C27 and C32 Engines for Caterpillar Built Machines Caterpillar

The NRS is used to introduce a controlled amount of exhaust gas into the intake air supply of the engine. The introduction of this inert gas into the combustion air helps to reduce the temperatures and pressures that are created during combustion. The emissions levels of the engine are reduced.

The NRS consists of the following components:

• Absolute pressure sensor

• Cooler

• Differential pressure sensor

• Temperature sensor

• Solenoid for the valve actuator

• Valve

• Venturi

The following diagnostic trouble codes aid in detection of pressure and air flow issues within the NRS.

Table 1

CDL Code	Code Description	Comments
3405-5	Engine Exhaust Gas Recirculation Valve Control : Current Below Normal	The Electronic Control Module (ECM) detects a low current in the circuit for the NRS actuator solenoid.
3405-6	Engine Exhaust Gas Recirculation Valve Control : Current Above Normal	The ECM detects a high current in the circuit for the NRS actuator solenoid.
E1090(2)	High Engine Exhaust Gas Recirculation Intake Pressure	The ECM detects an abnormally high inlet pressure to the NRS.
E1093(2)	Low Engine Exhaust Gas Recirculation Differential Pressure	The ECM detects an abnormally low reading from the NRS differential pressure sensor.
E1094(2)	High Engine Exhaust Gas Recirculation Differential Pressure	The ECM detects an abnormally high reading from the NRS differential pressure sensor.
E1095(1)	Low Engine Exhaust Gas Recirculation Flow Rate	The ECM has detected a low flow rate through the NRS.
E1095(2)	Low Engine Exhaust Gas Recirculation Flow Rate	The ECM has detected a low flow rate through the NRS.
E1096(1)	High Engine Exhaust Gas Recirculation Flow Rate	The ECM has detected a high flow rate through the NRS.
E1096(2)	High Engine Exhaust Gas Recirculation Flow Rate	The ECM has detected a high flow rate through the NRS.

Table 2

Associated Code
CDL Code	WCI
E1092	(2)

Illustration 1	g02138942
Location of the NRS actuator solenoid

Note: Exhaust Gas Recirculation (EGR) is a term used to describe the recirculation of exhaust gas through the engine as a means to reduce "NOx" emissions. Caterpillar has elected to refer to this system as the NO_X Reduction System (NRS). Diagnostic codes are regulated by SAE. The diagnostic codes will reflect the EGR nomenclature.

Illustration 2	g02138941
Schematic for the NRS actuator solenoid

Table 3

Troubleshooting Test Steps	Values	Results
1. Perform Pressure Sensor Calibration A. Connect Cat® Electronic Technician (ET) to the service tool connector. B. Turn the keyswitch to the ON position. Allow 30 seconds for a calibration of the engine pressure sensors to be performed by the ECM. C. Check for diagnostic trouble codes that are associated with the sensor calibration. D. Turn the keyswitch to the OFF position.	Codes	Result: There are no active -13 codes currently. Proceed to Test Step 2. Result: Either a 1785-13, or a 3387-13 is active. Repair: Perform another calibration attempt, follow these instructions closely: 1. Turn the keyswitch to the OFF position. Allow the keyswitch to remain in the OFF position for ten minutes. 2. Turn the keyswitch to the ON position. Allow 30 seconds for the ECM to attempt a calibration of the sensor. 3. Turn the keyswitch to the OFF position. Allow the keyswitch to remain in the OFF position for 30 seconds. Note: Do not use the battery disconnect switch to power-down the ECM. Ensure that the unswitched battery power to the ECM remains on so that the calibration data can be saved to internal memory. 4. Turn the keyswitch to the ON position. Check for diagnostic trouble codes that are associated with the sensor calibration. If the original code is still active, replace the appropriate sensor. Check for the recurrence of the diagnostic codes to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 2.
2. Check for Associated Codes A. Establish communication between Caterpillar Electronic Technician (ET) and the service tool connector. B. Determine if an associated code is active or logged.	Associated Codes	Result: No associated codes are active or logged. Proceed to Test Step 3. Result: There are associated codes that are active or logged. Repair: Troubleshoot associated codes prior to continuing with this procedure. Refer to Troubleshooting, "Event Codes" to troubleshoot the associated diagnostic code. If the problem is not resolved, proceed to Test Step 3.
3. Check for Codes A. Connect Cat Electronic Technician (ET) to the service tool connector. B. Determine if a code is active or logged.	Codes	Result: A 3405-5 code is active. Proceed to Test Step 13. Result: A 3405-6 is active. Proceed to Test Step 12. Result: A E1090(2) is logged or active. Proceed to Test Step 6. Result: A E1090(2) and E1095(2) are active or logged. Proceed to Test Step 6. Result: E1090(2) and/or E1093(2) and/or E1094(2) is active or logged. Proceed to Test Step 8. Result: E1095(2) and/or E1096(2) is active or logged. Proceed to Test Step 4.

