Procedure for the Installation of the 372-1187 Nitrogen Oxide Sensor Gp and the 379-0138 Sensor Kit (NITROGEN OXIDE){191N} Caterpillar

Engine:

G3408C (S/N: BAZ1-UP)

G3412C (S/N: 6ZM1-UP)

G3508 (S/N: WPN1-UP)

G3508B (S/N: RBK1-UP)

G3512 (S/N: WPP1-UP; WPR1-UP)

G3512B (S/N: JHH1-UP)

G3516 (S/N: 4EK1-UP; WPT1-UP; WPW1-UP)

G3516B (S/N: JEF1-UP)

G3520B (S/N: GLF1-UP)

Petroleum Engine:

G3520B PETROLEUM (S/N: TPC1-UP)

Introduction

Do not perform any procedure in this Special Instruction until you read and understand the entire procedure.

This Special Instruction provides the procedure to install the 372-1187 Nitrogen Oxide Sensor Group or the 379-0138 Nitrogen Oxide Sensor Kit onto G3400 and G3500 Engines.

Note: If you are replacing the 304-4209 Nitrogen Oxide Sensor Gp , the 379-0138 Sensor Kit (NITROGEN OXIDE) must be used. Due to profile changes in the buffer assembly, the 372-1187 Nitrogen Oxide Sensor Group requires the use of longer button head screws and tube spacers. The 379-0138 Sensor Kit (NITROGEN OXIDE) contains the new sensor group and the necessary mounting hardware.

This procedure also includes the routing and the securing of the new sensor harness. Follow the instructions for securing the harness carefully. Failure to route the harness properly may cause the premature failure of the sensor group.

Required Tools

The following tools are required in order to perform this procedure:

Remove the NO_X Sensor Group

1. Turn the Engine Control Switch (ECS) to the OFF/RESETposition. Use the circuit breaker to remove the power from the Electronic Control Module (ECM).

Show/hide table



Illustration 1	g02606540
NOX sensor and sensor buffer removal (1) Support strap or tie-wrap (2) Tie-wraps (3) Cover (4) Harness connector

2. Remove the sensor and sensor buffer from the engine.

   1. Remove strap (1) .

   2. Carefully remove tie-straps (2) using the diagonal cutters.

   3. Disconnect the engine harness at connectors (4) .

   4. Remove nuts for the cover (3) .

   5. Remove the sensor group.

Install the NO_X Sensor Group

Show/hide table



Illustration 2	g02607344
(6) Holes in the mounting plate (7) Button head screws (8) Sensor buffer (9) Tube spacers (10) Washers (11) Nuts

1. If you are installing the 379-0138 Sensor Kit (NITROGEN OXIDE), install the new button head screws (7) into the mounting plate.

   Note: For some applications the button head screws can be removed through the holes in support bracket (6). For other applications, you may have to remove the mounting plate from the support bracket. If the mounting plate is removed, ensure the proper placement of the rubber grommets and the ground strap when reattaching the plate.

   Torque for button head screws ... 5 ± 2 N·m (4 ± 2 lb ft)

2. Mount sensor buffer (8) onto the mounting plate.

   Note: Prior to mounting the buffer assembly onto the engine, ensure the harness from the sensor to the sensor buffer is not twisted or bound.

3. Slide the tube spacers onto the button head screws.

   Note: If you are installing the 379-0138 Sensor Kit (NITROGEN OXIDE), install the new tube spacers (9), from the kit, onto the bolts.

4. Place the cover onto the bolts.

5. Install washers (10) and nuts (11). Hand tighten the nuts.

Show/hide table



Illustration 3	g02608857
Location of the cover tabs (12) Tabs

6. Loosely install the tie-wraps to tabs (12) on either side of the cover. Tighten the tie-wraps in order to secure the harness firmly to each tab.

7. Tighten cover nuts (11) .

   Torque for the cover nuts ... 25 ± 6 N·m (18 ± 4 lb ft)

Show/hide table



Illustration 4	g02608576
NOX sensor

8. Carefully install NO_X sensor (5) into the exhaust stack.

   Torque for the NO_X sensor ... 50 ± 5 N·m (37 ± 3 lb ft)

9. Connect the engine harness to the buffer connector.

Properly Secure the Sensor Harness

Note: The slack in the harness is crucial to ensuring the service life of the sensor. Ensure that the harness is installed properly and the recommended slack in the harness is according to the following specifications.

Show/hide table



Illustration 5	g02832856
Guide for harness installation (Length A) Slack in the harness between the top harness support and the sensor (Length B) Slack in the harness between the sensor buffer and the bottom harness support

1. Secure the harness to the uppermost clip. Use one of the provided tie-wraps. Ensure that the rachet case of the tie-wraps is positioned on the outside of the clip. Verify that the slack in the harness between the end of the sensor and the point of support matches the recommended slack listed in Table 2.