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Heated Oxygen Sensors Diagnostic
Heated Oxygen Sensors Diagnostic
An S80 car with EMS system that meets ULEV2/EURO4 legal demands is fitted with two heated oxygen sensors per bank. The upper sensor is fitted before the CCC and the second sensor after the CCC and before the UFC (under floor catalyst). The upper sensor is linear type and the second is a binary type.
The upper sensors have the following monitoring:
- Slow activation (P-code P0134 and P0154). When the Oxygen sensor heater circuit start to heat up the element, a delay counter is activated. After a specified time of heating is a judgment done by evaluating sensor element impedance. Continues monitoring.
- Slow response (P-code P0133 and P0153). A dither is added to target lambda. The diagnose will then check if the lambda value can follow this square wave. When the sensor is slow enough to give high emission it will be detected as malfunctioning. Performed once per driving cycle.
- Heater circuit (P-code P0031, P0032 and P0051, P0052). The sensor heater is continuously monitored. Fault will be detected if circuit is: Open, short to ground or short to battery.
- Sensor circuit (P-code P0131, P0132 and P0151 and P0152). The sensor circuit is continuously monitored. Fault will be detected if sensor circuit is: Open, short to ground or short to battery.
The second sensors have the following monitoring:
- Sensor circuit (P-code P0137, P0138 and P0157, P0158). The sensor working range is checked to detect if sensor have an amplitude/range problem to work in its normal voltage range. Sensor must be able to work in catalyst monitoring area to be judged as normal and be close to 0 V after fuel cut. Function also monitor if sensor is stuck in range.
- Heater circuit (P-code P0037, P0038 and P0057, P0058). The sensor heater is continuously monitored. Fault will be detected if circuit is: Open, short to ground or short to battery.
- Sensor out of range (P-code P1137, P1138 and P1157, P1158). If sensor doesn't work in its normal range, fault will be detected. Continuous monitoring.