Illustration 3	g02149542
Inspection points for the exhaust piping for the NRS that is on the top of the engine

Table 4

Troubleshooting Test Steps	Values	Results
4. Inspect all Exhaust Piping for the NRS for Leakage A. Inspect all exhaust piping for the NRS for signs of leakage. Thoroughly inspect the following components of the NRS for leakage: · Exhaust manifold · Connections for the exhaust flanges · Exhaust manifold bellows for the exhaust inlet and exhaust outlet for the NRS cooler · Exhaust bellows for the NRS manifold on the top of the engine · Inlet and outlet connections for the NRS venturi · Connections for the NRS · Connections for the NRS to the air inlet piping · Inlet and outlet connections for the NRS actuator and valve assembly Note: Common indications of a leak in the NRS are a loose connection, a damaged line, or a buildup of soot in the critical components.	Leakage of Exhaust Piping for the NRS	Result: The exhaust piping for the NRS is not leaking. Proceed to Test Step 6. Result: A leak has been discovered in the piping for the NRS. Repair: Repair the leaks. Clear all diagnostic codes and use Cat ET to perform an "EGR Service Test" to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 5.

Illustration 4	g02127353
Location of the components for the NRS (1) Temperature sensor for the NRS (2) Solenoid for the NRS actuator (3) Steel tubing for the pressure sensors that are for the NRS (4) Differential pressure sensor for the NRS (5) Absolute pressure sensor for the NRS

Table 5

Troubleshooting Test Steps	Values	Results
5. Inspect all Components of the NRS for Leakage A. Inspect the condition of the following components for the NRS: · Temperature sensor · Solenoid and actuator · Steel tubing for the pressure sensors · Differential pressure sensor · Absolute pressure sensor Check each of the components for visible signs of exhaust leakage. Ensure that the components are in good repair and check that the components are securely mounted. Note: Common signs of a leak in the NRS are loose connections, damaged lines, or a buildup of soot in critical components.	Leakage	Result: The components for the NRS are not leaking. Proceed to Test Step 6. Result: leak has been discovered or one of the NRS components has visible signs of damage. Repair: Perform any necessary repairs. Clear all diagnostic codes and use Cat ET to perform an "EGR Service Test" to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 6.

Table 6

Troubleshooting Test Steps	Values	Results
6. Use Cat ET to Perform an "EGR Service Test" A. Start the engine. B. Connect Cat ET to the service tool connector. Establish a connection to the engine ECM. C. Select the "Diagnostics" drop-down menu. D. Select the "Diagnostics Tests" from the menu. E. Select the "EGR Service Test". Once "EGR Service Test" is selected, follow the instructions on the display screen to run the test.	EGR Service Test	Result: The "EGR Service Test" completes successfully. Repair: Contact your Technical Communicator for additional information. Result: The "EGR Service Test" fails due to "Delivered Fuel Volume Not Responding". When the NRS gas flow is being commanded to change, no change in fuel delivery was measured. Increasing the NRS gas flow or decreasing the NRS gas flow will impact the amount of fuel needed to maintain the desired engine speed. Proceed to Test Step 7. Result: The "EGR Service Test" fails due to "EGR Delta Pressure Not Responding". When the NRS valve is commanded from the OPEN position to the CLOSED position, no change in NRS delta pressure is detected. Proceed to Test Step 8. Result: The "EGR Service Test" fails due to "EGR Absolute Pressure Not Responding" and/or "EGR Delta Pressure Not Responding". This fault indicates that when the NRS valve is commanded to reposition, the NRS intake pressure and/or the NRS differential pressure does not change. Proceed to Test Step 9. Result: The "EGR Service Test" fails due to "EGR Mass Flow Rate Incorrect". The fault indicates that when the NRS valve is commanded to reposition, the desired NRS mass flow does not match the actual mass flow rate. Proceed to Test Step 10.

