C2.4 Tier 4 Final Engines for Caterpillar Built Machines Caterpillar

NOx Reduction System (NRS) - Test

Usage:

NRS Valve Circuit - Test

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Table 1
Diagnostic Trouble Codes
Code	Description	Conditions	Notes
523574-4	EGR Actuator Coil Short	Battery voltage is normal. EGR actuator coil short error signal received via CAN for 3 seconds or more.	EGR Stop Warning Level 1 Engine Derates 25% Intake Throttle fully open
523572-4	EGR Position Sensor Failure	Battery voltage is normal. EGR position sensor error signal receives via CAN for 3 seconds or more.
523578-2	No communication with EGR	Battery voltage is normal. Starter switch signal is not activated. Interruption of CAN communication for 1.3 seconds or more.

Note: The 523578-2 is also often caused by a harness problem.

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Illustration 1	g06111286

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check the voltage at the EGR connector terminals 3 and 4. A. The voltage should be between 10 and 16 V.	Voltage	Result: If OK, then continue to Test Step 2. Result: If not OK, then fault is in the harness. Replace the engine harness
2. Check Continuity for CAN Communication Circuit Between EGR Connector Terminal and ECM Connector	Continuity	Result: If NOT OK, then replace the engine harness. Result: If OK, then replace the EGR valve. If this is an intermittent issue, it is likely a harness. Thoroughly inspect the harness before replacing the intake throttle.

Note: After repairing, run the engine until the coolant temp is above 65° C (149° F) to ensure that no diagnostic codes are created. Then perform an “EGR Valve Control Override” test in ET.

NRS Valve Test

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Table 3
Diagnostic Codes
Code	Description	Conditions Present	Response
523572-4	EGR Position Sensor Failure	Battery voltage normal EGR control line is normal EGR position sensor error signal received via CAN for 3 seconds or more.	Engine derates 25% EGR stops Warning Level 2
523574-3	EGR Actuator Open Circuit	Battery voltage is normal. EGR actuator open error signal received via CAN for 3 seconds or more.
523574-4	EGR Actuator Coil Short
523575-7	EGR Actuator Valve Stuck
523576-2	EGR Motor Overheat
523577-2	EGR Motor Temperature Sensor Failure

Note: These diagnostic codes are detecting internal failures of the EGR.

Note: If code 523578-2 code is active. Resolve this code first.

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Table 4
Troubleshooting Test Steps	Values	Results
1. Perform EGR Valve Control Override test in Cat ET	EGR Valve Control Override	Result: If OK, then EGR is operating normally. Result: If NOT OK, then replace the EGR valve

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).