Air Quality Sensor -G238-, CHECKING
Different versions depending on the vehicle date of manufacture and A/C system version ("Basis" or "Convenience"). Refer to Air Quality Sensor -G238-, FUNCTION .
The Air Quality Sensor -G238- is only installed on vehicles with the "Convenience" A/C system.
The Air Quality Sensor -G238- and the Humidity Sensor in Fresh Air intake Duct -G657- need approximately two minutes until they reach their operating temperature after turning on the ignition. The function of the Air Quality Sensor -G238- and the Humidity Sensor in Fresh Air intake Duct -G657- is limited during the warm-up phase.
During the warm-up phase, the Air Quality Sensor -G238- malfunctions may occur under certain ambient influences. Only replace the Air Quality Sensor -G238- if the Air Quality Sensor -G238- is repeatedly appearing as faulty. If the malfunction indicator for the Air Quality Sensor -G238- changes from "static" to "sporadic" after switching the ignition off and then on again (waiting at least two minutes each time), then the Air Quality Sensor -G238- is OK and the DTC memory entry no longer needs to be monitored (erase the DTC memory) using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
Special Tools and Equipment
- Vehicle Diagnostic Tester with the Vehicle Diagnosis System - Updated Cable - 3m VAS5051/5A
- Commercially available gas lighter (for checking the Air Quality Sensor -G238-)
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.
It is possible to switch the "automatic recirculating air mode" on or off via the "A/C System" in the "Car" menu in the MMI (Multi Media Interface). Refer to the Infotainment/MMI Operating Instructions.
Air Quality Sensor -G238-, checking function
On vehicles with a high voltage system (hybrid vehicles)
Observe all of the additional warnings for all work performed on vehicles with the high voltage system. Refer to HIGH VOLTAGE VEHICLES SAFETY PRECAUTIONS and HIGH VOLTAGE SYSTEM GENERAL WARNINGS .
If it is necessary for the following procedure to perform work near high voltage components, "perform a visual inspection of the high voltage components and cables for damages" (refer to PERFORMING A VISUAL INSPECTION OF DAMAGE TO HIGH VOLTAGE COMPONENTS AND CABLES ) and "always follow the warnings when working on the high voltage system". Refer to HIGH VOLTAGE SYSTEM GENERAL WARNINGS .
Risk of unintended engine start
The ignition must be turned off and the ignition key must remain outside of the vehicle when working on vehicles with a high voltage system.
Handling high voltage cables:
- Do not stand on or place tools on high voltage cables and their components as it may damage the cable insulation.
- Never bend or kink high voltage cables forcefully as it may damage the cable insulation.
- The round high voltage connectors are color coded with an external color ring and are mechanically coded using the guide- or code tabs. Always make certain that the coding matches when connecting the round connector in order to avoid any mechanical damage the high voltage connector.
There is a risk of electrocution from damaged high voltage components.
Observe the following when working around high voltage components and high voltage wires:
- Never work around high voltage components and cables with cutting, deformed, or sharp edged tools, or heat sources such as welding or soldering tools, heated air, and thermal glue.
- Inspect the high voltage components visually before beginning.
- Perform a visual inspection of the Electric Drive Power and Control Electronics -JX1-, the Electro-Drive Drive Motor -V141-, the Electrical A/C Compressor -V470- and the high voltage lines when working in the engine compartment.
- Perform a visual inspection of the high voltage lines and covers when working on the underbody.
- Perform a visual inspection of the high voltage lines and the Electrobox with the High Voltage System Maintenance Connector -TW- when working in the luggage compartment.
- Perform a visual inspection on all of the potential equalization cables.
Observe the following items when performing the visual inspection:
- The components do not display any signs of external damage.
- The high voltage cable insulation and the potential equalization cables are not damaged.
- The high voltage cables do not display any abnormal deformations.
- Every high voltage component is marked with a red warning label.
-- Turn off the ignition.
