Engines / Petrol / ME 7.5 general / Test - Lambda-sensor upstream of catalyst - voltage

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Mark	Model	Control unit	Diagnostic operation

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Model

Control unit Select the desired control unit as accurately as possible. The UDS identifier EV_xyz can be found in the VCDS after connecting to the control unit and then in the Extended Identification.

Select the desired control unit as accurately as possible. The UDS identifier EV_xyz can be found in the VCDS after connecting to the control unit and then in the Extended Identification.

Diagnostic operation Select the desired diagnostic procedure.

Diagnostic procedure

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Conditions:
- exhaust system - tightness of line - OK
- engine temperature > XX °C
- catalyst temperature > XXX °C (XX - Measured values group XXX field X)
- second mechanic necessary!

- observe the occupation safety rules when taking a test drive with connected diagnostics tester

Start the engine

wait XXX s

do a test drive - engine speed XXXX rpm - XXXX rpm

XX - Measured values group XXX

required values field X:
xxxxX = lambda control = active
xxxXx = lambda control = readiness for operation
xx?xx = heating of lambda probe(s)

upon achievement of values - engine speed = idling

XX - Measured values group XXX
required values
field X = -XX% - +XX% - fluctuates (lambda control value)
field X = X,XV - X,XV - fluctuates (voltage of lambda probe(s))

if values are not achieved - field X < -XX% - rich mixture - check component:
- injector - tightness of line
- fuel pressure - high
- spark-plugs
- electromagnetic valve for the active carbon box - open
- heating of lambda probe(s)
- Lambda sensor(s)

if values are not achieved field X > +XX% - poor mixture - check component:
- exhaust system - tightness of line
- fuel pressure - low
- injector - clogged
- heating of lambda probe(s)
- Lambda sensor(s)

if values are not achieved field X = X - emergency mode -check component:
- exhaust system - tightness of line
- engine speed - idling
- injector - clogged, tightness of line
- spark-plugs
- electromagnetic valve for the active carbon box - open
- heating of lambda probe(s)
- Lambda sensor(s)

if values are not achieved field X - check component:
- Lambda sensor(s) line - short-circuit to GND ???
- Lambda sensor(s) - replace

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