Audi Q7: Air Quality Sensor -G238- Function
Function of Air Quality Sensor -G238-
Note
- There are different versions of the Air Quality Sensor
-G238-/ humidity sensor in Fresh Air Intake Duct -G657--A-.
Therefore, ensure the correct allocation. Refer to the Parts
Catalog.
- Depending on the vehicle version, there are different fresh
air intake versions. Refer to the Parts Catalog. Depending on
the version of the fresh air intake the component location of
the Air Quality Sensor -G238--C-
(with the humidity sensor in Fresh Air Intake Duct -G657--D-)
is different. Refer to
→ Chapter "Fresh Air Intake, Removing and Installing".
This and the following illustrations show the Air Quality Sensor
-G238--C- (with the Humidity Sensor
in Fresh Air Intake Duct -G657--D-)
for a fresh air intake version "1".
- On a vehicle with a "Mix" of "High" A/C system a sensor
-A- is installed in which the Air
Quality Sensor -G238--C- with the
Humidity Sensor in Fresh Air Intake Duct -G657--D-
are combined in a single component. Refer to the Parts Catalog
and the Audi Sales Program.
- On a vehicle with a "Low" or "Mid" A/C system only a sensor
-A- with a Humidity Sensor in Fresh
Air Intake Duct -G657--D- but
without an Air Quality Sensor -G238--C-
is installed. Refer to the Parts Catalog and the Audi Sales
Program.
- The Air Quality Sensor -G238--C-
uses a sensor to determine the NOx level (nitrogen oxide) and CO
level (carbon monoxide) in the air flowing by and exchanges this
information with the Front A/C Display Control Head -E87- via a
local data bus. Therefore, ensure the proper version and
allocation of the Air Quality Sensor -G238- / humidity sensor in
Fresh Air Intake Duct -G657-. Refer to the Parts Catalog.
- The measured value of the Air Quality Sensor -G238--C-
is evaluated by the Front A/C Display Control Head -E87-. Upon
request, the Front A/C Display Control Head -E87- switches to
recirculating air mode if no shut-off condition is present.
Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding"
function.
- Certain A/C system functions (for example, control of
automatic recirculation mode) can be switched on and off via the
MMI (Multi Media Interface) under the "A/C system" function in
the "car"/"vehicle" menu. The A/C system control can also be
influenced via the presets in the MMI (Multi Media Interface)
under the "A/C system" function in the "Car"/"Vehicle" menu.
Therefore, check the preset in the MMI first in the case there
is a problem with these components. Refer to Infotainment/MMI
Operating Instructions.
- The Air Quality Sensor -G238--C-
requires approximately 30 seconds to reach its operating
temperature after the ignition is switched on. During the
warm-up phase, the function of the Air Quality Sensor -G238- is
limited.
- The Air Quality Sensor -G238--C-
detects pollutants in the surrounding air (usually gasoline
and/or diesel exhaust) and causes the Front A/C Display Control
Head -E87- to switch the A/C system to recirculation mode.
The Front A/C Display Control Head -E87- identifies the type
and intensity of the air pollutant by the signal from the Air
Quality Sensor -G238-. Moreover, the Front A/C Display Control
Head -E87- receives the sensitivity set by the Multimedia System
Control Head -E380- via the data bus. Based on this information,
the Front A/C Display Control Head -E87- then determines if and
when the A/C system switches to recirculating air mode. Refer to
the Infotainment/MMI Operating Instructions and use the Vehicle
Diagnostic Tester in the "Guided Fault Finding" function.
Example:
- At an outside temperature above approximately +2 ºC (35.6
ºF), the recirculation mode is switched on upon request from the
Air Quality Sensor -G238- when there is only a slight increase
in the pollutants in the ambient air.
- If the outside air temperature goes below -1ºC (30.2 ºF) and
"ECON mode" is activated (the A/C compressor is switched off and
the indicator lamp in the A/C Max or
A/C button is off), the switch-over
takes place first when there is a significant increase in the
pollutant concentration and only for approx. 15 seconds. If
there is another increase in the pollutant concentration within
approximately two minutes, the Front A/C Display Control Head
-E87- does not switch to "recirculation mode" at this time.
