O2 Sensor FYI
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TReK
Joined: Sep 2010
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From: Ketchikan, Alaska, USA
HEATED OXYGEN SENSORS
The Heated Oxygen Sensor (H02S ) mounted in the exhaust downpipe serves as the key input in an electronic fuel injection system. The sensor is used by the ECM to determine the amount of oxygen present m the exhaust gas. The ECM uses this information to increase or decrease injector open time to bring the air/fuel ratio as close to Stoichiometric as possible.
Additional oxygen sensors are mounted in the exhaust system, downstream from each of the vehicle's catalytic converters. Data from these new sensors is compared with the signal produced by the front sensor on each bank. This information is used by the GEMS to monitor performance of the Three-Way Catalyst (TWC ).
The rear sensors are also part of the ECM's fuel system back-up strategy. Should the signal from the front HO2S fail, the signal from the corresponding rear sensor will be used so that the vehicle can remain in closed-loop operation.
All Land Rover systems use sensors that change resistance in the presence of oxygen in the exhaust. The ECM is able to calculate the amount of oxygen in the exhaust based on this change.
Both types of oxygen sensor signals are continually "switching" as the ECM changes injector pulse width in response to the sensor messages. On systems with more than one sensor, the ECM monitors each sensor separately. Fuel trim adjustments are made independently to each cylinder bank, or individual cylinder, depending on the fuel system.
Oxygen sensors operate efficiently only when warm. Sensors include heaters to help them reach operating temperatures quickly. This allows the sensors to provide accurate information to the ECM soon after start-up and the system to enter closed loop operation (based on sensor inputs) sooner. Closed loop operation helps provide an efficient fuel mixture and controls emissions when the engine is cold. Closed loop also guards against catalytic converter overheating from the introduction of too much fuel.
In their operating environment, oxygen sensors are quite durable. However, they are easily damaged if dropped, exposed to excessive heat, or contaminated. Care should be taken when handling oxygen sensors.
Be careful when replacing an oxygen sensor. Contamination of the sensor body can lead to premature failure. The sensor threads must be sealed with the material provided to ensure there are no oxygen leaks. Do not use silicone sealants for this purpose as they will contaminate the sensor.
The Heated Oxygen Sensor (H02S ) mounted in the exhaust downpipe serves as the key input in an electronic fuel injection system. The sensor is used by the ECM to determine the amount of oxygen present m the exhaust gas. The ECM uses this information to increase or decrease injector open time to bring the air/fuel ratio as close to Stoichiometric as possible.
Additional oxygen sensors are mounted in the exhaust system, downstream from each of the vehicle's catalytic converters. Data from these new sensors is compared with the signal produced by the front sensor on each bank. This information is used by the GEMS to monitor performance of the Three-Way Catalyst (TWC ).
The rear sensors are also part of the ECM's fuel system back-up strategy. Should the signal from the front HO2S fail, the signal from the corresponding rear sensor will be used so that the vehicle can remain in closed-loop operation.
All Land Rover systems use sensors that change resistance in the presence of oxygen in the exhaust. The ECM is able to calculate the amount of oxygen in the exhaust based on this change.
Both types of oxygen sensor signals are continually "switching" as the ECM changes injector pulse width in response to the sensor messages. On systems with more than one sensor, the ECM monitors each sensor separately. Fuel trim adjustments are made independently to each cylinder bank, or individual cylinder, depending on the fuel system.
Oxygen sensors operate efficiently only when warm. Sensors include heaters to help them reach operating temperatures quickly. This allows the sensors to provide accurate information to the ECM soon after start-up and the system to enter closed loop operation (based on sensor inputs) sooner. Closed loop operation helps provide an efficient fuel mixture and controls emissions when the engine is cold. Closed loop also guards against catalytic converter overheating from the introduction of too much fuel.
In their operating environment, oxygen sensors are quite durable. However, they are easily damaged if dropped, exposed to excessive heat, or contaminated. Care should be taken when handling oxygen sensors.
Be careful when replacing an oxygen sensor. Contamination of the sensor body can lead to premature failure. The sensor threads must be sealed with the material provided to ensure there are no oxygen leaks. Do not use silicone sealants for this purpose as they will contaminate the sensor.
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