Oxygen Sensors and O2 Sensor Regulation Before (TWC), Check

Functions, checking

Check oxygen sensors and oxygen sensor regulation before catalytic converter


NOTE:
- When servicing terminals in harness connector of oxygen sensors, use only gold-plated terminals.
- The oxygen sensors before catalytic converter have a constant regulation and can be differentiated from the oxygen sensor behind catalytic converter via a 6-pin connector.

- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram


Test requirements







The respective fuses of Heated Oxygen Sensor (HO2S) -G39- and Heated Oxygen Sensor (HO2S) 2 -G108- must be OK.







- Fuses -1, 2, 3, 4 and 7- in protective housing (plenum chamber, left) must be OK
- 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 position -P-or -N-.
- If vehicle is equipped with an A/C system, it must be switched off.
- Ground (GND) connections between engine and chassis must be OK.
- Exhaust system must be properly sealed between catalytic converter module and cylinder head.
- Coolant temperature must be at least 80 degrees C, Diagnostic mode 1: Check measuring values; PID 5, Coolant temperature. Refer to "Scan Tool Testing/Diagnostic Mode 1: Check Measuring Values".
Diagnostic Mode 1: Check Measuring Values

- Oxygen sensor heaters for oxygen sensors before catalytic converter must be OK, check
Oxygen Sensors and O2 Sensor Regulation Before (TWC), Check

Function test
- Select the lambda test results and check whether the specified values are being reached, Diagnostic mode 5: Check output of oxygen sensor signals. Refer to "Scan Tool Testing/Diagnostic Mode 5: Check Output of Oxygen Sensor Signals"
Diagnostic Mode 5: Check Output of Oxygen Sensor Signals
- End diagnostic and switch ignition off.

If specified values are not obtained:

Checking oxygen sensor wires
- Connect test box to control module wiring harness, connect test box for wiring test. Refer to "Scan Tool Connecting/Test Box, Connecting For Wiring Test". Test Box, Connecting For Wiring Test







- Disconnect 6-pin harness connector to the respective oxygen sensor:
- Heated Oxygen Sensor (HO2S) -G39-, bank 1 6-pin harness connector (black) -1-,
- Heated Oxygen Sensor (HO2S) 2 -G108-, bank 2 6-pin harness connector (brown) -2-.


NOTE:
- Bank 1 = Cylinder bank 1, in direction of travel, right
- Bank 2 = Cylinder bank 2, in direction of travel, left







- Check wires between test box and 6-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Wire resistance: max. 1.5 Ohms







- Also check wires for short circuit to B+ and Ground (GND).
Specified value: Infinity Ohms

If no malfunctions are found in wires:
- Replace the respective oxygen sensor:
- Bank 1 Heated Oxygen Sensor (HO2S) -G39-, item 3
- Bank 2 Heated Oxygen Sensor (HO2S) 2 -G108-, item 9

- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Refer to "Monitors, Trips and/or Drive Cycle/Readiness Code, Generating". Monitors, Trips, Drive Cycles and Readiness Codes