Climate Control Exhaust Gas Sensor: Testing and Inspection
Air Quality Sensor (G238), Checking
Special tools, testers and auxiliary items required
• Vehicle diagnosis, testing and information system (VAS5051B) with diagnostic cable (VAS 5051/5A)
• Commercial Gas Lighter
Test Prerequisites
• Vehicle standing in a clean atmosphere (away from running engines, exhaust vents, etc.).
• Engine compartment and plenum chamber clean (not contaminated with oil or fuel).
• Engine compartment and plenum chamber not sprayed with cleaning agents or preservatives containing solvents.
Checking
- With ignition switched off, connect Vehicle diagnosis, testing and information system (VAS 5051B) with diagnostic cable (VAS 5051/5A) to the Data Link Connector of vehicle.
- Start the engine.
- Check DTC memory of Climatronic Control Module (J255) using Vehicle diagnosis, testing and information system (VAS5051B) in "Guided Fault Finding" function.
- Set operating mode "Auto" on Climatronic Control Module.
- Switch on "automatic air recirculation" function on Climatronic Control Module.
- Wait 30 seconds for the air quality sensor to warm up.
- Using the Vehicle diagnosis, testing and information system (VAS 5051B) select "read measured values block". Refer to Vehicle diagnosis, testing and information system (VAS5051B) in "Guided Fault Finding" function.
- Read the air quality sensor measured values.
• The operating condition of the fresh/recirculation air door and the condition of the signal from the air quality sensor is displayed in the measured values block. Refer to Vehicle diagnosis, testing and information system (VAS5051B) in "Guided Fault Finding" function.
• Specified value: no request for "Recirculating air mode" present, (A/C system in fresh air mode)
or
• Specified value: no request for "automatic recirculation mode" present, request for "partial recirculation mode" present (fresh air/recirculating door in the center position)
- Remove the air quality sensor from the mount. Refer to=> [ Air Quality Sensor (G238) ] Service and Repair.
- Allow a little bit of gas from the lighter flow past - B - from the top area - A - of the air quality sensor.
• There are different versions of the air quality sensor, each with different functions. Make sure the allocation is correct. Refer to Electronic Parts Catalog (ETKA).
• If the Air Quality Sensor (G238) comes in contact with cigarette smoke or with gas from an ignitor, it will react since ignitor gas is heavier than air; remove the air quality sensor.
- Read the display.
• Specified value: (request for "Automatic air recirculation" present, request is fulfilled, A/C switches to recirculating air mode)
- Wait a short period time (approximately 1 minute, depending on amount of test gas sprayed on Air Quality Sensor (G238) ).
- Read the display.
• Specified value (no request for "Recirculating air mode" present, air conditioning in fresh air mode)
or
• Specified value: no request for "automatic recirculating air mode", request for partial recirculating air mode.
• In order to avoid frequent shifting of the fresh/recirculating air doors, the requirement of the Air Quality Sensor (G238) sensor 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.
- Operate switch for wiper/washer system until Windshield Washer Pump (V5) has delivered fluid for approximately 2 seconds.
- Read the display.
• Specified value: Request for "Recirculating Air Mode" due to washer/wiper system, A/C system switches for approximately 10 seconds to the air recirculating mode.
- Wait briefly.
- Read the display.
• Specified value (no request for "Recirculating air mode" present, air conditioning in fresh air mode)
or
• Specified value: no request for "automatic recirculating air mode", partial recirculating air mode active
• Depending on the composition of the windshield washer fluid, the Air Quality Sensor (G238) can determine impurities in the air and request for "Automatic air recirculation".
• If no change-over to the recirculation air mode occurs when the operating switch for the windshield wiper/washer system, check the function (the information "wash windshield" is received via the databus system comfort from the steering column electronic control module (J527) ). Check using Vehicle diagnosis, testing and information system (VAS5051B) in "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 dust and pollen filter for dirt. Refer to=> [ Dust and Pollen Filter ] Service and Repair.
- Connect fault read-out device and select the "Guided Fault Finding " using Vehicle diagnosis, testing and information system (VAS5051B) in "Guided Fault Finding" function.
- Second person is required to read out values displayed whilst driving.
- Follow the safety instructions using Vehicle diagnosis, testing and information system (VAS5051B) in "Guided Fault Finding" function.
- Read the air quality sensor measured value using Vehicle diagnosis, testing and information system (VAS5051B) in "Guided Fault Finding" function.
- Start by driving 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 (e.g. onto an uphill road with lorry traffic).
- Read the displays in the display fields. The display in the display fields must change; for example, when driving through a Diesel exhaust cloud. Check using Vehicle diagnosis, testing and information system (VAS5051B) in "Guided Fault Finding" function.
- Also read and heed descriptions => [ Dust and Pollen Filter with Activated Charcoal Insert ] Description and Operation and => [ Air Quality Sensor (G238) ] Description and Operation.