- If the A/C compressor is switched off ("ECON" mode is on and
the indicator lamp in the A/C Max or
A/C button is off), the maximum
duration of the "automatic recirculation mode" is limited to 15
seconds by the Front A/C Display Control Head -E87- (so that the
windshield, rear window, and door windows do not fog up).
- If the concentration decreases, the A/C system switches to
the fresh air mode.
- The duration of "automatic recirculating air mode" depends
on the version of the Front A/C Display Control Head -E87- and
the setting on the Multimedia System Control Head -E380-. If the
outside air temperature is below +10 ºC (50 ºF) and the maximum
sensitivity on the Multimedia System Control Head -E380- is
reached, the system will stay on for approximately 30 seconds in
"automatic recirculation mode". After this, it switches back to
fresh air mode. If another increase in the pollutant
concentration occurs within approximately two minutes, the Front
A/C Display Control Head -E87- does not switch over to
"automatic recirculation mode" during this time.
- The "automatic recirculating air mode" function can be
switched off at any time. If the function is active, the A/C
compressor is switched on with a request for "automatic
recirculating air mode" and also when the exterior temperature
is below approximately +2 ºC (35.6 ºF). If the temperature is
below -5 ºC (23 ºF), then it is not possible to use the A/C
compressor.
- At setting "automatic recirculating air mode" in the MMI
(Multi Media Interface), the A/C compressor can also be switched
on when the recirculating air mode is manually switched on
(using the "recirculation button") up to a temperature of
approximately - 5ºC (23 ºF).
- To ensure that the A/C system is not constantly working in
recirculating air mode in areas with consistently high air
pollution, the Air Quality Sensor -G238- is self-adapting (it
adjusts its sensitivity to the environmental conditions).
- If the outside air pollution load remains relatively high
for a long period of time, the Air Quality Sensor -G238- starts
to adapt itself to the altered environmental conditions through
an adaptation program so that the air recirculation request is
generally shorter than 12 minutes in uniformly polluted
surrounding air. If a succession of peaks in the polluted air is
detected, the A/C system can operate over a longer period of
time in recirculating air mode.
- A certain amount of time is required for repositioning of
the A/C system doors. In the event that a sudden increase in
pollutants is encountered (for example when driving through a
diesel exhaust cloud) gaseous pollutants can be taken in with
the fresh air into the passenger compartment until the door can
be closed. For this reason, on vehicles equipped with an Air
Quality Sensor -G238- a dust and pollen filter is installed with
a charcoal layer. A filter that is saturated with pollutants is
no longer effective and needs to be replaced.
- To prevent excessive operation of the back pressure/fresh
air door and the air recirculation door, the door is not
immediately activated if there is a nominal increase in
pollutants in the surrounding air (the Air Quality Sensor -G238-
does not send a request to the Front A/C Display Control Head
-E87-). The filtering of the activated charcoal insert in the
dust and pollen filter will be sufficient.
- In order to avoid excessive operation of the back
pressure/fresh air door and the air recirculation door, a
request from the Air Quality Sensor -G238- for "automatic
recirculation mode" remains active for at least 25 seconds
(minimum duration period), even if the pollutant concentration
is so far reduced that recirculation mode is no longer
necessary.
- To defog fogged-up windshield, rear window, and door windows
as quickly as possible, the Front A/C Display Control Head -E87-
does not allow recirculation mode in the "defrost" mode (a
request from the Air Quality Sensor -G238- is not implemented).
- After the ignition is switched on, Air Quality Sensor -G238-
requires approximately 30 seconds to be operational (warm-up
time). During this time there is no request from the Air Quality
Sensor -G238- to the Front A/C Display Control Head -E87- for
the "automatic recirculating air mode".
- Sensor -A- (combination sensor
with the Air Quality Sensor -G238- and the Humidity Sensor in
Fresh Air Intake Duct -G657-) is a highly sensitive electronic
component that can be damaged if it comes in direct contact with
fluids, solvents, fuels and certain chemical compounds.
Moreover, the function of the Humidity Sensor in Fresh Air
Intake Duct -G657- can be severely affected by direct contact
with water so that correct moisture values can no longer be
measured (briefly or permanently depending on the composition of
the fluid). For this reason, do not install sensors that may
have come into contact with these substances.
