Climate Control Exhaust Gas Sensor: Testing and Inspection
Sensor For Air Quality -G238-, Checking
Test requirements
- Vehicle is in an 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 plenum chamber were not sprayed with cleaning or preservative solutions
Preparation
- Check DTC memory.
If a DTC is recognized, repair and eliminate all malfunctions.
- Remove plenum chamber cover.
Checking
- Switch ignition on.
- Set A/C control head -E87- to "Auto" operating mode.
- Start engine (compressor on).
- Press button for "Automatic air recirculation" (lamp in -A- button comes on).
- Wait 30 seconds (warm-up time of sensor for air quality -G238-).
- Connect VAG1551 Scan Tool (ST) to 16-pin Data Link Connector (DLC) using VAG1551/3 adapter cable.
- Start engine.
The on board diagnostic function for A/C control head -E87- begins (address word "08").
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08.
Indicated on display
Rapid data transfer Q
08 - Read Measuring Value Block
- Press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block
Input display group number XXX
- Input display group number "01" (overview).
- Press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block 1 ->
1 2 3 4
NOTE:
Read Measuring Value Block 1 ->
0 12.5 V 12.5 V 00
- Display "0" in display field 1 shows the compressor switched on (there is no compressor cut-off condition).
- Table of possible displays in display field 1.
- The voltage for the A/C clutch -N25- is displayed in display field 2 (e.g. 12.5 V).
- Display field 3 shows the voltage to terminal 15 (e.g. 12.5 V).
- Display field 4 shows operating condition of the fresh/recirculating air. Table of possible displays in display field 4.
- Read display from display field 4.
Read Measuring Value Block 1 ->
0 12.5 V 12.5 V 00
Specified values: "00" (no requirement for "recirculating air", A/C in fresh air mode with fresh air operation ) or "60" ("Partial recirculating air," fresh air and recirculating air flap open)
- Place spray head -A- of test bottle over air inlet of sensor for air quality -B-.
- Activate spray head -C- of test bottle for 1 second.
- The content of the test gas bottle consists of pure oxygen with a specified amount of nitrogen oxide.
- The test gas for the air quality sensor is obtained as a replacement part under the number D007 855 A2.
- If the sensor comes in contact with cigarette smoke or gas from a lighter it will react.
CAUTION!
Part numbers are listed here for reference only. Always check with your Parts department for the latest in formation.
- Read display from display field 4.
Read Measuring Value Block 1 ->
0 12.5 V 12.5 V 10
Specified value: "10" (requirement for "Automatic air recirculation" available, requirement is fulfilled, A/C switches to recirculating air mode)
- Wait a short period of time (approx. 1 minute, depending on amount of test gas sprayed in sensor).
- Read display field 4.
Read Measuring Value Block 1 ->
0 12.5 V 12.5 V 00
Specified value: "00" (no requirement for "Recirculating air," A/C system in fresh air mode or "60" (partial recirculating air)
In order to avoid quick shifting from the recirculating aid fresh air flap, the requirement from the sensor for "Automatic air recirculation mode" is at least 25 seconds (minimum duration period) especially if the pollutant concentration has been reduced considerably so that recirculating air mode is no longer necessary.
- Operate switch for wiper/washer system until windshield washer pump -V5- has been cycled for approx. 2 seconds.
- Read display from display field.
Read Measuring Value Block 1 ->
0 12.5 V 12.5 V 30
Specified value: "30" (requirement for recirculating air due to washer/wiper system, A/C switches for approx. 10 seconds to the recirculating air mode)
- Wait a short period of time.
- Read display from display field 4.
Read Measuring Value Block 1 ->
0 12.5 V 12.5 V 00
Specified Values: "00" (no requirement for "recirculating air, A/C in fresh air mode) or "60" (partial recirculating mode)
Depending on the composition of the windshield washer fluid, the sensor can determine impurities in the air and request for "Automatic air recirculation."
If when activating the wiped washer system the mode does not switch over to recirculating air, check the wiring connection between A/C control head -E87- and wiped washer intermittent relay -J31- according to the wiring diagram.
- Press -> button.
Indicated on display
Rapid data transfer HELP
Select function XX
- Push buttons -0- and -6- to select "End Output" function 06.
Indicated on display
Rapid data transfer Q
06 - End Output
- Press -Q- button to confirm input.
Indicated on display
Rapid data transfer HELP
Insert address word XX
- Switch ignition off and disconnect Data Link Connector (DLC).
If the function 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.
- Close DTC unit and select "Read Measuring Value Block" function 08.
- Drive vehicle to area with relatively clean recirculating air (the system works in fresh air mode).
- Now drive vehicle into an area with heavily polluted recirculating air (e.g. on a street with construction or and truck traffic).
Display field 4, display group 001 must change from 00 or 60 to 10 when driving through a diesel exhaust cloud.