G3500H Generator Set Engine Caterpillar

Nitrogen Oxide Level - Test

Usage:

Use this procedure to troubleshoot a problem with the NOx sensor group. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.

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Table 1
J1939 Code and Description	Comments
3216-2 Aftertreatment #1 Intake NOx : Erratic, Intermittent, or Incorrect	The NOx sensor has detected a problem with the stability of the detected NOx level. The code is active after 3 minutes of continued instability of exhaust NOx levels. The code is inactive after detected NOx levels return to normal levels for 60 seconds.
3216-4 Aftertreatment #1 Intake NOx : Voltage Below Normal	The NOx sensor has detected that the power supply is not in range.
3216-6 Aftertreatment #1 Intake NOx : Current Above Normal	The Electronic Control Module (ECM) detects a short in the power supply circuit for the NOx sensor. The code is logged.
3216-12 Aftertreatment #1 Intake NOx : Failure	During a self-test, the NOx sensor has detected an internal fault. Replace the sensor The code is logged.
3216-14 Aftertreatment #1 Intake NOx : Special Instruction	During a self-test, the NOx sensor has detected an internal fault. Replace the sensor The code is logged.
5758-6 Aftertreatment #1 Intake Gas Sensor Power Supply : Current Above Normal	The ECM detects a short in the power supply circuit for the NOx sensor. The code is logged.
5758-11 Aftertreatment #1 Intake Gas Sensor Power Supply : Other Failure Mode	The NOx sensor has detected that the power supply is not in range.

The NOx sensor group is used by the ECM to measure the level of NOx concentration in the engine exhaust. This value is reported back to the ECM via the CAN data Link. The ECM uses this information to control the air/fuel ratio for the engine. By controlling the air/fuel ratio, the ECM is able to control the engine operation for optimum performance at reduced exhaust emissions.

The NOx sensor group is made up of two integrated components:

Sensor - The NOx sensor consists of a ceramic element that measures the concentration of NOx in the exhaust gas. The sensor contains a heating element that is used to heat the sensor to approximately 800 °C (1450 °F). Once the heating element reaches this temperature, the sensor begins sending NOx data to the sensor buffer.

Sensor buffer - The sensor buffer is used to process the signals that are received from the sensor. The buffer transmits this information to the ECM via the CAN data link. The buffer also reports diagnostic data to the ECM over the CAN data link. The sensor buffer is powered by a (100 % ON) Pulse Width Modulated output (PWM output). The ECM is the power source. The sensor buffer requires 18 V to 36 V to operate.

The sensor and the sensor buffer are integrated parts. The sensor and the sensor buffer must be replaced as a single component, if necessary.

NOx Sensor Power Supply Enablement Conditions

A Cat ET service test, for overriding the power supply may be available for diagnostic testing purposes. If an override is unavailable, starting, and running the engine in accordance with the sensor buffer power-on requirements will be necessary.

The buffer is powered by the ECM after the following conditions are verified:

No diagnostic codes related to the NOx sensor are active
Engine speed above 500 rpm
Engine accumulated run time duration up to 3 minutes to remove moisture from sensor.
The calculated power on delay time has expired.

An active diagnostic code is probably caused by a problem with a connector or harness for the CAN data link or the power supply. The next likely cause is a problem with the NOx sensor group. The least likely cause is a problem with the ECM.

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Illustration 1	g06137686
For the complete circuit details, refer to the full schematic.

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Illustration 2	g03695896
NOx sensor assembly (1) Electrical connector (2) Cable (with varnish tube sleeve) (3) Grommet (4) Hex nut (5) Threads (6) Protective cover (7) Mounting tabs (8) NOx sensor buffer

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Table 2
Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Thoroughly inspect the connectors. Refer to Troubleshooting, "Electrical Connectors-Inspect" for additional information. C. Perform a 45 N (10 lb) pull test on the connector wires. D. Check the harness for abrasions and pinch points.	Connectors and Wiring	Result: The connectors and wiring appear to be OK. Proceed to Test Step 2. Result: There is a problem with the connectors and/or wiring. Repair: Repair or replace the connectors or wiring. Ensure that all the seals are properly in place and ensure that the connectors are coupled. If problem is not resolved, proceed to Test Step 2.
2. Check for Codes A. Connect Cat^® Electronic Technician (ET) to the service tool connector. B. Determine if a code is active or logged.	Codes	Note: If a CAN Data Link -9 code is active or logged against the NOx sensor, troubleshoot the -9 code before performing this procedure. Result: There is a code with FMI -2. Proceed to Test Step 3. Result: There is a code with FMI -6. Proceed to Test Step 4. Result: There is a code with FMI -11 or an FMI -12. Repair: Replace the NOx sensor group. Verify that the repair eliminated the problem.
3. Inspect the NOx Level Sensor Condition and Installation A. Ensure proper sensor torque mounting 50 ± 10 N·m (37 ± 7 lb ft). B. Ensure that temperature of the sensor grommet does not exceed 200° C (392° F). Note: Temperatures that exceed this value will cause early sensor failure. C. Ensure that the sensor is not covered by insulation or heat wrap. D. Ensure that temperature of electronic NOx sensor buffer does not exceed 85° C (185° F). E. Check Cat ET for individual NOx values if available and stable. F. Ensure that the engine control is in OFF/RESET position. G. Remove sensor from the exhaust bank. H. Inspect the sensor for deposits that may be covering the holes in the element. Clean the body sensing element. I. Install the sensor back in the exhaust stack. J. Start the engine. K. Run the engine until normal operating temperature is reached. L. Use Cat ET to monitor the following codes: - -2 code	Codes	Result: A -2 code is not active. Return to service. If the code continues to return to an active status, refer to the Application and Installation Guide for more information on proper NOx sensor installation and servicing. Result: The -2 code remains active, replace the NOx sensor group. Verify that the repair eliminated the problem.
4. Check the Wiring Harness for a Short Circuit to Ground A. Turn the main disconnect switch to the ON position. B. If available, activate the Cat ET service override for the NOx sensor power supply. If unavailable, start the engine and run in accordance with NOx sensor power supply enablement conditions listed in the beginning of this procedure. C. Connect Cat ET. D. Use Cat ET to monitor the following codes: - -6 code	Codes	Result: A -6 code for a NOx sensor is active or logged. A short circuit in the wiring harness between the Electronic Control Module (ECM) and the NOx sensor power supply has been detected. Repair: Repair or replace the wiring harness. Verify that the repair eliminated the problem.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).