Causes of a 3002-2 Diagnostic Code for Some G3512 and G3516 Engines{1408, 1900, 191N, 7400} Caterpillar

Engine:

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

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

Introduction

The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.

Problem

The NO_X sensor informs the ECM that the data from the sensor is incorrect.

Solution

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Illustration 1	g01400239
(1) Tie-wraps (2) Support brackets

1. Check the routing of the sensor, buffer, and harness. Refer to Illustration 1. If the routing of the sensor, buffer, and harness is incorrect, refer to Special Instruction, REHS3411, "Installation of the 304-4209 Nitrogen Oxide Sensor Gp" for the correct routing and then proceed to Step 2.

2. Check the stability of the engine:

   1. Start the engine. Allow the engine to warm to operating temperature.

   2. Use Caterpillar Electronic Technician (ET) to monitor the engine rpm for a two minute period. Check that the engine rpm remains stable within ±10 rpm from the desired engine speed.

      Note: An unstable engine rpm can cause the NO_X concentrations in the exhaust to become unstable. A 3002-2 diagnostic code may become active because of this. Troubleshoot the engine for the unstable engine rpm before you continue with this procedure.

   3. Use Cat ET to check the value of the intake manifold pressure. The 3002-2 diagnostic code may become active if the engine's intake manifold pressure is less then 90 kPa (13 psi). Troubleshoot the engine for a low intake manifold pressure before you continue with this procedure.

3. Ensure that the engine control is in the OFF/RESET position. Allow the engine to cool.

4. Use a paint stick to mark the orientation of the NO_X sensor in the exhaust stack.

5. Remove the sensor from the exhaust stack.

6. Inspect the sensor for deposits that may be covering the holes that are in the body of the sensing element. If necessary, clean the body of the sensing element with compressed air.

7. Install the sensor into the exhaust stack. During the installation, use the markings that are from the paint stick to orient the sensor. Orient the sensor at approximately 90 degrees from the previous orientation in the exhaust stack.

   Torque ... 50 ± 10 N·m (37 ± 7 lb ft)

8. Start the engine. Allow the engine to warm to operating temperature.

9. Use Cat ET to monitor active diagnostic codes for the NO_X sensor.

10. If the original diagnostic code is no longer active, the problem has been resolved. Return the engine to service.

11. If the 3002-2 diagnostic code remains active or intermittent, please work through your dealer Technical Communicator to contact the DSN (Dealer Solution Network) for information necessary to complete any repairs.