Humidity Sensor: Service and Repair
Air Quality Sensor (G238)/Humidity Sensor in Fresh Air Intake Duct (G657)
• There are different versions depending on the vehicle date of manufacture and which A/C system ("Basis" or "Comfort") is installed. Refer to => [ Air Quality Sensor (G238) and Humidity Sensor in Fresh Air Intake Duct (G657) Function ] Description and Operation.
• The air quality sensor is installed only on vehicles with the "Comfort" A/C system.
• The humidity sensor in fresh air intake duct is only installed on MY 12 vehicles as a running change. Refer to => [ Air Quality Sensor (G238) and Humidity Sensor in Fresh Air Intake Duct (G657) Function ] Description and Operation.
• The air quality sensor / humidity sensor in fresh air intake duct are highly sensitive electronic components that can get damaged if they come in direct contact with solvents, fuels or chemicals (e.g. impurities may enter through area - A -). Therefore, never install an air quality sensor / humidity sensor in fresh air intake duct that was stored, for example, in a tool box.
• Following removal, do not set down air quality sensor / humidity sensor in fresh air intake duct in areas where it could come into contact with solvents, fuels or certain chemical compounds (liquids or vapors).
• There are different versions of the air quality sensor / humidity sensor in fresh air intake duct with different functions. Refer to the Parts Catalog.
Installed on high voltage systems (hybrid vehicles)
Read and follow all of the supplemental warnings for all work performed on vehicles with the high voltage system.
If it is necessary for the following procedure to perform work in the vicinity of high voltage components, perform a visual inspection of the high voltage components and cables for damages.
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.
How to handle high voltage cable:
• 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.
• Color-code the round high voltage connector with an external color ring and code them mechanically using the guide- or code tabs. Always make certain that the coding matches when connecting the round connector in order to avoid mechanically damaging 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 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 the cover 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 the plenum chamber cover - B - (there are different versions).
• Inspect the high voltage components - D - (the electric drive power and control electronics (JX1) ) and the high voltage cables - E - after removing the plenum chamber cover - B -. Refer to => [ Visual Inspection of High-Voltage Components and Cables for Damage ] Visual Inspection of High-Voltage Components and Cables For Damage.
• Be careful not to damage any high voltage components - D - or the high voltage cables - E -.
• Inspect the high voltage components - D - and high voltage cables - E - after completing the work procedure and before installing the plenum chamber cover - B -.
For vehicles without a high voltage system
- Switch off ignition.
- Pull the left rubber seal - B - as far as necessary.
- Remove the fresh air intake cover on the wind cowl - A - or the wind cowl (different styles).
• If necessary, carefully loosen the wind cowl from the windshield cross member - C -
All vehicles
- Turn the air quality sensor / humidity sensor in fresh air intake duct - A - approximately 90° to the left and remove it from the fresh air intake - C -.
- Disconnect the connector - B - from the air quality sensor / humidity sensor in fresh air intake duct.
Terminal assignment in connector - B -
1 B+ (terminal "15")
2 Ground (terminal "31")
3 Signal wire to the Vehicle Electrical System Control Module (J519).
• The signal from the air quality sensor / humidity sensor in fresh air intake duct cannot be monitored by workshop equipment.
• The vehicle electrical system control module evaluates the data from the air quality sensor / humidity sensor in fresh air intake duct and then transmits it to the Climatronic control module (J255) display and control unit via the Data bus.
• There are different versions of the air intake shroud for the fresh air intake - C - (with and without a mount for the for the air quality sensor / humidity sensor in fresh air intake duct - A -, in the front or on the side). Refer to the Parts Catalog.
• The measured values from the air quality sensor / humidity sensor in fresh air intake duct are displayed in the Climatronic control module display and control head measured values block and in the vehicle electrical system control module (J519) measured values block. Explanatory notes of the displays refer to the Vehicle Diagnostic Tester in "Guided Fault Finding" function.