NOx Sensor Installation and Handling Procedures for Certain G3500H Series Engines {1335, 1408, 191N} Caterpillar

Engine

G3512H (S/N: GF51-119)

G3516H (S/N: NWH1-138; NWJ1-108; GLM1-188; GLN1-138)

G3520H (S/N: GFP1-181; GFR1-195)

Generator Set

CG170-16 (S/N: KSJ1-167)

Introduction

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

Failure to route or handle NOx sensors properly can result in premature failure of the sensor or wiring.

Important Safety Instructions

Do not perform any procedure in this Special Instruction until you have read this Special Instruction and you understand this information. Use only proper tools and observe all precautions that pertain to the use of those tools. Failure to follow these procedures can result in personal injury. The following procedures should be observed.

Work safely. Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs.

A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools to perform these functions properly. Safety precautions and warnings are provided in this instruction and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. Therefore, the warnings in this publication and the warnings that are on the product are not all inclusive.

Ensure that any tool, procedure, work method, or operating technique you use that is not recommended by Caterpillar is safe. Ensure that the product will not be damaged or the product will not be made unsafe by the operation, lubrication, maintenance, or repair procedures used.

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Do not operate or work on this product unless you have read and understood the instruction and warnings in the relevant Operation and Maintenance Manuals and relevant service literature. Failure to follow the instructions or heed the warnings could result in injury or death. Proper care is your responsibility.

Required Parts

General Handling Procedures

Use the following list below as general handling guidelines for the NOx sensor and wiring harness.

• Do not unplug the NOx sensor cable when the sensor is powered on, damage to the engine ECM may occur.

• Avoid impacting the NOx sensor, dropping the sensor could cause permanent damage. If the sensor is impacted, discard the sensor.

• Handle and store the NOx sensor in a clean, dry area that is free of contamination and inclement weather.

• The sensing unit protective cap should not be removed until the sensor is ready for installation.

• Do not paint any part of the sensing unit.

• Allow the exhaust system to cool before removing the sensor.

• Avoid temperature shock when opening a shipping box. Avoid a temperature difference of 5° ± 5°C (41° ± 41°F) between sensors and the environment. Allow at least 4 hours for the sensors to reach ambient temperature before opening the box to avoid condensation on the parts.

• Do not open the shipping box with a knife that can deeply penetrate the box. Knives can damage the sensor or sensor cables.

NOx Sensor Installation Procedures

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Illustration 1	g03695896
(1) Electrical Connector (2) Cable (varnish tube sleeve) (3) Grommet (4) Hex Nut (5) Threads (6) Protective Cover (7) Mounting Tabs

1. Mount the ECU with hardware.

2. Install the ECU sensor harness clamp.

   Note: Do not bend the cable sharply. Route the sensor cable and secure the cable as the original cable was installed.

3. Remove the protective cap from the sensing unit. Do not lubricate the threads of the new sensor. The threads come pre-lubricated from the factory.

   Note: Non-metallic anti-seize is the only approved thread lubricant to be used when reinstalling a sensor.

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   Illustration 2	g06266056

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   Illustration 3	g06266057

4. Place the sensing unit in the mounting boss on the exhaust outlet elbow and turn the hex nut by hand until tight.

   Note: Hold the base of the sensing unit neat the grommet so the cable does not twist while turning the hex nut. The maximum allowable cable rotation after tightening is 180 degrees.

5. Tighten the hex nut to 50 ± 10 N·m (37 ± 7 lb ft).

6. Carefully place sensor harness inside the p-clips, ensuring not to pull on the harness or to put tension on the harness.

7. Connect the sensor wiring harness to the sensor buffer module and install the cable strap.

Illustration 4	g06209618
This is NOT a proper installation of a NOx sensor.

When NOx sensor installation is complete, inspect the exhaust insulation at the exhaust outlet and the flex coupling insulation. There must be adequate air flow around the NOx sensor probe to prevent overheating. Refer to Illustration 4.

Sensor probe grommet has a maximum temperature of 200° C (392° F).