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Lotus Service Notes
Section EMP O2 Sensor (Post Catalyst) P0137 P0138 P0139 P0140 P0141 P0137 O2 Sensor Circuit Low Voltage P0138 O2 Sensor Circuit High Voltage P0139 O2 Sensor Circuit Slow Response P0140 O2 Sensor Circuit No Activity Detected P0141 O2 Sensor Heater Circuit Description The oxygen sensor monitors the oxygen content in the exhaust gases. The sensor consists of a zirconia elec- trode between two platinum plates. When zirconia comes into contact with oxygen, it becomes an electrical conductor. The exhaust gases passes through louvers in the sensor. One plate is in contact with the outside air and the other plate is in contact with the exhaust gases. The platinum plate in contact with the air is electrically negative due to the oxygen in the atmosphere and the plate in contact with the exhaust gases is electrically positive. This will cause a difference in electrical potential to develop between the two plates. Thus the voltage across the platinum plates ranges approximately from 100 millivolts to 900 millivolts, depending on the oxygen content of the exhaust gases. Thus when the air/fuel mixture is rich, the oxygen sensor output will be high. If the air/fuel mixture is lean, the oxygen sensor output will be low. The post catalyst oxygen sensor performance is a good indicator of catalyst efficiency. Sensor connections Sensor Connector Description ECU Pin ECU Connector 1 Signal 3 (B3) 52 Way (Left) 2 Ground 29 (F4) 52 Way (Left) '06 M.Y. in brackets 3 Heater 27 (H3) 52 Way (Left) 4 Battery Voltage - - Sensor characteristics Normal operating range is 0 – 1000mV Malfunction Criteria P0137 Set when the sensor operates below 5mV for more than 1.5 seconds consecutively for a specified number of times. Monitor: Continuous Disable Criteria: DFCO (Deceleration Fuel Cut Off) Potential failure modes: • Check and rectify any pre catalyst sensor fault code, as they may be causing the fault code to be set • Sensor wire shorted to ground • Catalyst P0138 Set when the sensor operates above 1200mV for more than 1.5 seconds consecutively for a specified number of times. Monitor: Continuous sn_emp_cyclone.indd 18 03/03/2006 11:03:36 |