Oxygen Sensor Before Catalytic Converter, Checking Function

Oxygen Sensor before Catalytic Converter, Checking Function

• When servicing terminals in harness connector of oxygen sensor, use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter (VAG1526) or Multimeter (VAG1715)

• Connector test kit (VAG1594)

• Wiring diagram

Test Prerequisites

• The respective fuses of Heated Oxygen Sensor (HO2S) (G39) and Heated Oxygen Sensor (HO2S) 2 (G108) must be OK:

• Battery voltage must be at least 11.5 volts.

• Oxygen sensor heaters for oxygen sensors before catalytic converter must be OK (no DTC entry).

• All electrical consumers such as, lights and rear window defroster must be switched off.

• Parking brake must be engaged or else daylight driving lights will be switched on.

• If vehicle is equipped with an A/C system, it must be switched off.

• Ground (GND) connections between engine and chassis must be OK.

• Exhaust system must be properly sealed between catalytic converter and cylinder head.

Function Test

- Coolant temperature must be at least 80°C => [ Diagnostic Mode 01 - Read Current System Data ] Diagnostic Modes 01 - 09, Diagnostic mode 1: Check measured values; PID 5, Coolant temperature.

- Select the following output of oxygen sensor signals and check whether the specified values are being reached => [ Diagnostic Mode 05 - Read Oxygen Sensor Monitoring Test Results ] Diagnostic Modes 01 - 09, Diagnostic mode 5: Check output of oxygen sensor signals.

- Check specified values of the output of oxygen sensor signals at idle:





*) V = Voltage in Volts (oxygen sensor signal)

**) t = Time in seconds





• Cylinder bank 1 = in driving direction, right

• Cylinder bank 2 = in driving direction, left

If specified values are obtained:

- End diagnosis and switch ignition off.

If specified values are not obtained:

- End diagnosis and switch ignition off.

- Check signal wire and activation of oxygen sensor before catalytic converter => [ Oxygen Sensors before Catalytic Converter, Checking Signal Wire and
Activation ].