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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 ].