Oxygen Sensors and Control Before Catalytic Converter
Function Tests
Check Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter
NOTE: The oxygen sensor before catalytic converter (bank 1, sensor 1 or bank 2, sensor 1) holds the value at Lambda = 1. If this oxygen sensor is damaged, e.g. due to dirt or overheating, the controlled value may have shifted. Deviations from Lambda = 1 are detected by the oxygen sensor behind catalytic converter (bank 1, sensor 2 or bank 2, sensor 2). If it recognizes the deviations downward or upward, it influences the regulation before catalytic converter, generally increasing or decreasing it respectively.
Recommended special tools and equipment
- VAG1526A multimeter
- VAG1594A connector test kit
- VAG1598/31 test box
Test requirements:
- Fuses for engine electronics OK
- Ground (GND) connections at engine and transmission OK
- Oxygen sensor heater OK; check. Oxygen Sensor After Catalyst Checking
- Exhaust system free of leaks.
- Parking brake engaged.
- Vehicles with automatic transmission Selector lever 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 degree C "Mode 1: Check measuring values "; "PID 05: Coolant temperature". Diagnostic Mode 1: Check Measured Values
Procedure
- Connect diagnostic tester. Diagnostic Tester, Connecting
- Start engine and let run at idle.
- In diagnostic function "33 - OBD", select "Mode 5: Check output of oxygen sensor signals".
NOTE:
- Bank 1 see cylinder bank 1 in direction of travel, right; Bank 2 see 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 output of oxygen sensor signals, the respective oxygen sensor can be selected by pressing button 1, 2, 5 and 6:
- Button 1 see Bank 1 sensor 1,
- Button 2 see Bank 1 sensor 2,
- Button 5 see Bank 2 sensor 1,
- Button 6 see Bank 2 sensor 2.
- Select the desired output of oxygen sensor signals according to the following table.
Test-ID 07 - 08:
- Check values of output for oxygen sensor signals.
*)V = Voltage in Volts (oxygen sensor signal)
**)t = Time in seconds
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:
Checking primary voltage
- Disconnect electrical 4-pin harness connector -3- from Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- and Oxygen Sensor (O2S) Heater 1 behind Three Way Catalytic Converter (TWC) -Z29- (bank 1, sensor 2).
- Disconnect electrical 4-pin harness connector -1- from Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131- and Oxygen Sensor (O2S) Heater 2 -Z30- (bank 2, sensor 2).
NOTE: To reach the harness connectors, the left cover in engine compartment must be removed, the line to Engine Coolant Level (ECL) Warning Switch at bottom on reservoir must be disconnected, and the bolt -arrow- of the coolant reservoir must be unscrewed and set aside. Coolant hoses -1- to -3- remain connected.
- Connect multimeter between terminal 3 and 4 for voltage measurement.
- Switch ignition on.
- Specified value: 0.400 ... 0.500 V
- Switch ignition off.
If specified value is not obtained:
- Check oxygen sensor wires, See Bank 1 and Bank 2.
If specified value is obtained:
- Replace respective oxygen sensor behind catalytic converter.
Check oxygen sensor wires for Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- (bank 1, sensor 2)
- Connect test box to wiring harness of Engine Control Module (ECM); ECM is not connected. Text Box, Connecting For Wiring Test
- Check the following wire connections for open circuit according to wiring diagram:
Harness connector Test box
Terminal Socket
3 68
4 69
- Specified value: Wire resistance max 1.5 Ohm
- Also check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: infinity Ohm (no continuity)
- If necessary, repair wire connection.
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).
Check oxygen sensor wires for Oxygen Sensor (O2S) 2Behind Three Way Catalytic Converter (TWC) -G131- (bank 2, sensor 2)
- Connect test box to wiring harness of Engine Control Module (ECM); ECM is not connected. Text Box, Connecting For Wiring Test
- Check the following wire connections for open circuit according to wiring diagram:
Harness connector Test box
Terminal Socket
3 10
4 11
- Specified value: Wire resistance max 1.5 Ohm
- Also check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: infinity Ohm (no continuity)
- If necessary, repair wire connection.
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1 - Check DTC memory, "Mode 3: Check DTC memory". Diagnostic Mode 3: Check DTC Memory
2 - If necessary, erase DTC memory, "Mode 4: Reset/erase diagnostic data". Diagnostic Mode 4: Check Reset/Erase Diagnostic Data
3 - Generate readiness code. Readiness Code, Generating