Removing and installing air quality sensor G238 with humidity sender in fresh air intake duct G657 — AUDI

Removing and installing
air quality sensor
G238
with
humidity sender in fresh air intake duct
G657
Note
There are different versions of
G238
/
G657
A
. Attention is therefore to be paid to correct assignment
Electronic parts catalogue
.
G238
(with
G657
) is only fitted on a vehicle with a
“High”
air conditioner
Electronic parts catalogue
.
A vehicle with a
“High”
air conditioner is fitted with a sensor
A
on which
G238
C
is combined with
G657
D
in one component
Electronic parts catalogue
and
Audi sales range
.
A vehicle with a
“Low”
air conditioner (or no air conditioner, heater only) only has a sensor
A
with
G657
D
but with no
G238
C
Electronic parts catalogue
and
Audi sales range
There are different versions of the fresh air intake depending on the vehicle model
Electronic parts catalogue
. The fitting location of
G238
(with
G657
)
A
also differs depending on the version of the fresh air intake
Chapter
“
Removing and installing fresh air intake
”
. This and the following illustrations show
G238
(with
G657
)
A
for a fresh air intake of the type fitted at the start of production.
The sensor
A
(combined sensor comprised of
G238
and
G657
) is a highly sensitive electronic component which could be irreparably damaged by direct exposure to fluids, solvents, fuels and certain chemical compounds (contamination may ingress e.g. via area
C
or
D
). In addition, direct contact with water can impair the function of
G657
to such an extent that the values for humidity levels can can no longer be measured correctly (either temporarily or permanently, depending on the composition of the fluid). Sensors that have come into contact with such substances must not be installed in the vehicle.
Following removal, do not set down
G238
/
G657
in areas where it could come into contact with solvents, fuels or certain chemical compounds (liquids or vapours).
Removing
Switch off the ignition.
Detach the plenum chamber cover
F
from the vehicle at the front right and carefully raise slightly
General body repairs, exterior
Rep. gr.
50
Bulkhead; Removing and installing plenum chamber cover
.
Give
G238
/
G657
A
an approx. 90° turn and remove it from the mount at the fresh air intake
E
.
Unplug electrical connector
B
from sensor
A
.
Note
The signal emitted by
G238
and
G657
cannot be evaluated using workshop equipment.
The data of
G238
and
G657
are evaluated by
E87
Vehicle diagnostic tester
“Guided fault-finding”
mode and
Current flow diagrams, Electrical fault finding and Fitting locations
.
The measured values of
G238
and
G657
are displayed in the
“Reading measured values”
function of the guided fault-finding routine for
E87
. For explanatory notes on displays, refer to
Vehicle diagnostic tester
“Guided fault-finding”
mode.
Installing
Install in reverse order, paying attention to the following:
Note
The plenum chamber cover
A
and the outer cover (drip rail)
C
must be intact to stop water running into the heater and air conditioning unit via the intake box
B
with the plenum chamber cover
A
fitted. The plenum chamber cover
A
must also be properly and fully engaged in the lower windscreen frame
D
.
The intake grille must be intact (check) to stop foreign matter (e.g. leaves) ingressing into the intake box
B
.
Depending on the model, a dust filter may be fitted in the filter mount instead of the grille for certain countries with a high dust impact level in the ambient air (e.g. for China). This dust filter stops dust and sand being drawn in by the
fresh air blower
V2
. For assignment, refer to
Electronic parts catalogue
.
Following installation, interrogate the event memory of the
front air conditioner operating and display unit
E87
and erase any faults displayed
Vehicle diagnostic tester
“Guided fault-finding”
mode.