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Checking vent frame > < Mode of operation of air quality sensorG238

A3 Mk2

Checking air quality sensorG238
Checking air quality sensor -G238-
Special tools and workshop equipment required
t  Vehicle diagnostic, testing and information system -VAS 5051 A- with diagnostic wire -VAS 5051/5A-
t  Commercially available gas cigarette lighter
Test requirements
t  Vehicle standing in a clean atmosphere (away from running engines, exhaust vents, etc.)
t  Engine compartment and plenum chamber clean (not contaminated with oil or fuel)
t  Engine compartment and plenum chamber not sprayed with cleaning agents or preservatives containing solvents
Checking
–  With the ignition switched off, connect up the vehicle diagnostic, testing and information system -VAS 5051 A- with the diagnostic cable -VAS 5051/5A- to the diagnostic connection in the vehicle → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
–  Start the engine.
–  Interrogate the event recorder of the operating and display unit, Climatronic control unit -J255- → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
–  On the operating and display unit, Climatronic control unit -J255-, set „Auto“ mode.
–  On the operating and display unit, Climatronic control unit -J255-, activate the „automatic air recirculation“ function.
–  Wait 30 s to allow the air quality sensor -G238- to warm up.
–  By way of the vehicle diagnostic, testing and information system -VAS 5051 A-, select the „Reading measured value block“ function → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
–  Read out the measured values for the air quality sensor -G238-.
  Note
The measured value block shows the operating status of the fresh-air/air recirculation flap and the status of the air quality sensor -G238- signal → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
t  Specification: No request for „air recirculation mode“ (air conditioner in fresh-air mode)
Or
t  Specification: No request for „air recirculation mode“, request for „partial air recirculation mode“ (fresh-air/air recirculation flap roughly in centre position)
–  Remove the air quality sensor -G238- from the mount → Chapter.
   
–  Allow a small quantity of gas from a cigarette lighter -B- to flow from above past area -A- of the air quality sensor -G238-.
  Note
t  There are different housings for and versions of the air quality sensor -G238-. Attention is therefore to be paid to the correct assignment → Electronic parts catalogue.
t  The air quality sensor -G238- reacts when exposed to cigarette smoke or cigarette lighter gas. As cigarette lighter gas is heavier than air, the air quality sensor -G238- is to be removed and the gas applied from above.
–  Read the display:
t  Specification: („Automatic air recirculation mode“ requested, request met, air conditioner switches to air recirculation mode).
–  Wait briefly (approx.1 minute, depending on the amount of test gas sprayed onto the air quality sensor -G238-).
–  Read the display:
t  Specification (no request for „air recirculation mode“, air conditioner in fresh-air mode)
Or
t  Specification: No request for „automatic air recirculation mode“, partial air recirculation mode requested.
  Note
To stop the fresh-air/air recirculation flap being switched too frequently, an air quality sensor -G238- request for „automatic air recirculation mode“ is applied for at least 25 s (minimum dwell time) even if the pollutant concentration in the air has decreased to such an extent that air recirculation mode would no longer be necessary.
–  Actuate the windscreen wash/wipe switch until the washer pump -V5- has conveyed fluid for approx. 2 s.
–  Read the display:
t  Specification: („Air recirculation mode“ requested on account of windscreen washer system, air conditioner switches to air recirculation mode for approx. 10 sec.).
–  Wait briefly.
–  Read the display:
t  Specification: (No request for „air recirculation mode“, air conditioner in fresh-air mode)
Or
t  Specification: No request for „automatic air recirculation mode“, partial air recirculation mode active.
  Note
t  Depending on the composition of the windscreen washer fluid, the air quality sensor -G238- may detect air pollution and request „Automatic air recirculation mode“.
t  If switching to air recirculation mode does not take place on actuating the windscreen wipe/wash switch, check operation („windscreen wash“ information is received via convenience data bus system from steering column electronics control unit -J527-) → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
Proceed as follows if the air quality sensor -G238- functions properly in this test but a customer complaint has been received:
–  Check for contamination of the dust and pollen filter → Chapter.
–  Connect up the fault reader and select the function „Guided fault-finding“ → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
–  A second person is required, as the display values have to be read out whilst driving.
–  Heed the safety instructions → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
–  Read out the measured value of the air quality sensor -G238- → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
–  Start by driving the vehicle into an area with a relatively clean atmosphere (system in fresh-air mode).
–  Then drive into a polluted area (e.g. uphill road with lorry traffic).
–  Read off the displays in the display zones. The display in the display zones must change, for example when driving through a cloud of diesel emissions. → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
–  Refer also to → Chapter „Dust and pollen filter with activated charcoal element“ and → Chapter „Mode of operation of air quality sensor -G238-“ for description.
  A87-10605

Checking vent frame > < Mode of operation of air quality sensorG238