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

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







Special tools and equipment
- VAG 1526 A
- VAG1594 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)
2 - Using the keypad -2-, enter "030" to select Display group 030 and confirm entry with Q button.
- Adjust engine speed to 2000 RPM using VAG1788/10 RPM adjuster.







Display on VAS 5051:
- Check readout in display zone -1-.

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 in this three-digit display (heating) fluctuates between 0 and 1.







Display on VAS 5051:
- Before continuing the test, wait until the readout in display zone -1- shows "111" at least once.

Testing oxygen sensor learned values and oxygen sensor control
- Press Up Arrow button twice to advance to Display group 032.
- Check readouts for oxygen sensor learned values in display zones -1- and -2-.












Display on VAS 5051:
- Press Up Arrow button to advance to Display group 033.
- Check readouts for oxygen sensor control in display zones -1- and -2-.







Note on display zone 2:
The display indicates the oxygen sensor voltage signal after it is processed and smoothed by the engine control module. A display of 1.5 V equals lambda 1.

Further Notes
If the readout in display zone 1 does not match the specification, or if the readout does not fluctuate by at least 2 %:
- Take car for a test drive to free oxygen sensor of any deposits, then repeat the test.

If the readout in display zone 1 still does not match the specification even after the test drive, or if the readout still does not fluctuate by at least 2 %:
- Test the basic voltage.
- Test the oxygen sensor heating before catalytic converter. Oxygen Sensor (O2S) Heater -Z19- (Before Catalytic Converter), Testing
- Check the oxygen sensor (before the catalytic converter) for ageing. Oxygen Sensor Aging (Before Catalytic Converter) Testing

Reading Display Group 032










Reading Display Group 033







Testing basic voltage







- Unbolt connector cover -arrows-.







- Unplug 6-pin connector -1- (black) for heated oxygen sensor (HO2S)-G39-.







- Connect multimeter (voltage measurement range) between contact 1 and 5.
- 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 heated oxygen sensor (HO2S) -G39-

Testing oxygen sensor wiring







- Unplug 6-pin connector -1- (black) for oxygen sensor (before catalytic converter) -G39.







- 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
1 70
2 71
5 51
6 52

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

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