WIS 07.61 Gasoline Engine and Injection System ME

Back to Index

Heated Oxygen Sensors (HO2S) - Gasoline Engine and Injection System

Description - Heated Oxygen Sensors (HO2S)

The Heated Oxygen Sensors (HO2S) are commonly known as O2 Sensors or Lambda Sensors. They are used to monitor, in real time, whether the air–fuel ratio of a combustion engine is rich or lean. Note: the Upstream 02 Sensors have a dramatic effect on performance and fuel economy but the down stream sensors are only used to monitor the performance of the catalytic converters and emissions.

They work by producing a voltage from approximately 1.0 V during rich operating conditions to 0.01 V (10 mV) during lean operating conditions. The HO2S is like an open circuit and produces no voltage when it is below 360C (600F).

The powertrain control module (PCM) supplies a bias voltage of about 450 mV between the heated oxygen sensor (HO2S) high signal and low signal circuits. The HO2S varies the voltage within a range of about 1,000 mV when the exhaust is rich, down through about 10 mV when exhaust is lean. The PCM constantly monitors the HO2S signal during Closed Loop operation and compensates for a rich or lean condition by decreasing or increasing the fuel injector pulse width as necessary. If the HO2S voltage remains at or near the 450 mV bias for an extended period of time, P0154 diagnostic trouble code (DTC) will be set.

http://en.wikipedia.org/wiki/Oxygen_sensor

Location - Heated Oxygen Sensors (HO2S)

• G3/3 Left and G3/4 Right are the Heated Oxygen Sensors before or upstream of the Catalytic Converter TWC (KAT).
• G3/5 Left and G3/6 Right are the Heated Oxygen Sensors after or downstream of the Catalytic Converter TWC (KAT).

Issues - Heated Oxygen Sensors (HO2S)

HO2S have a limited lifetime, typically 160,000 Km (100,000 miles).

Symptoms of a failing HO2S include:

• Warning light on dash,
• Increased tailpipe emissions,
• Increased fuel consumption,
• Hesitation on acceleration,
• Stalling,
• Rough idling.

Heating Element Failure

The HO2S contains a heating element which often fails by going open circuit. The resistance of a typical W220 heater element has been measured as 9.2 Ohms. The specified heater resistance is TBD.

Resulting Fault Codes are:

• P20BF-004 G3/3 Left HO2S before TWC (KAT) open circuit in sensor heater line (P0156)
• P2082-004 G3/3 Left HO2S before TWC (KAT) open circuit (P0154)

Cable Lengths

The W220 HO2S are electrically interchangeable but have different cable lengths.

• G3/3 Left and G3/4 Right Front or Upstream HO2S (Long Cable). Wire length: 440mm (17.3 inches) sensor washer to end of connector. Total length: 460mm.
• G3/5 Left and G3/6 Right Rear or Downstream HO2S (Short Cable). Wire length: 322mm (12.7 inches) sensor washer to end of connector. Total length: 340mm.

Part Numbers - M113 V8's

• Left and Right, Front or Upstream HO2S (Long Cable): Bosch 16274
• Left and Right, Rear or Downstream HO2S (Short Cable): Bosch 16276

Contamination

Contamination of the oxygen sensor can result from the use of an inappropriate RTV or silicon sealer (not oxygen sensor safe) or excessive engine coolant or oil consumption.

• To check remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination.
• If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating.
• Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe drive-ability problem.
• Eliminate the source of contamination before replacing the oxygen sensor.

Connector Pin Diagram - Heated Oxygen Sensors (HO2S)

HO2S Wire Colours

• Pin 1 White Heater
• Pin 2 White Heater
• Pin 3 Grey O2 Sensor Low
• Pin 4 Black O2 Sensor High

HO2S Connector to Power Control Module (N3/10) Cable Wire Colours

• Pin 1 Red or Red/Green Heater Ground
• Pin 2 Brown or Brown/Black Heater +12V
• Pin 3 Green O2 Sensor Low
• Pin 4 Black O2 Sensor High

Electrical Wiring Diagram HO2S Upstream of TWC [KAT]

DIY Video - Heated Oxygen Sensors (HO2S)

Load video YouTube YouTube might collect personal data. Privacy Policy ContinueDismiss Bank 1 or Bank2 O2 Sensor 2 DIY - M113, M112 Engines (By Masood)

The following codes may require replacement of the O2 sensor 2:

Engine codes for Bank1 Sensor 2:

• P2031 Exhaust Gas Temperature Sensor Circuit (Bank 1 Sensor 2)
• P2032 Exhaust Gas Temperature Sensor Circuit Low (Bank 1 Sensor 2)
• P2033 Exhaust Gas Temperature Sensor Circuit High (Bank 1 Sensor 2)
• P0136 O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
• P0137 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
• P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
• P0139 O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
• P0140 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
• P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

Engine codes for Bank2 Sensor 2 are:

• P0156 O2 Sensor Circuit Malfunction (Bank 2 Sensor 2)
• P0157 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
• P0158 O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)
• P0159 O2 Sensor Circuit Slow Response (Bank 2 Sensor 2)
• P0160 O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)
• P0161 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2):

DIY Articles - Heated Oxygen Sensors (HO2S)

http://www.benzworld.org/forums/w203-c-class/1474361-p0154-code-wont-go-away.html

http://www.benzworld.org/forums/w203-c-class/1474361-p0154-code-wont-go-away-2.html

http://www.hotrodlane.cc/New%20LS%20Links%20Page/LS%20trouble%20codes/DTC%20P0154.htm

Fuel Injectors - Gasoline Engine and Injection System

Description - Fuel Injectors

Edit required.