Pinpoint Tests AA: The Low Oil Pressure Message Center Warning Indicator Is Never/Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test AA: 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). 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 RUN. 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).
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
- Message center concern
- Communication concern
- Tachometer concern
- Engine oil pressure switch
- Base engine oil pressure concern
- PCM
PINPOINT TEST AA: 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.
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AA1 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 AA2.
No
For an inoperative tachometer, GO to Pinpoint Test I Pinpoint Test I: The Tachometer Is Inoperative. For an inaccurate tachometer, GO to Pinpoint Test J. Pinpoint Test J: Incorrect Tachometer Indication
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AA2 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 AA3. If the low oil pressure message center warning indicator is always on, GO to AA5.
No
GO to Pinpoint Test AF. Pinpoint Tests AF: The Message Center Is Not Operating Correctly
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AA3 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 illuminate?
Yes
INSTALL a new engine oil pressure switch. TEST the system for normal operation.
No
GO to AA4.
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AA4 CHECK THE OIL PRESSURE INPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: PCM C175E (3.7L), C1381E (5.0L and 6.2L), or C1551E (3.5L).
- For 3.5L, measure the resistance between the PCM C1551E-9, circuit CMC24 (GY), harness side and ground.
- For 3.7L, measure the resistance between the PCM C175E-13, circuit CMC24 (GY), harness side and ground.
- For 5.0L and 6.2L, measure the resistance between the PCM C1381E-24, circuit CMC24 (GY), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to AA9.
No
REPAIR circuit CMC24 (GY) for a short to ground. TEST the system for normal operation.
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AA5 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 AT. Pinpoint Tests AT: DTC U0100:00
No
GO to AA6.
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AA6 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 AA8.
No
LEAVE the jumper wire connected. GO to AA7.
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AA7 CHECK THE ENGINE OIL PRESSURE INPUT CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: PCM C175E (3.7L), C1381E (5.0L and 6.2L), or C1551E (3.5L).
- For 3.5L, measure the resistance between the PCM C1551E-9, circuit CMC24 (GY), harness side and ground.
- For 3.7L, measure the resistance between the PCM C175E-13, circuit CMC24 (GY), harness side and ground.
- For 5.0L and 6.2L, measure the resistance between the PCM C1381E-24, circuit CMC24 (GY), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
REMOVE the jumper wire. GO to AA9.
No
REMOVE the jumper wire. REPAIR circuit CMC24 (GY) for an open. TEST the system for normal operation.
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AA8 CHECK THE OIL PRESSURE
- Carry out the engine oil pressure test. Refer to Engine System - General Information Testing and Inspection.
- Is the oil pressure within specification?
Yes
INSTALL a new engine oil pressure switch. 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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AA9 RETRIEVE THE RECORDED DTCs FROM THE PCM KOEO SELF-TEST
- Connect: Engine Oil Pressure Switch C103.
- Connect: PCM C175E (3.7L), C1381E (5.0L and 6.2L) or C1551E (3.5L).
- 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 AA10.
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AA10 CHECK FOR CORRECT PCM OPERATION
- Disconnect the PCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the PCM connectors and make sure they seat 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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