Oxygen Sensors and Oxygen Sensor Control Before Catalytic Converter, Checking
Oxygen Sensors And Oxygen Sensor Control Before Catalytic Converter, Checking
Recommended special tools and equipment
- V.A.G 1526A multimeter
- V.A.G 1594A connector test kit
- V.A.G 1598/31 test box
Test requirements:
- Fuses for engine electronics OK
- Ground (GND) connections at engine and transmission OK
- Oxygen sensor heater OK; check.
- Exhaust system free of leaks.
- Parking brake engaged.
- Selector lever of automatic transmission in position "P" or "N".
- Electrical consumers switched off (radiator fan must NOT run during test).
- A/C switched off.
- Coolant temperature at least 80 degrees C see "Mode 1: Check measuring values "; "PID 05: Coolant temperature". Mode 1: Check Measured Values
Procedure
NOTE:
- Bank 1 = cylinder bank 1 in direction of travel, right; Bank 2 = cylinder bank 2 in direction of travel, left.
- When selecting the diagnostic mode, the entry is always performed in "Bank 1 sensor 1".
- If the Vehicle Diagnostic, Testing and Information System VAS 5051 or the Vehicle Diagnostic and Information System VAS 5052 is used for checking the lambda test results, the respective oxygen sensor can be selected by pressing button 1, 2, 5 and 6.
- Button 1 = Bank 1 sensor 1,
- Button 2 = Bank 1 sensor 2,
- Button 5 = Bank 2 sensor 1,
- Button 6 = Bank 2 sensor 2.
- When servicing terminals in harness connector of oxygen sensor, use only gold-plated terminals.
- Connect diagnostic tester.
- Start engine and let run at idle.
- In diagnostic function "33 - OBD", select "Mode 5: Check output of oxygen sensor signals".
- Select the desired output of oxygen sensor signals according to the following table.
- Check values of output for oxygen sensor signals.
If specified values are not obtained:
- Road test vehicle in order to free oxygen sensors of possible residue and repeat test.
If specified values are not obtained again:
- Test oxygen sensor heater before catalytic converter
- Check intake system for leaks (false air). Intake System For Leaks (False Air), Checking
- Check Oxygen Sensor (O2S) and oxygen sensor control behind Three Way Catalytic Converter (TWC). Check Oxygen Sensor and Oxygen Sensor Control Behind Catalytic Converter
- Check fuel pressure regulator and residual pressure. Fuel Pressure Regulator and Holding Pressure, Checking
- Check fuel injectors. Check Fuel Injectors
- Check Evaporative Emission (EVAP) Canister Purge Regulator Valve -N80-. Evaporative Emission (EVAP) Canister Purge Regulator Valve -N80-, Checking
- Check Fuel Pump (FP) -G6-. Fuel Pump (FP), Electrical Testing
- Check exhaust system for proper seal. Exhaust System For Proper Seal, Checking
- Check Secondary Air Injection (AIR) system for proper seal. Secondary Air Injection (AIR) System, Checking For Proper Seal
- Check vacuum lines for leaks.
- Connect test box at wiring harness to Engine Control Module (ECM), do not connect ECM. Test Box, Connecting For Wiring and Component Test
Check oxygen sensor wires for Heated Oxygen Sensor (HO2S) -G39- (bank 1, sensor 1)
- Disconnect electrical 6-pin harness connector -2- at right from Heated Oxygen Sensor (HO2S) -G39- (before catalytic converter) and Oxygen Sensor (O2S) Heater -Z19- (bank 1, sensor 1).
- Check the following wire connections for open circuit according to wiring diagram.
Harness connector Test box Socket
Terminal
1 70
2 71
5 51
6 52
Specified value: Wire resistance max 1.5 Ohms
- Check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: Infinite Ohms (no continuity)
- If necessary, repair wire connection.
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).
Checking oxygen sensor wires for Heated Oxygen Sensor (HO2S) 2 -G108- (bank 2, sensor 1)
- Remove coolant reservoir -2- -arrows-.
- Disconnect electrical wire from Engine Coolant Level (ECL) Warning Switch -F66- and set aside coolant reservoir with coolant hoses -1- and -3- connected.
- Disconnect electrical 6-pin harness connector -1- to left from Heated Oxygen Sensor (HO2S) 2 -G108- (before catalytic converter) and Oxygen Sensor (O2S) 2 Heater 2 -Z28- (bank 2, sensor 1).
- Check the following wire connections for open circuit.
Harness connector Test box Socket
Terminal
1 13
2 14
5 12
6 15
Specified value: Wire resistance max 1.5 Ohms
- Check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: Infinite Ohms (no continuity)
- If necessary, repair wire connection.
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).
Assembly is performed in reverse order of removal, note the following:
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check DTC memory see "Mode 3: Check DTC memory". Mode 3: Check DTC Memory
2. If necessary, erase DTC memory see "Mode 4: Reset/erase diagnostic data". Mode 4: Reset/Erase Diagnostic Data
3. Generate readiness code. Readiness Code, Generating
- End diagnosis and switch ignition off.