Oxygen Sensors And Sensor Regulation After Catalytic Converter, Checking

Special tools and workshop equipment required 

• Multimeter VAG1526 or multimeter VAG1715
• Connector test kit VAG1594
• Wiring diagram

Test requirements 

• Fuses in E-box (in plenum chamber, left) must be OK: Refer to SYSTEM WIRING DIAGRAM
  Fig 1: Identifying Fuses In E-Box (In Plenum Chamber, Left)

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Motronic Engine Control Module (ECM) Power Supply Relay -J271- must be OK, check: Refer to SYSTEM WIRING DIAGRAM
• Battery voltage must be at least 11.5 volts.
• All electrical consumers such as, for example, lights and rear window defroster must be switched off.
• Parking brake must be engaged or else daylight driving lights will be switched on.
• For vehicles with automatic transmission, selector lever must be in P position.
• 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.
• Coolant temperature must be at least 80° C, Diagnostic mode 1: Check measured values; PID 5, Coolant temperature.
• Oxygen sensor heater for oxygen sensors behind catalytic converter must be OK, check OXYGEN SENSOR HEATER AFTER CATALYTIC CONVERTER, CHECKING .

Function test 

-- Select the output of oxygen sensor signals and check whether the specified values are being reached, Diagnostic mode 5: Check output of oxygen sensor signals.

-- End diagnosis and switch ignition off.

If specified values are not obtained:

-- Check oxygen sensor wires according to wiring diagram.

Checking oxygen sensor wires 

-- Connect test box to control module wiring harness, connect test box for wiring test.

-- Disconnect 4-pin harness connector to the respective oxygen sensor:

• Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130-, bank 1, 4-pin harness connector 1-,
• Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131-, bank 2, 4-pin harness connector 3-,

-- Check wires between test box and 4-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.

Wire resistance: max. 1.5 Ω

Component	Connector	Test box
Bank 1 sensor 2	Terminal 3	Socket 68
	Terminal 4	Socket 69
Bank 2 sensor 2	Terminal 3	Socket 10
	Terminal 4	Socket 11

-- Also check wires for short circuit to B+ or Ground (GND).

Specified value: ∞ Ω

If no malfunctions are found in wires:

-- Replace the respective oxygen sensor:

• Bank 1 Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130-,
• Bank 2 Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131-.

-- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.

-- Generate readiness code.