-- Remove the rubber seal -A- and plenum chamber cover -B- (different versions). Refer to PLENUM CHAMBER COVER, REMOVING AND INSTALLING .
- Visually inspect the high voltage components -D- (here the Electric Drive Power and Control Electronics -JX1-) and the high voltage cables -E- after removing the plenum chamber cover -B-. Refer to PERFORMING A VISUAL INSPECTION OF DAMAGE TO HIGH VOLTAGE COMPONENTS AND CABLES and HIGH VOLTAGE SYSTEM GENERAL WARNINGS .
- Be careful not to damage any high voltage components -D- or the high voltage cables -E-. Refer to HIGH VOLTAGE SYSTEM GENERAL WARNINGS .
- Visually inspect the high voltage components -D- and high voltage cables -E- after completing the work procedures and before installing the plenum chamber cover -B-. Refer to HIGH VOLTAGE SYSTEM GENERAL WARNINGS .
Working on a high voltage system when activated or with the ignition turned on
The engine may start unexpectedly when performing work while the ignition is turned on or when the ready mode is activated and may cause poisoning in enclosed spaces. Be aware of body limbs and/or clothing when clamping or pulling.
Perform the following steps before turning on the ignition:
- Move the selector lever into position P.
- Activate the parking brake.
- Switch off ignition.
- Open the engine hood.
- Connect the charging unit for example Battery Charger VAS5903 to the battery jump start terminal for the 12V vehicle electrical system
- Switch on the ignition.
-- Charge the vehicle battery, for example, using the Battery Charger VAS5903 in the battery support mode to minimize the number of automatic starts during the test- and measuring procedures when the ready mode is active. Refer to Battery Charger VAS5900 SUPPORT MODE and HIGH VOLTAGE SYSTEM GENERAL WARNINGS .
-- Move the selector level into position "P", activate the parking brake and arrange the necessary tools for testing and measuring procedures that require the ready mode to be active or that require the ignition to be on, so that they cannot come into contact with the turning components in the engine and so that they are not in the vicinity of the turning components of a running engine.
Also move the selector lever into position "P" and activate the parking brake for testing and measuring procedures which require the ignition to be on, but do not require the ready mode to be active.
The ready mode is displayed in the Instrument Cluster Control Module -J285- above the "power meter". Refer to Owner's Manual.
Activate and deactivate the ready mode. Refer to Owner's Manual (consult the display in the Instrument Cluster Control Module -J285-).
For vehicles without a high voltage system
-- Turn off the ignition.
-- Pull off the rubber seal -B- on the left side as far as necessary. Refer to PLENUM CHAMBER COVER, REMOVING AND INSTALLING .
-- Remove the cover for the fresh air intake on the cowl panel trim -A- or the cowl panel trim (different versions). Refer to PLENUM CHAMBER COVER, REMOVING AND INSTALLING .
If necessary, carefully loosen the cowl panel trim from the retainer on the windshield cross member -C-. Refer to PLENUM CHAMBER COVER, REMOVING AND INSTALLING .
All vehicles
-- With the ignition switched off, connect the Vehicle Diagnostic Tester with the Vehicle Diagnosis System - Updated Cable - 3m VAS5051/5A to the vehicle diagnostic connection and initiate the Guided Fault Finding using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
-- Turn on the ignition (vehicles with the high voltage system).
-- Start the engine (vehicles without the high voltage system).
The vehicle electrical system may turn off the engine on a vehicle with the Start/Stop System.
-- Check the DTC memory for the Climatronic Control Module -J255- display and control head using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
-- Set the "Auto" mode on the Climatronic Control Module -J255- display and control head ("Convenience" version).
-- Via the MMI (Multi Media Interface), set the "automatic recirculating air mode" on the Climatronic Control Module -J255- display and control head. Refer to Infotainment/MMI Operating Instructions.
-- Wait two minutes. (warm-up time for the Air Quality Sensor -G238-).
