C7.1 Industrial Engine and Generator Set Caterpillar


NRS Mass Flow Rate Problem

Usage:

C7.1 770
System Operation Description:

This procedure covers the following diagnostic trouble code:

Table 1
Diagnostic Trouble Code for NRS Mass Flow Rate Problem 
J1939 Code  Code Description  Comments 
2659-7  Engine Exhaust Gas Recirculation (EGR) Mass Flow Rate : Not Responding Properly  Actual mass flow through the NOx Reduction System (NRS) does not match the desired mass flow.
The Electronic Control Module (ECM) has been powered for at least 2 seconds.
The engine is running.
There are no active codes for the 5 VDC supply.
There are no active 27, 157, 411, 1188, 2791, 3358 or 3563 codes.
412-3 or 412-4 codes are not active.
3464-7 code is not active. 


Illustration 1g02160656
(1) Manifold for the NRS pressure sensors
(2) NRS differential pressure sensor
(3) NRS inlet pressure sensor
(4) Pipe for the NRS inlet pressure sensor
(5) Pipe for the NRS differential pressure sensor
(6) NRS inlet temperature sensor
(7) NRS mixer

Test Step 1. Check for Associated Diagnostic Trouble Codes

  1. Establish communication between the electronic service tool and the ECM . If necessary, refer to Troubleshooting, "Electronic Service Tools".

  2. Check for diagnostic trouble codes that are associated with the NRS valve or the inlet throttle valve. Troubleshoot NRS valve and inlet throttle valve faults before continuing with this procedure.

  3. Determine if associated code 3609-17 is active or logged. If code 3609-17 is active or recently logged, troubleshoot that code before continuing with this procedure.

Results:

  • Diagnostic code 3609-17 is active or logged. -

    Repair: Refer to Troubleshooting, "Diagnostic Trouble Codes" to troubleshoot the associated diagnostic code.

    STOP

  • There are no associated codes. - Proceed to Test Step 3.

Test Step 2. Inspect the Electrical Connectors and the Harness

  1. Turn the keyswitch to the OFF position.

  2. Inspect the connectors for the components in the NRS system. Refer to Troubleshooting, "Electrical Connectors - Inspect".

  3. Perform a 45 N (10 lb) pull test on each of the wires in any suspect connector and the connections at the ECM.

  4. Check that the ground connection on the ECM and the negative terminal on the battery are correctly installed.

  5. Check the ground connection on the ECM for abrasions and pinch points.

  6. Check the screws for the ECM connector for the correct torque of 6 N·m (53 lb in).

  7. Check the harness for abrasion and pinch points from the NRS components to the ECM.

  8. Check that any suspect connector is installed correctly.

Expected Result:

The electrical connectors and the cables are correctly installed.

Results:

  • The harness is OK. - Proceed to Test Step 3.

  • Not OK -

    Repair: Repair the faulty connectors or the harness and/or replace the faulty connectors or the harness. Ensure that all the seals are correctly in place and ensure that the connectors are correctly coupled.

    Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair has eliminated the fault.

    STOP

Test Step 3. Check the Air Inlet and Exhaust System

  1. Check the air inlet system for leaks and for restrictions.

  2. Check the exhaust system for leaks and for restrictions.

Results:

  • There are no leaks in the air inlet system or the exhaust system. - Proceed to 4.

  • The air inlet system has a leak or is restricted. -

    Repair: Perform the following procedure:

    1. Clear any restrictions in the air inlet system.

    2. Repair any air leaks in the air inlet system.

    3. Check that the fault has been eliminated.

    If the fault is still present, proceed to Test Step 4.

  • The exhaust system has a leak or is restricted. -

    Repair: Perform the following procedure:

    1. Clear any restrictions in the exhaust system.

    2. Repair any leaks in the exhaust system.

    3. Check that the fault has been eliminated.

    If the fault is still present, proceed to Test Step 4.

Test Step 4. Check the NRS Sensor Pipes

During this procedure, refer to Illustration 1.

  1. Check pipe (4) for the NRS inlet pressure sensor for leaks, restrictions, or blockage.

  2. Check pipe (5) for the NRS differential pressure sensor for leaks or any restriction.

Results:

  • There are no leaks, restrictions, or blockages in the sensor pipes. - Proceed to Test Step 6.

  • There is a leak, a restriction, or a blockage in one of the sensor pipes. -

    Repair: Perform the following repair:

    1. If a pipe has a leak or a restriction, replace the pipe.

    2. If the pipe is blocked with soot or condensate, remove the pipe and clear the blockage with an air line that is set at a maximum pressure of 200 kPa (29 psi). If the blockage is cleared, install the pipe. If the blockage cannot be cleared, replace the pipe.

    3. Check that the fault has been eliminated.

    If the fault is still present, proceed to Test Step 6.

Test Step 5. Check the NRS PRESSURE Sensors

During this procedure, refer to Illustration 1.

  1. Remove NRS differential pressure sensor (2) and NRS inlet pressure sensor (3) from NRS mixer (6). Refer to Disassembly and Assembly.

  2. Check the ports on the sensors for excessive deposits.

Results:

  • The ports on the pressure sensors do not have excessive deposits. - Proceed to Test Step 6.

  • The ports on the pressure sensors have excessive deposits. -

    Repair: Perform the following procedure:

    1. Carefully remove the deposits from the ports on the pressure sensors. Make sure that the ports on the sensors are not damaged.

    2. If the deposits cannot be easily removed, replace the relevant pressure sensor. Refer to Disassembly and Assembly.

    3. Check that the fault has been eliminated.

    If the fault is still present, proceed to Test Step 6.

Test Step 6. Check the NRS Temperature Sensor

During this procedure, refer to Illustration 1.

  1. Remove temperature sensor (7) from NRS mixer (6). Refer to Disassembly and Assembly, "Temperature Sensor (Cooled Exhaust Gas) - Remove and Install".

  2. Check the sensor probe for excessive deposits.

Results:

  • The probe on the temperature sensor does not have excessive deposits. - Proceed to Test Step 7

  • The probe on the temperature sensor has excessive deposits. -

    Repair: Perform the following procedure:

    1. Carefully remove the deposits from the sensor probe. Make sure that the sensor probe is not damaged.

    2. If the deposits cannot be easily removed, replace the temperature sensor. Refer to Disassembly and Assembly, "Temperature Sensor (Cooled Exhaust Gas) - Remove and Install".

    3. Check that the fault has been eliminated.

    If the fault is still present, proceed to Test Step 7.

Test Step 7. Inspect the NRS Mixer

Inspect the NRS mixer for cracks, holes, or damage.

Results:

  • The NRS mixer is defective. -

    Repair: Replace the NRS mixer. Refer to Disassembly and Assembly, "Inlet Air Control - Remove" and Disassembly and Assembly, "Inlet Air Control - Install".

    STOP

  • There are no visible faults on the NRS mixer. - Contact the Technical Communicator at a Caterpillar dealer.

    STOP

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