FAULT CODE 143

Oil Pressure – Engine Protection

Overview

CODE	REASON	EFFECT
Fault Code: 143 PID: P100 SPN: 100 FMI: 1 LAMP: Engine Protection or Red SRT: 00-057	Low oil pressure has been detected. Voltage at oil pressure signal pin 7 of the sensor harness connector indicates oil pressure lower than 55 kPa [8 psi] at idle to 800 rpm; 55 to 173 kPa [8 to 25 psi] at 800 to 1200 rpm; 173 to 208 kPa [25 to 30 psi] at 1200 to 2400 rpm for M11; 138 to 208 kPa [20 to 30 psi] at 1200 to 2400 rpm for N14.	Progressive power and speed derate with increasing time after alert. If Engine Protection Shutdown is enabled, engine will shut down 30 seconds after the engine protection lamp or the Red lamp* starts flashing.

Oil Pressure Sensor Circuit

SMALL | MEDIUM | LARGE

Circuit Description

The electronic control module (ECM) uses the oil pressure sensor to monitor the lubricating oil pressure. The ECM converts the signal pin voltage to a pressure value. The ECM uses this value for the engine protection system.

Component Location

• M11 – The oil pressure sensor is located on the engine block to the right of the ECM.
• 1994 N14 – The oil pressure sensor is on the engine block, near the pan rail, on the fuel pump side of the engine.
• 1991 N14 – The oil pressure sensor is on the engine block, above the fuel supply pump.

Shop Talk

• Verify with the driver the engine speed at which the fault occurs. If the engine is operated at too low of a speed under load, oil pressure can drop below the engine protection limits.
• Use breakout cable, Part Number 3824775, between the oil pressure sensor and the sensor connector, keyswitch ON and oil pressure sensor connected and disconnected; confirm the supply voltage is 4.75 to 5.25 VDC.
• *Applies to 98N14 and 98M11 calibrations only.

Troubleshooting Steps

STEPS		SPECIFICATIONS
STEP 1.	Check the sensor accuracy.
	STEP 1A. Verify the sensor accuracy with a mechanical gauge.	Sensor reading is correct
STEP 2.	Clear the fault codes.
	STEP 2A. Disable the fault code.	Fault Code 143 inactive
	STEP 2B. Clear the inactive fault codes.	All fault codes cleared

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Guided Step 1 – Check the sensor accuracy.

Guided Step 1A – Verify the sensor accuracy with a mechanical gauge.
Conditions Turn keyswitch ON. Action Connect a mechanical oil pressure gauge to the engine. Connect INSITE™ electronic service tool to the vehicle datalink. Start the engine and compare the oil pressure reading on the service tool monitor screen with the reading on the mechanical oil pressure gauge. Note: If necessary, increase the engine speed to make it easier to see differences in the readings.
OK	NOT OK
The sensor reading is correct Refer to the Troubleshooting and Repair Manual, M11 Series Engines (STC, CELECT™, CELECT™ Plus models), Bulletin 3666139. Refer to the Troubleshooting and Repair Manual, N14 Series Engines (STC, CELECT™, CELECT™ Plus models), Bulletin 3666142.	Does not meet specifications.
Go to 2A	Fault Code 141

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Guided Step 2 – Clear the fault codes.

Guided Step 2A – Disable the fault code.
Conditions Connect all the components. Action Start the engine and let it idle for one minute. Note: If the fault was at a particular speed, run the engine at that speed to verify the problem is corrected. Verify Fault Code 143 is inactive.
OK	NOT OK
Fault Code 143 inactive	Fault Code 143 active. Return to the troubleshooting steps or contact your nearest Cummins Authorized Repair Location if all the steps have been completed and checked again.
Go to 2B	Go to 1A

Guided Step 2B – Clear the inactive fault codes.
Conditions Connect all the components. Action Erase inactive fault codes using INSITE™ electronic service tool.
OK	NOT OK
All fault codes cleared	Troubleshoot any remaining active fault codes.
Repair complete	Appropriate troubleshooting chart