-- Via the Vehicle Diagnostic Tester, select the "read measured values block" function and then read the measured values for the Air Quality Sensor -G238- using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
The NOx- portion (nitrogen oxide) and the CO- portion (carbon monoxide) in the air measured by the Air Quality Sensor -G238- is displayed in the measured values block. For an explanation for possible displays using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function
-- Turn the Air Quality Sensor -G238- -A- approximately 90° to the left and remove it from the fresh air intake -C-.
-- Allow a little bit of gas from a lighter -B- to flow past from the top area -A- of the Air Quality Sensor -G238-.
If the Air Quality Sensor -G238- comes in contact with cigarette smoke or with gas from a lighter, it will react since butane gas is heavier than air; therefore, remove the Air Quality Sensor -G238-.
-- Select and read the measured value block with the Air Quality Sensor -G238- measured values using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
Specified values:
- The measured values increase contrary to the initial value in the display fields and show that both sensors in the Air Quality Sensor -G238- are working correctly and the Air Quality Sensor -G238- electronics are evaluating the measured values properly.
-- Wait a short period of time (approximately one minute, depending on amount of test gas flowing into the sensor).
-- Read the Air Quality Sensor -G238- measured values.
Specified values:
- The measured values will return to the output values and by doing so, show that both sensors are working correctly, and that the sensor electronics evaluated the measured values correctly.
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 values:
- The display field will show that the A/C is working in the fresh air mode.
If a deviating value from the "fresh air mode" is displayed in the measured values block, then there is already a request for recirculating air mode (for example, due to the request for "maximum cooling output" or "manual recirculating air mode)". Select a setting that does not require recirculating air mode.
If is appears in the measured values block that the Air Quality Sensor -G238- is already requesting automatic recirculating air mode, then, if necessary, clean the plenum chamber or move the vehicle into an area where the surrounding air is cleaner using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function
-- Allow a little bit of gas from a lighter -B- to flow past from the top area -A- of the Air Quality Sensor -G238-.
-- Read the recirculation/fresh air mode display.
Specified values:
- In the measured values block, it will be displayed that a request for air recirculation is present and that the A/C system is working in the air recirculation mode.
If is shows in the measured values block that the Air Quality Sensor -G238- has requested automatic recirculating air mode, this request will not be performed based on a Shut-Off condition from the Climatronic Control Module -J255- display and control head. Repair the cause for this Shut-Off condition, if necessary using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function
In order to avoid frequent shifting of the recirculated air/fresh air doors and the recirculation doors, the requirement of the Air Quality Sensor -G238- for "Automatic air recirculation" mode remains for at least 25 seconds (minimum duration period), even if the pollutant concentration is so far reduced that recirculated air mode is no longer necessary.
-- Wait a short period of time (approximately one minute, depending on amount of test gas flowing into the sensor).
- If the measured value block shows that there is no longer a request for air recirculation, then the A/C system is working again in the fresh air mode.
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 DUST AND POLLEN FILTER, REMOVING AND INSTALLING .
-- With the ignition switched off, connect the Vehicle Diagnostic Tester with the Vehicle Diagnosis System - Updated Cable - 3m VAS5051/5A to the vehicle diagnostic connection and using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
-- Using the Vehicle Diagnostic Tester, select the "Read measured values block" function using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
A second person is required to read out the values displayed while driving.
Always pay attention to the safety instructions using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function
-- Read the displays in the measured values block for the Air Quality Sensor -G238- measured values and the recirculation/fresh air mode request.
-- Drive the vehicle into an area with a relatively clean atmosphere (system in fresh-air mode).
-- Then drive vehicle into an area where the atmosphere 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.
Also pay attention to the descriptions. Refer to DUST AND POLLEN FILTER, REMOVING AND INSTALLING (Dust and Pollen Filter, Removing and Installing) and Air Quality Sensor -G238-, FUNCTION .