KIT-TEST 2985311 - Caterpillar

Narrow Band O2 Sensors
System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the oxygen sensors. Also, use this procedure if one of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table
J1939 Code and Description Conditions which Generate this Code System Response
3217-3 Aftertreatment Intake %O2 : Voltage Above Normal The Electronic Control Module (ECM) may have detected a short circuit to the +Battery. The ECM may have detected an open circuit in the signal circuit for the oxygen sensor at the turbocharger exhaust outlet. The code is logged.
The amber warning lamp is illuminated.
The ECM uses the last good value from the oxygen sensor for the control of exhaust emissions.
3227-3 Aftertreatment Outlet %O2 : Voltage Above Normal The ECM may have detected a short circuit to the +Battery. The ECM may have detected an open circuit in the signal circuit for the oxygen sensor at the outlet of the catalytic converter.
Illustration 1 g02036913
Oxygen sensor and buffer
(1) Oxygen sensor
(2) Sensor bufferThe oxygen sensors are used to monitor the emission level of the engine exhaust. The ECM utilizes the signal from the oxygen sensors to adjust the air/fuel ratio. This strategy ensures that the engine burns the fuel efficiently. Two oxygen sensors are used for this application. One of the oxygen sensors is mounted in the turbocharger exhaust outlet. The other oxygen sensor is mounted in the output flange of the catalytic converter. Each sensor circuit consists of an oxygen sensor and a sensor buffer. A voltage converter is used to power both sensor circuits.The oxygen sensors are used to detect the level of oxygen in the engine exhaust. The sensors generate voltage signals that are directly proportional to the concentration of oxygen. The usable range of each signal is 150 mV to 750 mV. A lean concentration level will produce a 150 mV signal and a rich concentration level will produce a 750 mV signal. This analog signal is sent to the sensor buffer. Each oxygen sensor utilizes a heating element to heat the sensing element of the sensor. The use of the heating element improves the warmup time and the accuracy of the sensor.Note: The sensors have an operating range of 600° C to 800° C (1100° F to 1500° F). The tip of the sensors may be hot. Use caution when you handle the oxygen sensors.The sensor buffer is used to filter the electronic signal that is sent from the oxygen sensor. The buffer acts as a filter to condition the analog signal before the signal is sent to the ECM.The voltage converter converts a filtered 24 VDC from the ECM to 12 VDC that is used by the sensor circuit. The voltage converter provides 12 VDC to each of the buffers. Each buffer supplies 12 VDC to the oxygen sensor. Each sensor supply is used to power the heating element and the supply circuit for the analog sensor.A -3 diagnostic code indicates that a problem has been