C11, C13, C15, and C18 Industrial Engines Caterpillar

The exhaust gas that flows from the exhaust manifold is mixed with fresh air. The NRS meters the mixture of air and exhaust. The NRS also cools the mixture. This mixture will reduce the NOx emissions of the engine.

The following NRS consists of the following components:

• NRS cooler

• NRS venturi

• NRS absolute pressure sensor

• NRS differential pressure sensor

• NRS temperature sensor

• NRS valve

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

Note: Some of the following codes may not be applicable for certain applications.

Table 1

Diagnostic Trouble Codes
CDL Code	J1939 Code	Code Description (code descriptions may vary)	Comments
E1090 (2)	3358-16	High EGR Intake Pressure	The ECM detects a higher than desired EGR Intake Pressure
E1095 (1)	2659-17	Low EGR Mass Flow Rate	The Electronic Control Module (ECM) detects a lower than desired flow rate through the NRS
E1096 (1)	2659-15	High EGR Mass Flow Rate	The ECM detects a higher than desired flow rate through the NRS
E1093 (1)	411-17	Low EGR Differential Pressure	The ECM detects an abnormally low reading from the NRS differential pressure sensor.
E1094 (1)	411-15	High EGR Differential Pressure	The ECM detects an abnormally high reading from the NRS differential pressure sensor.

Note: EGR is an industry standard 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 "NOx Reduction System" (NRS). Diagnostic codes are regulated by SAE, therefore, the diagnostic codes still reflect the EGR nomenclature.

Table 2

Associated Diagnostic Trouble Codes
E1154
E1123
E1092
3609-17
3609-18
5276-7
412-15
412-16

Table 3

Troubleshooting Test Steps	Values	Results
1. Check for Diagnostic Trouble Codes A. Establish communication between Cat® Electronic Technician (ET) and the ECM . Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Troubleshoot any active or logged diagnostic trouble codes before troubleshooting the event codes outlined in this procedure. Determine if an associated code is active or logged. Table 2 lists associated diagnostic codes.	Associated Codes	Result: There are associated codes. Refer to Troubleshooting, "Event Codes" in order to troubleshoot the associated diagnostic code. Result: There are no associated codes. If the original diagnostic trouble code was a E1095, E1096, 2659-15 and/or a 2659-17. Proceed to Test Step 2. Result: There are no associated codes. If the original diagnostic trouble code was a E1093, E1094, 411-17 and/or 411-15. Proceed to Test Step 5. Result: There are no associated codes. If the original diagnostic trouble code was a E1090 and/or 3358-16. Proceed to Test Step 3.

Illustration 1	g03781036
Inspection points for the left side of the engine (1) NRS inlet valve (2) NRS temperature sensor (3) NRS outlet valve

Illustration 2	g03781037
Inspection points for the right side of the engine (4) NRS cooler outlet (5) NRS cooler inlet (6) NRS bellows joint

Table 4

Troubleshooting Test Steps	Values	Results
2. Inspect the NRS for Leakage A. Inspect the following components of the NRS for leakage: · Exhaust manifold · Connections for NRS cooler inlet and NRS cooler outlet · NRS venturi inlet and outlet connections · Port locations for NRS differential pressure sensor and NRS absolute pressure sensor · Connections for NRS inlet valve and NRS outlet valve Common signs of a leak in the NRS are loose connections, damaged lines, or components and exhaust soot buildup around the area that is leaking.	Leakage	Result: Leaks were found in the system. Repair: Repair the leaks. Reset all active codes and clear all logged codes. Use Cat ET to perform an "EGR System Test" in order to verify that the problem is resolved. Result: Leaks were not found in the system. Proceed to Test Step 3.
3. Use Cat ET to Perform an "EGR System Test" A. Start the engine. B. Use Cat ET to perform an "EGR System Test".	Test	Result: The "EGR System 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 or decreasing the NRS gas flow will impact the amount of fuel needed to maintain the desired engine speed. Proceed to Test Step 4. Result: The "EGR System Test" fails due to "EGR Delta Pressure Not Responding". The fault indicates that when the NRS valve moves from open to closed, no change in NRS delta pressure is measured. Proceed to Test Step 5. Result: The "EGR System Test" fails due to "EGR Absolute Pressure Not Responding". The fault indicates that when the NRS valve moves from open to closed, no change in the NRS absolute pressure is measured. Proceed to Test Step 6. Result: The "EGR System Test" fails due to "EGR Mass Flow Rate Incorrect". The fault indicates when the NRS valve moves from open to closed, the desired NRS mass flow is different from the actual mass flow rate. Proceed to Test Step 4.

Illustration 3	g03781041
NRS valve (7) NRS actuator assembly (8) NRS valve body

Illustration 4	g03781337
NRS valve (9) Point of rotation

Table 5

Troubleshooting Test Steps	Values	Results
4. Inspect the NRS Valve A. Remove actuator assembly from NRS valve body. B. Use a straight screwdriver to rotate the valve inside the NRS valve body. The valve should freely rotate from the open to close positions for 90 degrees of rotation.	Valve Rotates Freely	Result: NRS valve does not rotate at all, or the valve is difficult to rotate. Repair: Replace the NRS valve body and install the actuator assembly that was previously removed. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Use Cat ET to perform an "EGR System Test" in order to verify that the problem is resolved. Result: NRS valve does rotate freely from open to close. Repair: Install new actuator assembly. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Use Cat ET to perform an "EGR System Test" in order to verify that the problem is resolved.

Illustration 5	g03781343
Typical mounting locations for the NRS sensors (10) NRS differential pressure sensor (11) NRS absolute pressure sensor (12) Mounting point for NRS differential pressure sensor

Table 6

Troubleshooting Test Steps	Values	Results
5. Inspect the Mounting Location for the NRS Differential Pressure Sensor A. Refer to Troubleshooting, "Electrical Connectors - Inspect" when checking sensors. B. Remove the NRS differential pressure sensor. C. Inspect the mounting location for signs of accumulations of soot. The accumulation may indicate further accumulations of soot downstream in the pressure passages.	Soot Build-Up	Result: Soot build-up is evident in the NRS differential pressure sensor passages. Repair: Remove the NRS venturi. Use hot soapy water and a bore brush to clean out the passages for the NRS venturi differential pressure. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Use Cat ET to perform an "EGR System Test" in order to verify that the problem is resolved. Result: Little or no soot build-up evident. Repair: Replace the NRS differential pressure sensor. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Use Cat ET to perform an "EGR System Test" in order to verify that the problem is resolved.

Illustration 6	g03781358
Typical mounting locations for the NRS sensors (13) NRS differential pressure sensor (14) NRS absolute pressure sensor (15) Mounting point for NRS absolute pressure sensor

Table 7

Troubleshooting Test Steps	Values	Results
6. Inspect the NRS Absolute Pressure Sensor and the Mounting Location A. Refer to Troubleshooting, "Electrical Connectors - Inspect" when checking sensors. B. Remove the NRS absolute pressure sensor. C. Visually inspect all of the mounting locations for signs of excessive soot. The excessive soot may indicate further buildup downstream in the pressure passages.	Soot Build-Up	Result: Soot build-up is evident in the absolute pressure sensor passage. Repair: Remove the NRS venturi. Use hot soapy water and a bore brush to clean the passages. Install the NRS venturi. Reset all active codes and clear all logged codes. Use Cat ET to perform an "EGR System Test" in order to verify that the problem is resolved. Result: Little or no soot build-up evident. Repair: Replace the NRS absolute pressure sensor. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Use Cat ET to perform an "EGR System Test" in order to verify that the problem is resolved.

Contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).