Audi Workshop Service and Repair Manuals

Note:

The lambda probe upstream of catalytic converter (Bank 1, probe 1) changes to Lambda 1. If this lambda probe is damaged, e.g. through contamination or overheating, the control value can be changed. Deviations from Lambda 1 is recorded by the lambda probe downstream of the catalytic converter (Bank 1, Probe 2). If these deviations are recognised downwards or upwards it influences the control upstream of the catalytic converter in such a way that it is generally raised or lowered accordingly.

Special tools and workshop equipment required

• ◆ V.A.G 1526 A
• ◆ V.A.G 1594 A
• ◆ V.A.G 1598/31
• ◆ V.A.G 1788/10
• ◆ VAS 5051 with VAS 5051/1

• or

• ◆ V.A.G 1551 with V.A.G 1551/3 A

Test requirements:

• ● No leaks in exhaust system.
• ● Coolant temperature at least 80 °C.

Test sequence

• ‒ Connect up vehicle diagnosis, measurement and information system VAS 5051 or fault reader V.A.G 1551 and select engine electronics control unit with "Address word" 01 .
  For this purpose, the engine must be running at idle speed
• ‒ Adjust speedometer V.A.G 1788/10 on accelerator pedal and increase speed to 2600 rpm.

Test conditions:

• ● Engine runs at 2600 rpm.

• ‒ Enter "04" to select "Start basic setting" and confirm with Q key.

• ‒ Enter "030" for "display group number 030" and confirm entry with Q key.
• ‒ Check Lambda probe status in display zone 2.

Note:

The "lambda probe status" indicates the condition of the lambda control and the lambda probes.

Notes:

• ◆ The first digit of the 3-digit display (heating) fluctuates between 0 and 1.
• ◆ The lambda control of the lambda probe downstream of catalytic converter (B1-S2) is inactive without engine load.

• ‒ Only continue the test if the display in display zone 2 has reached "110" at least once.

Checking lambda control after catalytic converter

Test conditions:

• ● Engine continues running at 2600 rpm.

• ‒ Press C key.

• ‒ Enter "037" for "display group number 037" and confirm entry with Q key.

• ‒ Check lambda probe voltage in display zone 2.
• ‒ Check lambda correction value in display zone 3 and the diagnosis result in display zone 4.

Note on display zone 2:

The lambda probe voltage Bank 1, probe 2 should be kept as constant as possible. Strong voltage fluctuations indicate a damaged catalytic converter.

Interpreting display group 037

(cont.)

If specified value in display zone 3 or 4 is not attained:

• ‒ Perform test drive to free Lambda from any possible residues and repeat the test.

If specified value in display zone 3 or 4 is not attained, even after a test drive has been performed:

• ‒ Replace the lambda probe upstream of catalytic converter -G39.

Note:

If the lambda probe voltage is OK and the lambda correction value is still above 0.02 even after test drive was performed it indicates an aged lambda probe upstream of catalytic converter.

Checking basic voltage

• ‒ → Unplug 4-pin connector -1- (brown) to lambda probe upstream of catalytic converter -G130.

Note:

To gain access to the connector screw out coolant expansion tank bolts and swivel expansion tank aside. Fuel hoses remain connected.

• ‒ → Connect multimeter between contacts 3 and 4 to measure voltage.
• ‒ Switch the ignition on.
• ‒ Specified value: 0.400...0.500 V
• ‒ Switch ignition off.

If specified value is not attained:

• ‒ Check the Lambda probe lines.

If specified value is attained:

• ‒ Replace lambda probe downstream of catalytic converter -G130.

Check lambda probe wiring

• ‒ → Unplug 4-pin connector -1- (brown) to lambda probe upstream of catalytic converter -G130.

Note:

To gain access to the connector screw out coolant expansion tank bolts and swivel expansion tank aside. Fuel hoses remain connected.

• ‒ Connect the V.A.G 1598/31 test box to wiring harness leading to engine control unit; the engine control unit should not be connected => Page 24-19.

• ‒ → Test for open circuit in the following wiring connections.

• ‒ Rectify open circuit, if necessary

=> Current Flow Diagrams, Electrical Fault-Finding and Fitting Locations

• ‒ Check for shorts between the two lines.

If the wiring is OK:

• ‒ Fit a new engine control unit => Page 24-23.