- Under certain ambient influences, when switching on the
ignition (for example, when the air pollution is high), if a
fault on the Air Quality Sensor -G238- is stored in the Front
A/C Display Control Head -E87- during the Air Quality Sensor
-G238- warm-up time, even though the sensor is OK, proceed as
follows:
- Switch off the ignition for a minimum of two minutes.
- Switch on the ignition and wait at least two minutes.
- Read the DTC memory of the Front A/C Display Control Head
-E87-. If the Air Quality Sensor -G238- still displays a static
malfunction, perform Guided Fault Finding. Refer to Vehicle
Diagnostic Tester. If the Air Quality Sensor -G238- is no longer
displayed as a malfunction, or the malfunction was sporadic, the
Air Quality Sensor -G238- is OK (and does not need to be
observed). Erase the event memory.
Air Quality Sensor -G238- Functionality, Checking
Note
- There are different versions of the Air Quality Sensor
-G238-/ Humidity Sensor in Fresh Air Intake Duct -G657--A-.
Therefore, ensure the correct allocation. Refer to the Parts
Catalog.
- Depending on the vehicle version, there are different fresh
air intake versions. Refer to the Parts Catalog. Depending on
the version of the fresh air intake the component location of
the Air Quality Sensor -G238--C-
(with the Humidity Sensor in Fresh Air Intake Duct -G657--D-)
is different. Refer to
→ Chapter "Fresh Air Intake, Removing and Installing".
This and the following illustrations show the Air Quality Sensor
-G238--C- (with the Humidity Sensor
in Fresh Air Intake Duct -G657--D-)
for a fresh air intake version "1".
- On a vehicle with a "Mix" of "High" A/C system a sensor
-A- is installed in which the Air
Quality Sensor -G238--C- with the
Humidity Sensor in Fresh Air Intake Duct -G657--D-
are combined in a single component. Refer to the Parts Catalog
and the Audi Sales Program.
- On a vehicle with a "Low" or "Mid" A/C system only a sensor
-A- with a Humidity Sensor in Fresh
Air Intake Duct -G657--D- but
without an Air Quality Sensor -G238--C-
is installed. Refer to the Parts Catalog and the Audi Sales
Program.
- The Air Quality Sensor -G238--A-
requires approximately 30 seconds to reach its operating
temperature after the ignition is switched on. During the
warm-up phase, the function of the Air Quality Sensor -G238- is
limited.
- During the warm-up phase, the Air Quality Sensor -G238-
malfunctions may occur under certain ambient conditions. Only
replace the Air Quality Sensor -G238- if the Air Quality Sensor
-G238- is continually registered as faulty. If the malfunction
indicator for the Air Quality Sensor -G238- changes from
"static" to "sporadic" after switching the ignition off and back
on again (wait at least two minutes), the Air Quality Sensor
-G238- is OK and it is no longer necessary to pay attention to
the DTC memory entry (erase the DTC memory). Refer to Vehicle
Diagnostic Tester in the "Guided Fault Finding" function.
- Certain A/C system functions (for example, control of
automatic recirculation mode) can be switched on and off via the
MMI (Multi Media Interface) under the "A/C system" function in
the "car"/"vehicle" menu. The A/C system control can also be
influenced via the presets in the MMI (Multi Media Interface)
under the "A/C system" function in the "Car"/"Vehicle" menu.
Therefore, check the preset in the MMI first in the case there
is a problem with these components. Refer to Infotainment/MMI
Operating Instructions.
Special Tools and Equipment
- Vehicle diagnostic tester
Test Requirements
- Vehicle standing in a clean atmosphere (away from running
engines, exhaust vents, etc.)
- Engine compartment and the plenum chamber are clean (not
contaminated with oil or fuel)
- The engine compartment and the plenum chamber were not
sprayed with cleaning agents or preservatives containing
solvents
- "Automatic recirculating air mode" is switched on.
Note
It is possible to switch the "automatic recirculation mode"
on or off via the "A/C" function in the "car"/"vehicle" menu in
the MMI (Multi Media Interface). Refer to Infotainment/MMI
operating instructions.
Checking Function
- Remove the plenum chamber cover. Refer to
→ Body Interior; Rep. Gr.50; Bulkhead; Plenum Chamber Cover,
Removing and Installing.
