SEAT Workshop Service and Repair Manuals > Leon Mk2 > Power unit | Manual 4-cyl. injection engine (4 valves), mechanics | Mixture preparation system, electronic inj.,Gas | Checking functions | Checking Lambda probe and Lambda control checking

Functional check

–	Connect fault reader -V.A.G 1551- (-V.A.G 1552-). Start engine and use address code 01 to select engine control unit. (Connecting fault reader and selecting engine control unit → Vehicle diagnosis, testing and information system VAS 5051.)

Indicated on display:

–	Press keys 0 and 8 for the function “Read measured value block” and confirm entry with Q key.

Rapid data transfer                 HELP

Select function XX

Indicated on display:

–	Press keys 0, 0 and 1 for “Display group number 1” and confirm entry with Q key.

Read measured value block

Input display group number XXX

Indicated on display: (1...4 = Display fields)

Only continue with the test when:

l	The coolant temperature must be at least 80 °C -display zone 2-

l	The engine has then run for a further 2 minutes at idling speed.

–	Note Lambda probe voltage in display zone 3. The voltage must fluctuate at least 30 times per minute in a range of 0.000...1.000 V

–	Press → key.

–	Press keys 0 and 6 for the “End output” function and confirm input with the Q key.

If the Lambda regulation does not fluctuate as stated:

–	Carry out road test and burn Lambda probes clean and repeat check.

Observe the valid safety precautions when carrying out a road test → Chapter.

If the specifications are not obtained again:

–	Switch off ignition.

–	Check Lambda probe heating → Chapter.

If the voltage change is slower, determine cause of fault → Chapter.

If the displayed figure remains constant:

–	Continue check according to following table:

Read measured value block 1            →

Displayed value	Cause	Continue checking
Between 0.040... 0.050 V	Open circuit	Checking basic voltage → Chapter Checking Lambda probe wiring → Chapter
0.000 V	Short to earth
1.200 V	Short to positive

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