Lotus 2004 Eleven Service Notes page 161

Lotus Service Notes
O2 Sensor (Post Catalyst)
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
1
2
3
4
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
Page 18
P0137
P0138
P0139
P0140
P0141
Description ECU Pin
Signal 3 (B3)
Ground 29 (F4)
Heater 27 (H3)
Battery Voltage -
ECU Connector
52 Way (Left)
52 Way (Left)
52 Way (Left)
-
Section EMP
'06 M.Y. in brackets