Note
So that with an installed plenum chamber cover no water runs
via the outer fresh air intake box cover (rain water drain
channel) -E- in the fresh air
intake, the plenum chamber cover must not be damaged. In
addition the plenum chamber cover must be correctly and
completely engaged in the windshield frame.
- Remove the outer cover for the fresh air intake box (rain
water drain channel) -E-. Refer to
→ Chapter "Fresh Air Intake, Removing and Installing"
- Remove the Air Quality Sensor -G238- / Humidity Sensor in
Fresh Air Intake Duct -G657--A-
from the inner cover for the fresh air intake box
-F- (do not remove connector
-B-).
- Connect the Vehicle Diagnostic Tester to the data link
connector of the vehicle with the ignition switched on and
initiate the Guided Fault Finding. Refer to Vehicle Diagnostic
Tester.
- Start the engine.
- Retrieve the Front A/C Display Control Head -E87- DTC
memory. Refer to Vehicle Diagnostic Tester in the "Guided Fault
Finding" function.
- Set the "Auto" mode on the Front A/C Display Control Head
-E87-.
- Set "automatic recirculating air mode" via the MMI (Multi
Media Interface) in the Front A/C Display Control Head -E87-.
Refer to Infotainment/MMI Operating Instructions.
- Wait two minutes. (Air Quality Sensor -G238- warm-up time).
- Via the Vehicle Diagnostic Tester select the "Read the
measured values" function and read out the current status for
the fresh or recirculating air mode. Refer to Vehicle Diagnostic
Tester in the "Guided Fault Finding" function.
Note
- For an explanation of the possible displays. Refer to
Vehicle Diagnostic Tester in the "Guided Fault Finding"
function.
- The Front A/C Display Control Head -E87- calculates the
measured values of the Air Quality Sensor -G238- (for the air
pollution) and the different settings of the status for the
recirculating or fresh air mode. Refer to Vehicle Diagnostic
Tester in the "Guided Fault Finding" function.
Specified value:
- The heating and A/C system works in fresh air mode.
- Turn the Air Quality Sensor -G238--A-
approximately 90º.
- Allow a little bit of gas -B- to flow past from the top area
-A- of the Air Quality Sensor
-G238-.
- In the Guided Fault Finding function "Read the measured
values" read out the current status of the fresh or
recirculating air mode. Refer to Vehicle Diagnostic Tester in
the "Guided Fault Finding" function.
Specified Values:
- In the display fields, the measured values for the "fresh
air/recirculating air mode" change with respect to the initial
value, thus indicating that the Air Quality Sensor -G238- is
functioning properly and the Air Quality Sensor -G238-
electronics are evaluating the measured values correctly.
- The display field will show that the heating and A/C system
is working in the recirculating air mode.
Note
The sensor itself cannot be checked with service equipment
at this time, if the air composition around the sensor changes,
the signal from the Air Quality Sensor -G238- and also the
display value from the request for the fresh and recirculating
air mode status also changes. Refer to Vehicle Diagnostic Tester
in the "Guided Fault Finding" function.
- Wait a short period of time (approximately one minute,
depending on amount of test gas flowing at the sensor).
- In the Guided Fault Finding function "Read the measured
values" read out the current status of the fresh or
recirculating air mode. Refer to Vehicle Diagnostic Tester in
the "Guided Fault Finding" function.
Note
Due to changed pollution values, it is possible that
different values can be displayed than those by the first
measuring.
- Read the display with the measured values for the A/C
operating status (recirculation/fresh air operation).
Specified value:
- The display field will show that the heating and A/C system
is working in the fresh air mode.
Note
- If a value deviating from the "fresh air mode" is displayed
in the "read measured values" function of the Guided Fault
Finding, there is already a request for recirculation mode (for
example, due to the request for "maximum cooling output" or the
"manual recirculation mode" setting). Select an operating mode
that does not require recirculation mode.
- If it is displayed in the "read measured values" function of
the Guided Fault Finding that the Air Quality Sensor -G238- is
already requesting automatic recirculation mode, clean the
plenum chamber or move the vehicle into an area where the air is
cleaner. Refer to Vehicle Diagnostic Tester 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 the dust and pollen filter for soiling. Refer to
→ Chapter "Dust and Pollen Filter, Removing and Installing".
