Climate Control Exhaust Gas Sensor: Testing and Inspection
Sensor For Air Quality -G238-, Checking
Special tools and equipment
- VAS 5051 Vehicle Diagnostic, Testing and Information System with diagnostic cable VAS 5051/1
- Test gas D 007 855 A2
Test requirements:
- Vehicle is in area where there is clean recirculating air (not near running engines, openings from exhaust systems, etc.)
- Engine compartment and plenum chamber are clean (not contaminated with oil and/or fuel).
- The engine compartment and plenum chamber were not sprayed with cleaning or preservative solutions.
Checking
- With ignition switched off, connect VAS 5051 Vehicle Diagnostic, Testing and Information System with diagnostic cable VAS 5051/1 to 16-pin diagnostic connector on vehicle. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks" under "Heating and Air Conditioning", Testing and Inspection
- Start engine.
- Check DTC Memory
- Select "Auto" operating mode on A/C Control Head -E87-.
- Press button -A- for "Automatic air recirculation" (LED in -A- button comes on).
- Wait 30 seconds (warm up time of sensor for air quality -G238-).
Indicated on display of VAS 5051:
- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08.
- Remove plenum cover.
Indicated on display of VAS 5051:
- Display field -1- indicates request to input display group.
- Display field -2- shows input keyboard.
- Input via keyboard in display field 2 the desired display group umber "015" (See overview of selectable display groups). Refer to Scan Tool Testing/Measuring Value Blocks (Function 08)" under "Heating and Air Conditioning", Testing and Inspection
- Confirm input using the -Q- button.
- Check indications shown in display fields -1- and -2-
NOTE: Display field -1- shows the operating conditions of fresh air/recirculation flap and display field -2- indicates the condition of the air quality sensor signal. Clarification of possible displays. Refer to Scan Tool Testing/Measuring Value Blocks (Function 08)/Display Group 015" under "Heating and Air Conditioning", Testing and Inspection
- Specified value in display field -1-: 00 or 0
(no request for "air recirculation mode", climate control in fresh air mode)
or
- Specified value in display field -1-: 60
("Partial air recirculation mode", the fresh air/recirculation flap is so positioned that approx. 1/3 air is sucked in from the passenger compartment)
- Place spray head -A- of test bottle over air inlet of sensor for air quality -B-.
- Activate spray head -C- of test bottle for 1 second.
NOTE:
- The content of the test bottle consists of pure oxygen with a specified amount of nitrogen oxide.
- If the sensor comes in contact with cigarette smoke or gas from a lighter it will react.
- Read value indicated in display field -1-.
- Specification: 10
(request for "Automatic air recirculation" available, requirement is fulfilled, A/C switches to air recirculating mode)
- Wait a short period time (approx. 1 minute, depending on amount of test gas sprayed in sensor).
- Read value indicated in display field -1-.
- Specification: 00 or 0
(no request for "air recirculation mode", climate control in fresh air mode)
or
- Specification: 60 (Partial air recirculation mode)
NOTE: In order to avoid quick shifting from the recirculating air/fresh air flap, the requirement from the sensor for "Automatic air recirculation" mode is at least 25 seconds (minimum duration period), especially if the pollutant concentration has been reduced considerably so that recirculating air mode is no longer necessary.
- Operate switch for wiper/washer system until windshield washer pump -V5- has been cycled for approx. 2 seconds.
- Read value indicated in display field -1-.
- Specification: 30
(Requirement for recirculating air due to washer/wiper system, A/C switches for approx. 15 seconds to the air recirculating mode)
- Wait a short period time.
- Read value indicated in display field -1-.
- Specification: 00 or 0
(no request for "air recirculation mode", climate control in fresh air mode)
or
- Specification: 60 (Partial air recirculation mode)
NOTE:
- Depending on the composition of the windshield washer fluid, the sensor can determine impurities in the air and request for "Automatic air recirculation".
- If when activating the wiper/washer system the mode does not switch over to recirculating air, check the wiring connection between A/C Control Head -E87- and Wiped Washer Intermittent Relay -J31- (the information "windshield washing" is send via a separate wiring connection to A/C Control Head -E87-) (Read measuring value block display group 017). Refer to Scan Tool Testing/Measuring Value Blocks (Function 08)/Display Group 017" under "Heating and Air Conditioning", Testing and Inspection
If the functions of the Sensor for air quality - G238- is OK for this test and there is a customer complaint continue as follows:
- Check dust and pollen filter for dirt.
- Connect VAS 5051 and select "Read measuring value block" function 08.
- A second technician is required because the indicated values must be read out in the vehicle interior.
- Observe safety caution notes.
- Enter display group number "015".
- Drive vehicle to area with relatively clean ambient air (system operates in fresh air mode).
- Now drive vehicle into an area with heavily polluted ambient air (e.g. on a street construction or truck traffic).
- Check indications shown in display fields -1- and -2- Display fields -1- and -2- must change when driving through a diesel exhaust cloud. Meaning: See Read measuring value block display group 015 (See overview of display groups). Refer to Scan Tool Testing/Measuring Value Blocks (Function 08)" under "Heating and Air Conditioning", Testing and Inspection