- Observe the low oil pressure warning indicator.
- Does the low oil pressure indicator turn off?
Yes
REMOVE the jumper wire. GO to AH8.
No
LEAVE the jumper wire connected. GO to AH7.
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AH7 CHECK THE ENGINE OIL PRESSURE INPUT CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: C175e (Gasoline) or C1232e (Diesel).
- For gasoline engines, measure the resistance between the PCM C175e-24, circuit CMC24 (GY), harness side and ground.
- For the diesel engine, measure the resistance between the PCM C1232e-56, circuit CMC24 (GY), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
REMOVE the jumper wire. GO to AH9.
No
REMOVE the jumper wire. REPAIR circuit CMC24 (GY) for an open. TEST the system for normal operation.
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AH8 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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AH9 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 AH10.
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AH10 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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