Checking Control Function

& Component Testing >> Engine Sensors & Switches >> Heated Oxygen Sensor >> Checking Control Function Checking Control Function Select "READING MEASURING VALUE BLOCK" function 08 on (VAG 1551) Scan Tool and input display group 01. See CONNECTING SCAN TOOL (VAG 1551). NOTE: A display value OVER 1.04 indicates that the HO2S has detected a lean condition and, to compensate, has enriched the control system. A display value UNDER 0.96 indicates that the HO2S sensor has detected enrichment and to compensate, has created a lean condition. Observe display value in channel 3. Display must be: 0.96-1.04 volts. Display must not remain at 1.0 volts (average value): value must fluctuate. If specified value is NOT obtained, check for the following malfunctions: Fuel system pressure too high or too low. See FUEL PRESSURE under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. Leak in intake air system between engine and Mass Air Flow (MAF) sensor. Inspect for vacuum leaks. Leak in exhaust system between engine and HO2S probe. Inspect for exhaust leaks. Fig 1: Identifying Location Of HO2S Signal Control Harness Connectors [IMAGE: http://127.0.0.1:8080/images25/G00149776/] Courtesy of AUDI OF AMERICA, INC.