Test Group TBM2.8VJGKEK
Secondary Air System Monitoring General Description - At cold start, secondary air pump and valve are switched on for their normal operating function. Secondary air delivered into exhaust gas is causing a lean mixture indicated by output voltage of oxygen sensor. Any time the oxygen sensor indicates a lean mixture within the maximum time for monitoring, a counter is incriminated by "one" up to a predetermined value. This fixed limit corresponds to the minimum amount of secondary air (low-flow-limit-check). For secondary air system monitoring flow chart, see Fig 1.
Conditions For Enabling Diagnosis - The diagnosis is performed only if the secondary air pump is switched on. The sampling of measured values (rate =: 20 ms.) will be started if the following conditions are met for at least .7 seconds:
- Oxygen sensor is heated up (stabilized conditions).
- Cold start enrichment activated.
- Coolant temperature greater than 50°F (10°C) and less than 158°F (70°C).
- For criteria for high altitude driving conditions, see Fig 2.