- Connect a Vehicle Diagnostic Tester to the data link
connector of the vehicle with the ignition switched on and
initiate the Guided Fault Finding. Refer to Vehicle Diagnostic
Tester.
- Via the Vehicle Diagnostic Tester, select the "read measured
values" function. Refer to Vehicle Diagnostic Tester in the
"Guided Fault Finding" function.
Note
A second technician is required to read out the displayed
values while driving.
Note Safety Information:
- Read out the displays in the "read measured values" function
of the Guided Fault Finding for the measured values of the Air
Quality Sensor -G238- and the recirculation/fresh air mode
request. Refer to Vehicle Diagnostic Tester in the "Guided Fault
Finding" function.
- Drive the vehicle into an area with a relatively clean
atmosphere (system in fresh-air mode).
- Then drive the vehicle into an area where the surrounding
air is polluted (for example, onto an uphill road with truck
traffic).
- Read the displays in the different display fields. The
displays in the different display fields must change; for
example, when driving through a diesel exhaust cloud.
Note
Pay attention to the descriptions. Refer to
→ Chapter "Dust and Pollen Filter, Removing and Installing"
and
→ Chapter "Air Quality Sensor -G238- Function"
(functionality of the Air Quality Sensor -G238- and the Humidity
Sensor In Fresh Air Intake Duct -G657-).
Humidity Sensor In Fresh Air Intake Duct -G657- Function
Note
- There are different versions of the Air Quality Sensor
-G238-/ Humidity Sensor in Fresh Air Intake Duct -G657--A-.
Therefore, ensure the correct allocation. Refer to the Parts
Catalog.
- Depending on the vehicle version, there are different fresh
air intake versions. Refer to the Parts Catalog. Depending on
the version of the fresh air intake the component location of
the Air Quality Sensor -G238--C-
(with the Humidity Sensor in Fresh Air Intake Duct -G657--D-)
is different. Refer to
→ Chapter "Fresh Air Intake, Removing and Installing".
This and the following illustrations show the Air Quality Sensor
-G238--C- (with the Humidity Sensor
in Fresh Air Intake Duct -G657--D-)
for a fresh air intake version "1".
- On a vehicle with a "Mix" of "High" A/C system a sensor
-A- is installed in which the Air
Quality Sensor -G238--C- with the
humidity sensor in Fresh Air Intake Duct -G657--D-
are combined in a single component. Refer to the Parts Catalog
and the Audi Sales Program.
- On a vehicle with a "Low" or "Mid" A/C system only a sensor
-A- with a Humidity Sensor in Fresh
Air Intake Duct -G657--D- but
without an Air Quality Sensor -G238--C-
is installed. Refer to the Parts Catalog and the Audi Sales
Program.
- The sensor of the Humidity Sensor in Fresh Air Intake Duct
-G657--D- installed in the sensor
-A- calculates the temperature and
the moisture in the air flowing by and exchanges the information
with the Front A/C Display Control Head -E87- via the local data
bus. Therefore, ensure the proper version of the Air Quality
Sensor -G238- / humidity sensor in Fresh Air Intake Duct -G657-.
Refer to the Parts Catalog.
- The measured value of the Humidity Sensor in Fresh Air
Intake Duct -G657- is evaluated by the Front A/C Display Control
Head -E87-.
- Certain A/C system functions (for example, control of
automatic recirculation mode) can be switched on and off via the
MMI (Multi Media Interface) under the "A/C system" function in
the "car"/"vehicle" menu. The A/C system control can also be
influenced via the presets in the MMI (Multi Media Interface)
under the "A/C system" function in the "Car"/"Vehicle" menu.
Therefore, check the preset in the MMI first in the case there
is a problem with these components. Refer to Infotainment/MMI
Operating Instructions.
- The Front A/C Display Control Head -E87- uses the measured
values to calculate the current relative humidity of the
drawn-in fresh air. The calculated humidity value is used to
detect whether there is a risk of the windshield, rear window,
and door windows fogging up on the inside. If that is the case,
the Front A/C Display Control Head -E87- changes various
characteristic curves to counteract this. This can be performed,
for example, by lowering the evaporator temperature (by
activating the A/C compressor), by raising the response
thresholds for the request for automatic recirculation mode, by
preventing motor shut-off via the start-stop function, etc.
Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding"
function.
- The Humidity Sensor in Fresh Air intake Duct -G657- needs
approximately 30 seconds until it has reached its operating
temperature after the ignition is switched on. During the
warm-up phase, the function of the Humidity Sensor in Fresh Air
intake Duct -G657- is limited.
- Sensor -A- (combination sensor
with the Air Quality Sensor -G238- and the Humidity Sensor in
Fresh Air Intake Duct -G657-) is a highly sensitive electronic
component that can be damaged if it comes in direct contact with
fluids, solvents, fuels and certain chemical compounds.
Moreover, the function of the humidity sensor in Fresh Air
Intake Duct -G657- can be severely affected by direct contact
with water so that correct moisture values can no longer be
measured (briefly or permanently depending on the composition of
the fluid). For this reason, do not install sensors that may
have come into contact with these substances.
Humidity Sensor in Fresh Air intake Duct -G657-, Checking
Note
- There are different versions of the Air Quality Sensor
-G238-/ Humidity Sensor in Fresh Air Intake Duct -G657--A-.
Therefore, ensure the correct allocation. Refer to the Parts
Catalog.
- Depending on the vehicle version, there are different fresh
air intake versions. Refer to the Parts Catalog. Depending on
the version of the fresh air intake the component location of
the Air Quality Sensor -G238--C-
(with the Humidity Sensor in Fresh Air Intake Duct -G657--D-)
is different. Refer to
→ Chapter "Fresh Air Intake, Removing and Installing".
This and the following illustrations show the Air Quality Sensor
-G238--C- (with the Humidity Sensor
in Fresh Air Intake Duct -G657--D-)
for a fresh air intake version "1".
- On a vehicle with a "Mix" of "High" A/C system a sensor
-A- is installed in which the Air
Quality Sensor -G238--C- with the
Humidity Sensor in Fresh Air Intake Duct -G657--D-
are combined in a single component. Refer to the Parts Catalog
and the Audi Sales Program.
- On a vehicle with a "Low" or "Mid" A/C system only a sensor
-A- with a Humidity Sensor in Fresh
Air Intake Duct -G657--D- but
without an Air Quality Sensor -G238--C-
is installed. Refer to the Parts Catalog and the Audi Sales
Program.
- The Humidity Sensor In Fresh Air Intake Duct -G657--D-
requires approximately 30 seconds to reach its operating temperature after
the ignition is switched on. During the warm-up phase, the function of the
Humidity Sensor in Fresh Air Intake Duct -G657- is limited. Refer to Vehicle
Diagnostic Tester in the "Guided Fault Finding" function.
- The function of the Humidity Sensor in Fresh Air intake Duct -G657-
can only be checked via the Guided Fault Finding. The measured values of the
Humidity Sensor in Fresh Air intake Duct -G657- are evaluated there via the
"read measured values" function and are compared to the temperature and
humidity measured at the component location of the Humidity Sensor in Fresh
Air intake Duct -G657-. Refer to Vehicle Diagnostic Tester in the "Guided
Fault Finding" function
READ NEXT:
Air Quality Sensor -G238- with the Humidity Sensor In Fresh Air Intake
Duct -G657-, Removing and Installing
Note
There are different versions of the Air Quality Sensor
-G238-/ Humidity Sen
Left Front Upper Body Vent Temperature Sensor -G385-, Removing and
Installing
Removing
- Move the driver seat as far back as possible.
- Turn off the ignition.
- Remove the driver side
Left Rear Upper Body Vent Temperature Sensor -G635-, Removing and
Installing
Note
The Left Rear Upper Body Vent Temperature Sensor -G635- is
only installed on vehicles with a "High" A/C syst
SEE MORE:
Removing
- Turn off the ignition.
- Remove the glove compartment (for the right condensation
water drain). Refer to
→ Body Interior; Rep. Gr.68; Storage Compartments and Covers;
Glove Compartment, Removing and Installing.
- Remove the driver side instrument panel c
Winter tires significantly improve the vehicle's
handling when driving in winter conditions. Because
of their construction (width, compound,
tread pattern), summer tires provide less traction
on ice and snow.
Use winter tires on all four wheels.
Only use winter tires that are approved for your
v