Volkswagen Workshop Service and Repair Manuals

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

• ◆ Fault reader V.A.G 1551 (or vehicle system tester V.A.G 1552) with cable V.A.G 1551/3

• ◆ → V.A.G 1788/10 Engine speed adjuster

Test conditions

• ● Vehicle stationary
• ● On vehicles with automatic gearbox selector lever in "P" or "N" position
• ● All electrical consumers, e.g. lights and rear window heating must be switched off.
• ● Intake air temperature less than 60°C
  =>display group 04, display zone 4
• ● Coolant temperature must be min. 60 °C, =>display group 04, display zone 3.

Work sequence

• ‒ Connect the fault reader V.A.G 1551 (V.A.G 1552). Then switch ignition on and select engine control unit with the "Address word" 01.
  (Connecting fault reader and selecting engine control unit .)

Work step 1: Interrogate fault memory

• ‒ Press keys 0 and 2 for function "Interrogate fault memory" and confirm entry with Q key.

If a fault is stored:

• ‒ Rectify faults printed out using fault table:
  SAE P0 codes=> Page 01-33

If no fault is stored:

• ‒ Press ⇒key.

Work step 2: Erase fault memory

• ‒ Press keys 0 and 5 for the function "Erase fault memory" and confirm entry with Q key.

Note:

The readiness code is reset or erased each time fault memory is erased.

Note:

If the ignition is switched off between "Interrogate fault memory" and "Erase fault memory" the fault memory will not be erased.

• ‒ Press ⇒key.

Work step 3: Matching the throttle valve control part to the engine control unit

• ‒ Press keys 0 and 4 for the function "Introduction of basic setting" and confirm entry with Q key.

• ‒ Press keys 0, 6 and 0 for the "Display group number 60" and confirm entry with Q key.

• ‒ Check specifications in display zones 3 and 4:
       Display zone 3: Idling speed
       Display zone 4: ADP. runs, ADP. OK.
• ‒ Terminate engine basic setting at earliest after 30 seconds by pressing the⇒ key.

If the display does not indicate as described:

• ‒ Check throttle valve control part
  => Page 24-40 .

If the display indicates as described:

• ‒ Start engine and run at idling speed.

Note:

• ◆ During the work sequence the engine must not be switched off.

Work step 4: Secondary air system diagnosis

• ‒ Press keys 0 and 4 for the "Introduce basic setting" function and confirm entry with Q key.

• ‒ Press keys 0, 7 and 7 for the "Display group number 77" and confirm entry with Q key.

If the diagnosis is initiated from engine control unit the display in display zone 4 jumps from "Test OFF" to "Test ON"

• ‒ Allow the engine to continue running at idling speed until the
       specification "Syst. OK."
  is displayed in display zone 4.

If the display does not indicate as described:

• ‒ Interrogate fault memory => Page 01-17 .

If the display indicates as described:

• ‒ Press C key.

Work step 5: Activated charcoal filter system diagnosis (tank venting system)

• ‒ Press keys 0, 7 and 0 for "Display group number 70" and confirm entry with Q key.

When the diagnosis is initiated by the engine control unit the display in display zone 4 jumps from "Test OFF" to "Test ON"

• ‒ Run engine at idling speed until the
       specification "TVV OK"
  is displayed in display zone 4.

If the display does not indicate as described:

• ‒ Interrogate fault memory => Page 01-17 .

If the display indicates as described:

• ‒ Press ⇒key.

Work step 6: Lambda probe ageing diagnosis (cycle duration monitor)

• ‒ Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

• ‒ Press keys 0, 3 and 4 for "Display group number 34" and confirm entry with Q key.

• ‒ Set an engine speed of 2200...2800 rpm with speed regulator V.A.G 1788/10:

• ‒ Maintain speed at 2200...2800 rpm until the catalyst temperature in
       display zone 2 exceeds 352 °C.

Note:

This process can take a few minutes.

• ‒ Press C key.

• ‒ Press keys 0, 3 and 0 for the "Display group number 30" and confirm entry with Q key.

• ‒ Check the operating condition of the Lambda control in front of catalyst (display zone 1):
       Specification: 111
• ‒ Check the operating condition of the Lambda regulation after catalyst (display zone 2):
       Specification: 111

Note:

The Bits in display zone 2 are set to 1 first when the catalyst temperature exceeds 352 °C (=> display group 34, display zone 2).

Significance of 3 digit number block in display zones 1 and 2:

If the specifications are not obtained:

• ‒ Interrogate fault memory => Page 01-17 .

If the specifications are obtained:

• ‒ Set an engine speed of 2200...2800 rpm with speed regulator V.A.G 1788/10:
• ‒ Press ⇒key.

• ‒ Press keys 0 and 4 for the "Introduce basic setting" function and confirm entry with Q key.

• ‒ Press keys 0, 3 and 4 for "Display group number 34" and confirm entry with Q key.

• ‒ Maintain the engine speed at 2200...2800 rpm until the display in
       display zone 4 jumps from "Test OFF" to "Test ON".
  The catalyst temperature in
       display zone 2 must be min. 352 °C.
• ‒ Check the time period in display zone 3:
       Specification: max. 2.2 seconds
• ‒ Continue to maintain the speed at 2200...2800 rpm until
  the specification "B1-P1 OK" appears in
       display zone 4.

If the specifications are not attained:

• ‒ Interrogate fault memory => Page 01-17 .

If the specification is obtained:

• ‒ Press C key.

Work step 7: Catalyst diagnosis

Note:

The diagnosis will only be terminated if the Lambda probe ageing diagnosis is first successfully completed.

• ‒ Press keys 0, 4 and 6 for "Display group number 46" and confirm entry with Q key.

• ‒ Increase the engine speed at 2800...3200 rpm until the display in
       display zone 4 jumps from "Test OFF" to "Test ON".
  The catalyst temperature in
       display zone 2 must be min. 352 °C.
• ‒ Check the amplitude ratio in display zone 3:
       Specification: max. 0.55
• ‒ Continue to maintain the speed at 2800...3200 rpm until the
       Specification "Cat B1 OK" appears in
       display zone 4.

Note:

The diagnosis of the catalyst takes approx. 100 seconds. If there is still no result in the display after 150 seconds, change the speed within the tolerance.

• ‒ Remove the engine speed adjuster V.A.G 1788/10 from accelerator pedal.
• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the "End output" function and confirm input with the Q key.

If the display does not indicate as described:

• ‒ Interrogate fault memory => Page 01-17 .

If the display indicates as described:

• ‒ Press ⇒key.
• ‒ Read readiness code=> Page 01-57