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Home >> Audi >> 2003 >> A4 Cabriolet (8H7) L4-1.8L Turbo (AMB) >> Repair and Diagnosis >> Sensors and Switches >> Sensors and Switches - HVAC >> Climate Control Exhaust Gas Sensor >> Testing and Inspection >> Sensor For Air Quality -G238-, Checking

Sensor For Air Quality -G238-, Checking




Sensor For Air Quality -G238-, Checking

Special tools and equipment
- VAS 5051 Vehicle Diagnostic, Testing and Information System with VAS 5051/1 diagnostic cable
- Test gas bottle D 007 855 A2

Test requirements:
- Vehicle is in area where there is clean recirculating air (not near running engines, openings from exhaust systems, etc.)
- Engine compartment and plenum chamber are clean (not contaminated with oil and/or fuel).
- The engine compartment and fresh air plenum chamber were not sprayed with cleaning or preservative solutions.

Checking
- With ignition switched off connect VAS 5051 Vehicle Diagnostic, Testing and Information System with VAS 5051/1 diagnostic cable to 16-pin data link connector on vehicle. Connecting VAS 5051 Tester
- Start engine.
- Check DTC memory.
- Select "Auto" operating mode on A/C Control Head -E87-.







- The button for "Automatic recirculated air" -A- is activated (lamp in -A- button comes on).
- Wait 30 seconds (warm up time of sensor for air quality -G238-).

Indicated on display of VAS 5051:







- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08.
- Remove plenum cover.

Indicated on display of VAS 5051:







- Display field -1- indicates request to input display group.
- Display field -2- shows input keyboard.

- Input via keyboard in display field 2 the desired display group umber "014" (see overview of selectable display group numbers). Measuring Value Blocks (Function 08)
- Press -Q-button to confirm input.
- Read indications shown in display fields -3- and -4-.

NOTE:
- Display field -4- shows the operating conditions of fresh air/recirculated flap and display field -3- shows the condition of the air quality sensor signal. Table of possible displays. Display Group 014
- Specified value in display field -4-: 00 (no request for "Recirculated air mode", air conditioning in fresh air mode)
or
- Specified value in display field -4-: 60 ("Partial recirculated air mode", fresh air and recirculated air flap open)







- Place spray head -A- of test gas bottle over air inlet of sensor for air quality -B- (with version "1").
- Place spray head -A- of test gas bottle over air inlet of sensor for air quality -B- (with version "2").
- Press spray head -C- of test gas bottle for 1 second.

NOTE:
- The content of the test bottle consists of pure oxygen with a specified amount of nitrogen oxide.
- The sensor for air quality is in different housings, version "1" was installed at beginning of production. This sensor was replaced in a running change to version "2", however it has the same function.
- If the sensor comes in contact with cigarette smoke or gas from a lighter (gas is heavier than air, therefore remove and rotate sensor) it will react.

- Read value indicated in display field -4-.
- Specification: 10: (request for "Automatic recirculated air" mode present, request is fulfilled, A/C changes to recirculated air mode)
- Wait a short period time (approx. 1 minute, depending on amount of test gas sprayed in sensor).
- Read value indicated in display field -4-.
- Specification: 00: (no request for "Recirculated air mode", air conditioning in fresh air mode)
or
- Specification: 60 (Partial recirculated air mode)

NOTE: In order to avoid frequent shifting of the recirculated air/fresh air flap, the request from the sensor for "Automatic recirculated air" mode remains for at least 25 seconds (minimum duration period), even if the pollutant concentration in the air is so far reduced, that recirculated air mode would be no longer necessary.

- Operate switch for wiper/washer system until windshield washer pump -V5- delivered washer fluid for approx. 2 seconds.
- Read value indicated in display field -4-.
- Specification: 30: (Request for "Recirculated air" mode due to washer/wiper system, A/C switches for approx. 10 seconds to the recirculated air mode)
- Wait a short period time.
- Read value indicated in display field -4-.
- Specification: 00: (no request for "Recirculated air mode", air conditioning in fresh air mode)
or
- Specification: 60 (Partial recirculated air mode)

NOTE:
- Depending on the composition of the windshield washer fluid, the sensor can determine impurities in the air and request for "Automatic air recirculation".
- When activating the wiper/washer system and the system does not change-over to recirculated air mode, check function of Wiper/Washer Intermittent Relay -J31- (the information "windshield washing" is received from the Steering Column Electronic Systems Control Module -J527- via the CAN-bus comfort system ) (See Read Measuring Value Block, display group 018).
- If the functions of the Sensor for air quality -G238- is OK for this test and there is a customer complaint continue as follows:
- Check dust and pollen filter for dirt.
- Connect VAS 5051 and select "Read measuring value block" function 08.
- A second technician is required because the indicated values must be read out in the vehicle interior.
- Enter display group number "014".
- Drive vehicle to area with relatively clean ambient air (system operates in fresh air mode).
- Now drive vehicle into an area with heavily polluted recirculated air (e.g. on a street construction or truck traffic).
- Read indications shown in display fields -3- and -4-. Display fields -3- and -4- must change when driving through a diesel exhaust cloud (meaning: see Read Measuring Value Block display group 014). Measuring Value Blocks (Function 08)
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