Oxygen Sensor Heater Before Catalytic Converter, Checking

NOTE:

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

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.

Test sequence

-- Disconnect 6-pin harness connector to the respective oxygen sensor:

Fig 2: Disconnecting 6-Pin Harness Connector To Respective Oxygen Sensor

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Heated Oxygen Sensor (HO2S) -G39-, bank 1, 6-pin harness connector -2-,
Heated Oxygen Sensor (HO2S) 2 -G108-, bank 2, 6-pin harness connector -4-.

NOTE:

Bank 1 = Cylinder bank 1, in direction of travel, right.

Bank 2 = Cylinder bank 2, in direction of travel, left.

Checking voltage supply and wiring to control module

-- Connect multimeter to terminals 3 + 4 of connector to Engine Control Module (ECM) for voltage measurement.

Fig 3: Checking Voltage Between Terminals 3 & 4

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-- Start engine, and let run at idle.

Specified value: at least 7.0 V

If specified value is obtained:

-- Switch ignition off.

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

-- Generate readiness code.

If specified value is not obtained:

-- Connect multimeter to terminal 3 of connector to Engine Control Module (ECM) + Ground (GND) for voltage measurement.

Fig 4: Testing Voltage Between Terminals 3 & Ground

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Specified value: at least 11.0 V

-- Switch ignition off.

If specified value is not obtained:

-- Check voltage supply at 6-pin connector terminal 3 to Motronic Engine Control Module (ECM) Power Supply Relay -J271- according to wiring diagram: Refer to SYSTEM WIRING DIAGRAM

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

-- Generate readiness code.

If specified value is obtained:

-- Check Ground (GND) activation of the respective oxygen sensor heater.

Checking Ground (GND) activation of oxygen sensor heating

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

-- Check wires between test box and 6-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.

Fig 5: 6-Pin Harness Connector & Terminals

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

Wire resistance: max. 1.5Ω

Component	Connector	Test box
Bank 1 sensor 1	Terminal 4	Socket 5
Bank 2 sensor 1	Terminal 4	Socket 4

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

Specified value: ∞ Ω

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

-- Generate readiness code.

If no malfunctions are found in wires:

-- Replace Motronic Engine Control Module (ECM) -J220- ENGINE CONTROL MODULE, REPLACING .