Oxygen Sensor and Oxygen Sensor Control (After Catalytic Converter), Testing

Oxygen Sensor And Oxygen Sensor Control (after Catalytic Converter), Testing

NOTE: The oxygen sensor before catalytic converter (Bank 1, Probe 1) holds the value at lambda = 1. If the function of this oxygen sensor is impaired due to dirt or overheating, the controlled value can alter. The oxygen sensor after catalytic converter (Bank 1, Probe 2) detects any deviations from lambda = 1. It corrects variations (positive or negative) by increasing or reducing the oxygen sensor control before catalytic converter accordingly.







Special tools and equipment
- VAG 1526 A
- VAG 1594 A
- VAG 1598/31
- VAG 1788/10
- VAS 5051 with VAS 5051/1

Requirements for test:
- Exhaust system free of leaks
- Coolant temperature at least 80 degrees C

Test sequence
Connect the vehicle diagnostic, testing and information system VAS 5051, Vehicle Diagnostic, Testing and Information System VAS 5051, Connecting and Selecting Functions , and select the vehicle system "01 - Engine electronics" from the menu. When doing this the engine should be idling.







Display on VAS 5051:
- Select the diagnosis function "04 - Basic settings" from the menu -1-.







Display on VAS 5051:
1 - Enter display group
(figures up to 255)
- Using the keypad -2-, enter "030" to select Display group 030 and confirm entry with Q button.
- Set engine speed to 2000 RPM using VAG1788/10 RPM adjuster.







Display on VAS 5051:
- Check readout in display zone -2-.

NOTE:
- The specified readouts can be obtained more quickly by increasing the engine speed.
- The "oxygen sensor status" indicates the status of the oxygen sensor control and the oxygen sensors.












NOTE:
- The first digit of the three-digit display (heating) fluctuates between 0 and 1.
- The oxygen sensor control of oxygen sensor (after the catalytic converter; B1-P2) is not active when the engine is not running under load.







Display on VAS 5051:
- Before continuing the test, wait until the readout in display zone -2- shows "110" at least once.

Testing oxygen sensor control (after catalytic converter)

Requirement
- Engine idling at 2000 RPM.

- Press the <- button.







Display on VAS 5051:
1 - Enter display group
(figures up to 255)
- Using the keypad -2-, enter "037" to select Display group 037 and confirm entry with Q button.







Display on VAS 5051:
- Check oxygen sensor voltage in display zone -2-:
- Check the compensating value of the oxygen sensor control in display zone -3- and the result of the diagnosis in display zone -4-.







Reading Display Group 037







Further notes
If the readout in display zone 3 or 4 does not match the specification:
- Take car for a test drive to free oxygen sensor of any deposits, then repeat the test.

If the readout in display zone 3 or 4 still does not match the specification even after the test drive:
- Replace the oxygen sensor (before the catalytic converter) -G39.

NOTE: If the oxygen sensor voltage is OK and the compensating value is still above 0.02 even after a test drive, this points to excessive aging of the oxygen sensor before catalytic converter.

Testing basic voltage







- Unbolt connector cover -arrows-.







- Unplug 4-pin connector -1- (brown) for oxygen sensor (O2S) behind three way catalytic converter (TWC) -G130-.







- Connect multimeter (voltage measurement range) between contacts 3 and 4.
- Switch ignition on.
- Specification: 0.400 to 0.500 V
- Switch off ignition.

If the specification is not obtained:
- Test oxygen sensor wiring.

If the specification is obtained:
- Replace the oxygen sensor (O2S) behind three way catalytic converter (TWC) -G130-.

Testing oxygen sensor wiring







- Unplug 4-pin connector -1- (brown) for oxygen sensor (O2S) behind three way catalytic converter (TWC) -G130-.
- Connect test box VAG 1598/31 to wiring harness for engine control module. Do not connect to the engine control module itself. Scan Tool Testing and Procedures







- Test the following wiring connections for open circuits:

Connector Contact Test box VAG 1598/31 Socket
3 68
4 69

- Correct any open circuits.
- Test for short circuits between the wires.

If the wiring is OK:
- Install a new engine control module.