Heated Oxygen Sensor Ho2S, Checking

Observe all safety precautions: SAFETY PRECAUTIONS 

View clean working conditions: CLEAN WORKING CONDITIONS 

For wiring diagrams, component locations, and connector views, Refer to the applicable wiring diagram.

Special tools and workshop equipment required 

• Multimeter.
• Wiring diagram.

Test requirements 

• The Heated Oxygen Sensor (HO2S) - G39- fuse OK.
  Fig 1: Identifying Fuses On E-Box In Engine Compartment, Left Side

  Courtesy of AUDI OF AMERICA, LLC
• The Oxygen Sensor Heater - Z19- before catalytic converter OK. Refer to OXYGEN SENSOR HEATER, CHECKING .
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.
• A/C switched off.
• Ground (GND) connections between engine/transmission/chassis OK.
• Exhaust system between catalytic converter and cylinder head properly sealed.
• Coolant Temperature at least 80 °C.

Test procedure 

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK 

Start diagnosis 

-- Remove the engine cover with air filter. Refer to appropriate service information.

Checking Internal Resistance 

-- Disconnect the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector -1-.

-- Using a Multimeter, check the Heated Oxygen Sensor (HO2S) - G39- electrical harness connector -1- terminals 3 to 5 for correct resistance.

Specified value: 2.5 to 10.0 Ω

If the specified value was Not obtained:

-- Replace the Heated Oxygen Sensor (HO2S) - G39-. Refer to the appropriate service information.

-- Go to Final procedures

If the specified value was obtained:

Checking wiring 

If the manufacturers test box is being used, perform the following step.

-- Install the test box.

If the manufacturers test box is not being used, perform the following step.

-- Remove the Motronic Engine Control Module (ECM) - J623 -. Refer to the appropriate service information.

-- Using a Multimeter, check the Heated Oxygen Sensor (HO2S) - G39- electrical harness connector terminals to the Motronic Engine Control Module (ECM) - J623- electrical harness connector T94 terminals for an open circuit.

Heated Oxygen Sensor (HO2S) - G39- electrical harness connector terminals	Motronic Engine Control Module (ECM) - J623- electrical connector T94 terminals or test box sockets
1	78
2	79
5	56
6	57

Specified value: 1.5 Ω Max.

If the specified value was Not obtained:

-- Check the circuits for a short to each other, short to battery voltage, and short to ground.

-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

-- Repair the wiring or connection as necessary.

-- Go to Final procedures

If the specified value was obtained:

-- Replace the Motronic Engine Control Module (ECM) -J623-. Refer to the appropriate service information.

Final procedures 

-- Reinstall the engine cover with air filter. Refer to appropriate service information.

-- After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .