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Climate Control Exhaust Gas Sensor: Testing and Inspection






Air Quality Sensor, Checking

Special tools, testers and auxiliary items required

• Vehicle Diagnostic, Testing and Information System (VAS 5051) with diagnostic cable (VAS 5051/5A)

• Test gas (D 007 855 A2) or a commercially available gas lighter

Test Requirements

• Vehicle standing in a clean atmosphere (away from running engines, exhaust vents, etc.)

• Engine compartment and plenum chamber clean (not contaminated with oil or fuel)

• Engine compartment and plenum chamber not sprayed with cleaning agents or preservatives containing solvents

Checking

- With the ignition switched off, connect the Vehicle Diagnosis, Testing and Information System (VAS 5051) with the Diagnostic Cable (VAS 5051/5A) to the 16-pin data link connector on the vehicle => Vehicle Diagnosis, Testing and Information System VAS 5051.

- Start the engine.

- Check DTC memory of A/C control head Climatronic Control Module (J255). => Vehicle diagnosis, testing and information system VAS 5051

- Set the Climatronic Control Module (J255) A/C control head ("Comfort" system) to "Auto".

- Using the MMI (Multi Media Interface) at the Climatronic Control Module (J255)A/C control head or the rotary push-button on the MMI control module, switch on the "Automatic Recirculation" mode (different versions) => Owner's Manual and => Owner's Manual"Infotainment / MMI".

- Wait 30 seconds (warm up time for Air Quality Sensor (G238)).

- Using the Vehicle Diagnosis, Testing and Information System (VAS 5051) select "Read Measured Value Block" => Vehicle Diagnosis, Testing and Information System VAS 5051.

- Read out the measured values for the Air Quality Sensor (G238) and the recirculating/fresh air door position => Vehicle Diagnosis, Testing and Information System VAS 5051 in the "Guided Fault Finding" function.

• The A/C system operating status (position of the recirculating/fresh air door) and the status of the signal from the Air Quality Sensor (G238) are displayed. Explanation of the possible displays => vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.

• Specification: no request for "Recirculation Mode", A/C system in fresh air mode (request for the recirculating/fresh air door position) => Vehicle Diagnosis, Testing and Information System VAS 5051 in the "Guided Fault Finding" function.

Or

• Specification: "Partial Recirculation Mode" (recirculating/fresh air door position open).

Test procedure "1"

- Remove the air quality sensor (G238) from the mount.

- Allow a little bit of gas from the lighter to flow by area - A - on the air quality sensor (G238) from above.





• If the Air Quality Sensor (G238) comes in contact with cigarette smoke or with gas from an ignitor, it will react since ignitor gas is heavier than air; remove the Air Quality Sensor (G238).

Test procedure "2"

- Place spray head - A - of test gas bottle over air inlet of air quality sensor - B -.





- Press spray head - C - of test gas bottle for 1 second.

• There are different versions of the air quality sensor (G238), each with different functions. Make sure the allocation is correct.

• The test gas canister is filled with pure oxygen with a specific nitrogen oxide component.

• If cigarette smoke or cigarette lighter gas (gas is heavier than air, therefore remove the Air Quality Sensor (G238) and turn it around) acts on the Air Quality Sensor (G238), it also reacts.

Continuation for both test procedures

- Read the display with the air quality sensor (G238) measured value and the recirculating/fresh air flap position => vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.

• The specified value for the recirculating and fresh air door position changes from fresh air or partial recirculation mode when there is a request for "Automatic Recirculation Mode". The request is fulfilled (the A/C system switches to recirculation mode).

- Wait a short period time (approximately 1 minute, depending on amount of test gas sprayed in sensor).

- Read the display with the air quality sensor (G238) measured value and the recirculating/fresh air flap position => vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.

• The specified value for the recirculating/fresh air door position changes from recirculation mode to fresh air or partial recirculation mode (no request for "Recirculation Mode" present, A/C system in fresh air or partial recirculation mode).

• In order to avoid frequent opening/closing of the fresh air doors and the recirculation doors, the Air Quality Sensor (G238) request for "Automatic Air Recirculation" mode remains for at least 25 seconds (minimum duration period), even if the pollutant concentration reduces to the point that recirculated air mode is no longer necessary.

- Operate switch for wiper/washer system until Windshield Washer Pump (V5) has delivered fluid for approximately 2 seconds.

- Read the display with the air quality sensor (G238) measured value and the recirculating/fresh air flap position => vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.

• Specification: Request for "Recirculating Air Mode" due to washer/wiper system, A/C system switches for approximately 10 seconds to the air recirculating mode.

- Wait briefly.

- Read the display with the air quality sensor (G238) measured value and the recirculating/fresh air flap position => vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.

• Specification: no request for "Recirculating Air Mode" present, A/C system in fresh air or partial recirculating air mode.

• Depending on the composition of the windshield washer fluid, the Air Quality Sensor (G238) can determine impurities in the air and request for "Automatic air recirculation".

• If no changeover to recirculating air mode occurs when operating switch for windshield wiper/washer system, check function (the information "Wash Windshield" is received via Comfort CAN-Bus system) => Vehicle Diagnosis, Testing and Information System VAS 5051 in the "Guided Fault Finding" function.

If the function of Air Quality Sensor (G238) is OK for this test and there is a customer complaint continue as follows:

- Check dust and pollen filter for dirt => [ Dust and Pollen Filter ] Dust and Pollen Filter.

- Close the Vehicle Diagnosis, Testing and Information System (VAS 5051) and select the "Read Measured Value Block" function => Vehicle Diagnosis, Testing and Information System VAS 5051.

- Second person is required to read out values displayed whilst driving.

- Follow the safety instructions => vehicle diagnosis, testing and information system VAS 5051.

- Select the display group with the measured values for the Air Quality Sensor (G238) and for the recirculating/fresh air door position => Vehicle Diagnosis, Testing and Information System VAS 5051.

- Start by driving vehicle into an area with a relatively clean atmosphere (A/C system is working in fresh-air mode).

- Then drive vehicle into an area where the atmosphere is polluted (e.g. onto an uphill road with lorry traffic).

- Read the display with the measured value for the Air Quality Sensor (G238) and for the recirculating/fresh air door position. The display must change, for example when driving through a diesel gas cloud (e.g. from fresh air mode to "Automatic Air Recirculation") => Vehicle Diagnosis, Testing and Information System VAS 5051.

- Also read and heed descriptions => [ Dust and Pollen Filter ] Dust and Pollen Filter and => [ Air Quality Sensor Function ] Description and Operation.
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