Series 50G/60G Troubleshooting – Section 3.7 Oxygen Sensor

Section 3.7
Oxygen Sensor

The oxygen sensor measures exhaust oxygen which is an indication of the air/fuel ratio (see Figure "Oxygen Sensor" ). The air/fuel ratio is a fundamental parameter for a natural gas engine. Precise control of the air/fuel ratio allows the engine to operate closer to the lean limit. As a result, exhaust emissions, fuel consumption, and exhaust temperatures are reduced.‪

Figure 1. Oxygen Sensor

If fuel system hardware, fuel quality, or engine operating conditions change, DDEC will sense this and make corrections to keep the air/fuel ratio on target. This is called “closed loop” control.‪

The oxygen sensor must be installed in the exhaust pipe within 305 mm (12 in.) of the turbine outlet. The sensor has pre-applied anti-seize on the threads. The oxygen sensor harness must be used to connect the sensor to the oxygen sensor interface module located at the rear of the engine. The wires must be routed away from the exhaust system and kept out of contact with moving parts.‪

Check the Oxygen Sensor for proper operation as follows:‪

1. Place the diagnostic oxygen sensor (Engine Control & Monitoring Inc. diagnostic oxygen sensor, Lambda PRO™ kit or equivalent, in the secondary port in the exhaust tube.

   ‪

   Lambda Pro trademark is owned by ECM Engine Control and Monitoring.‪

2. Connect the DDR or DDDL and display air/fuel ratio Lambda value.

   NOTICE:
   Use care not to overheat the transmission during the stall torque test. Overheating the transmission will cause damage.‪

3. Perform a transmission stall torque test.
   1. Run the stall for approximately 10 seconds.

      Note: Engine and transmission should be at normal operating temperatures.

   2. Record the air/fuel ratio Lambda value displayed by DDEC and the diagnostic oxygen sensor.
4. Waiting one minute between tests, repeat step twice.
   1. If the readings between the diagnostic oxygen sensor and DDEC oxygen sensor are more than +/- 0.02 Lambda different, replace the Oxygen Sensor (see Figure "Oxygen Sensor" ) and then perform the Learn Procedure. Refer to "3.8 Fuel System Learn Procedure" .
   2. If the readings between the diagnostic oxygen sensor and DDEC oxygen sensor are less than or equal to +/- 0.02 Lambda, replace the Low Pressure Regulator, refer to "3.6.3 Replacing the Throttle" .
5. If the engine operates normally, troubleshooting is done.