Illustration 5	g02127653
Shaft for the NRS valve

Table 7

Troubleshooting Test Steps	Values	Results
7. Check the NRS Valve Assembly for Smooth Operation A. Remove the actuator assembly from the NRS valve body. Use a straight screwdriver to rotate the shaft of the butterfly valve inside the valve body. The valve must rotate freely from the OPEN position to the CLOSED position. The shaft will rotate for a total of 90 degrees.	NRS Valve Assembly	Result: The shaft of the NRS valve rotates freely from the OPEN position to the CLOSED position. Repair: There is a problem with the NRS actuator. Install a new actuator assembly to the valve body. Clear all diagnostic codes. Use Cat ET to perform an "EGR Service Test" to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 8. Results: The shaft of the NRS valve does not rotate freely, or the shaft does not rotate. Repair: Replace the NRS valve body. Reinstall the actuator assembly that was previously removed. Clear all diagnostic codes. Use Cat ET to perform an "EGR Service Test" to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 8.

Illustration 6	g02127693
Passages for the NRS pressure sensors

Table 8

Troubleshooting Test Steps	Values	Results
8. Inspect the Passages and Steel Tubing for the Differential Pressure Sensor for Plugging A. Remove the steel tubing, the mounting block, the NRS differential pressure sensor, and the absolute pressure sensor. B. Check the steel tubing for a buildup of exhaust soot. If necessary, use compressed air to check the steel lines for plugging. If a buildup of soot is found in the tubing, you may expect further buildup in the mounting block for the sensors. C. Inspect the passages in the mounting block for the sensors for a buildup of exhaust soot. Also, inspect the differential pressure sensor and the absolute pressure sensor for plugging due to an accumulation of exhaust soot.	Differential Pressure Sensor	Result: There is little or no soot build-up evident. Repair: The differential pressure sensor for the NRS is not reading the pressure correctly. Replace the differential pressure sensor. Clear all diagnostic codes. Use Cat ET to perform an "EGR Service Test" to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 9. Result: Soot buildup is evident in the components of the NRS differential pressure sensors. Repair: Remove the NRS venturi. Clean the following components: · Passages of the NRS venturi · Steel tubing · Mounting block for the sensors · Differential pressure sensor · Absolute pressure sensor Replace parts, if necessary. Clear all diagnostic codes. Use Cat ET to perform an "EGR Service Test" to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 9.
9. Inspect the Passages and Steel Tubing for the NRS Pressure Sensors for Plugging A. Remove the steel tubing, the mounting block, the NRS differential pressure sensor, and the absolute pressure sensor. B. Check the steel tubing for a buildup of exhaust soot. If necessary, use compressed air to check the steel lines for plugging. If a buildup of soot is found in the tubing, you may expect further buildup in the mounting block for the sensors. C. Inspect the passages in the mounting block for the sensors for a buildup of exhaust soot. Also, inspect the differential pressure sensor and the absolute pressure sensor for plugging due to an accumulation of exhaust soot.	NRS Pressure Sensors	Result: Little or no soot buildup is evident. Repair: The absolute pressure sensor and the differential pressure sensor for the NRS are not reading the pressure correctly. Replace the differential pressure sensor and the absolute pressure sensor. Clear all diagnostic codes. Use Cat ET to perform an "EGR Service Test" to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 10. Result: Soot buildup is evident in the components of the NRS differential pressure sensors. Repair: Remove the NRS venturi. Clean the following components: · Passages of the NRS venturi · Steel tubing · Mounting block for the sensors · Differential pressure sensor · Absolute pressure sensor Replace parts, if necessary. Clear all diagnostic codes. Use Cat ET to perform an "EGR Service Test" to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 10.
10. Use Cat ET to Check for Active Codes A. Establish a connection between the engine ECM and Cat ET. B. Check for diagnostic codes that are active or logged. Check for codes that became active during the "EGR Service Test".	Codes	Result: No codes are generated. Proceed to Test Step 11. Result: 3386-3 or 3386-4 is active. Repair: There is an electrical problem in the circuit for the NRS temperature sensor. There may be a problem with the sensor. Refer to Troubleshooting, "Sensor Signal (Analog, Passive) - Test" for information that is related to troubleshooting the problem. If the problem is not resolved, proceed to Test Step 11.
