Oxygen Sensor Heater, Checking

NOTE:

Cylinder bank 1 is located in direction of travel, right.

Cylinder bank 2 is located in direction of travel, left.

Use only gold-plated terminals when servicing terminals in harness connector.

Special tools and workshop equipment required

Multimeter VAG1526 or Multimeter VAG1715
Connector test kit VAG1594
Wiring diagram

Test Prerequisites

Fuses in E-box (plenum chamber, left) must be OK: Refer to SYSTEM WIRING DIAGRAM

Fig 1: Identifying Fuse Holder
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Power Supply Relay (Terminal 30, B+) Relay 2 -J689-, 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.
For vehicles with automatic transmission, selector lever must be in P.
If vehicle is equipped with an A/C system, it must be switched off.
Ground (GND) connections between engine and chassis must be OK.
Coolant temperature must be at least 80 °C DIAGNOSTIC MODE 01 - READ CURRENT SYSTEM DATA .
Ignition is switched off.

-- Disconnect 6-pin harness connector -B- to Heated Oxygen Sensor (HO2S) -G39-.

Fig 2: Identifying 6-Pin Harness Connector -B- To Heated Oxygen Sensor (Ho2S) -G39-

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Sensor Heater, Checking Resistance

-- Check resistance for sensor heater at connector to oxygen sensor terminal 3 +4.

Fig 3: Checking Resistance For Sensor Heater At Connector To Oxygen Sensor Terminals 3 + 4

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Specified value: Max. 10 Ω (at room temperature)

If specified value is not obtained:

-- Replace Heated Oxygen Sensor (HO2S) -G39-.

-- Erase DTC memory of Engine Control Module (ECM) DIAGNOSTIC MODE 04 - ERASE DTC MEMORY

-- Generate readiness code READINESS CODE .

If specified value is obtained:

-- Check voltage supply and wiring to control module.

Checking Voltage Supply and Wiring

-- 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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-- Start engine, and let run at idle.

Specified value: at least 9.0 V

-- Switch ignition off.

If specified value is not obtained:

-- Check wire from 6-pin connector terminal 3 to Power Supply Relay (Terminal 30, B+) Relay 2 -J689- according to wiring diagram: Refer to SYSTEM WIRING DIAGRAM

-- Erase DTC memory of Engine Control Module (ECM) DIAGNOSTIC MODE 04 - ERASE DTC MEMORY

-- Generate readiness code READINESS CODE .

If specified value is obtained:

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

Checking Ground Activation

-- Connect test box (VAG1598/42) to Engine Control Module (ECM) -J623- wiring harness using adapter cable (VAG1598/39-2), connecting 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: Identifying 6-Pin Harness Connector & Terminals

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Terminal 4 + socket 51

Wire resistance: max. 1.5Ω

-- Also check the wire for short circuit to B+ and Ground (GND).

Specified value: ∞ Ω

If no malfunctions are found in wires:

-- Replace Engine Control Module (ECM) -J623- ENGINE CONTROL MODULES, REPLACING .

Oxygen Sensor Heater 2 (Z28) Test Sequence

-- Disconnect 6-pin harness connector -A- to Heated Oxygen Sensor (HO2S) 2 -G108-.

Fig 6: Identifying 6-Pin Harness Connector -A- To Heated Oxygen Sensor (HO2S) 2 -G108-

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Checking Resistance

-- Check resistance for sensor heater at connector to oxygen sensor terminal 3 +4.

Fig 7: Checking Resistance For Sensor Heater At Connector To Oxygen Sensor Terminals 3 + 4

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Specified value: Max. 10 Ω (at room temperature)

If specified value is not obtained:

-- Replace Heated Oxygen Sensor (HO2S) 2 -G108-.

-- Erase DTC memory of Engine Control Module (ECM) DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .

-- Generate readiness code READINESS CODE .

If specified value is obtained:

-- Check voltage supply and wiring to control module.

Checking Voltage Supply and Wiring

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

Fig 8: Testing Voltage Between Terminals 3 & Ground

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-- Start engine, and let run at idle.

Specified value: at least 9.0 V

-- Switch ignition off.

If specified value is not obtained:

-- Check wire from 6-pin connector terminal 3 to Power Supply Relay (Terminal 30, B+) Relay 2 -J689- according to wiring diagram: Refer to SYSTEM WIRING DIAGRAM

-- Erase DTC memory of Engine Control Module (ECM) DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .

-- Generate readiness code READINESS CODE .

If specified value is obtained:

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

Checking Ground Activation

-- Connect test box (VAG1598/42) to Engine Control Module 2 -J624- wiring harness using adapter cable (VAG1598/39-2), connecting 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 9: Identifying 6-Pin Harness Connector & Terminals

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Terminal 4 + socket 51

Wire resistance: max. 1.5Ω

-- Also check the wire for short circuit to B+ and Ground (GND).

Specified value: ∞ Ω

If no malfunctions are found in wires:

-- Replace Engine Control Module 2 -J624- ENGINE CONTROL MODULES, REPLACING .