11. Inspect the NRS Valve A. Remove the actuator assembly from the NRS valve body. Use the appropriate screwdriver to rotate the valve inside the NRS valve body. The valve should freely rotate from OPEN to CLOSED for 90 degrees of rotation.	NRS Valve	Result: NRS valve does not rotate at all, or the valve is difficult to rotate. Repair: Replace the NRS valve body. Install the actuator assembly that was previously removed. Clear all diagnostic codes and use Cat ET to perform an "EGR Service Test" to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 12. Result: The NRS valve does rotate freely through all 90 degrees of rotation. Repair: Install a new actuator assembly. Clear all diagnostic codes and use Cat ET to perform an "EGR Service Test" to verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 12.
12. Create an Open Circuit at the Harness Connectors for the NRS Actuator Solenoid A. Remove electrical power from the ECM. B. Disconnect the connectors for the NRS actuator solenoid. C. Restore the electrical power to the ECM. Note: The ECM can only detect an open circuit condition on this circuit when the output driver is not activated. D. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. E. Remove electrical power from the ECM. Leave the connectors for the NRS actuator solenoid disconnected.	Open Circuit	Result: The active code changed from a -6 code to a -5 code. Repair: The circuit for the solenoid is OK. There is a problem with the solenoid. Temporarily connect a new solenoid to the harness, but do not install the new solenoid. Verify that there are no active codes for the NRS actuator solenoid. If there are no active codes for the NRS, permanently install the new solenoid. Clear any logged diagnostic codes. If the problem is not resolved, proceed to Test Step 13. Result: The -6 code remains active while both of the connectors are disconnected. The short is in the harness between the connector for the solenoid and the ECM. There may be a problem with the ECM. Leave the connectors for the solenoid disconnected. Proceed to Test Step 14.
13. Create a Short Circuit at the Connectors for the NRS Actuator Solenoid A. Remove electrical power from the ECM. B. Fabricate two jumper wires that are long enough to create a short circuit across the solenoid connectors. Crimp connector pins to each end of the jumper wire. C. Install a jumper wire across terminal 1 (solenoid signal) and terminal 2 (return) of the harness connector for the NRS actuator solenoid. D. Restore the electrical power to the ECM. E. Proceed to the "Diagnostic Overrides" screen on Cat ET. F. Activate the "EGR Valve Control Override". The system will activate for ten seconds. Note: The ECM can only detect a short circuit condition on this circuit when the output driver is activated. G. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. A -6 code will be active for the solenoid. H. Remove electrical power from the ECM.	Short Circuit	Result: A -5 code was active before the jumper wire was installed. A -6 code became active after the jumper wire was installed. Repair: The NRS actuator solenoid has an open circuit in the windings of the solenoid. Replace the faulty solenoid. If the problem is not resolved, proceed to Test Step 14. Result: A -5 code was active before the jumper wires were installed. The -6 code did not become active after the jumper wires were installed. The open is in the harness wiring between the connector for the NRS actuator solenoid and the ECM. There may be a problem with the ECM. Proceed to Test Step 14.
14. Check the Operation of the ECM A. Remove electrical power from the ECM. B. Disconnect the J2/P2 ECM connectors. C. Fabricate two jumper wires that are long enough to create a test circuit across the ECM connector. Crimp a connector socket to one end of each of the jumper wires. D. Install the jumper wires into terminal locations P2-44 (solenoid signal) and P2-32 (return). E. Connect the J2/P2 connectors. F. Check the operation of the ECM by creating an open at the ECM: G. Check the operation of the ECM by creating a short at the ECM: A -6 code will become active for the NRS actuator solenoid with the short circuit in place. H. Remove electrical power from the ECM. I. Return all wiring to the original configuration.	Operation of the ECM	Result: A -5 code is active when the circuit is open. A -6 code is active when the jumper wires are shorted. Repair: The ECM is operating properly. The problem is in the wiring between the ECM and the NRS actuator solenoid. Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminated the problem. Result: One of the following conditions exists: A -5 code is not active when the jumper wires are open. A -6 code is not active when the wire jumpers are shorted. Repair: The ECM does not detect the open circuit or the short circuit at the ECM connector. There is a problem with the ECM. Perform the following procedure: 1. Temporarily connect a test ECM. Refer to Troubleshooting, "ECM - Replace". 2. Recheck the circuit to ensure that the original problem has been resolved. If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved. If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring. Verify that the repair eliminated the problem.