The MIL Status page reports whether the check engine light is on/off, and (as long as the datapoint is supported by the vehicle) will be able to tell you one or more of the following:
- Number of warm ups since DTCs cleared
The number of times since codes were last cleared that the following is detected:
- Coolant temperature rises a minimum of 20°C / 40°F after the engine is started
- Coolant temperature reaches a minimum of 70°C / 160°F (60°C / 140°F for diesels)
- Distance traveled since DTCs cleared
The total driving distance recorded by the vehicle since codes were last cleared or the battery was disconnected
- Engine run time since DTCs cleared
The total engine hours since codes were last cleared.
Note that this is engine run time, not total elapsed hours so for example codes may have been cleared two months ago but if the vehicle was driven five hours per week then this value will display 40 hours as opposed to 1,440 hours.
If the vehicle does not support the above datapoints you can use the smog check feature to check for indications of codes being recently cleared.
When codes are cleared all vehicle emissions tests are reset and will display a status of 'not complete'. In order to update the test status the vehicle must be driven under different conditions (town, highway, etc) so that the ECM may gather sufficient data to determine whether the tests have passed or failed.
If multiple tests under 'smog check' are listed as 'not complete' this may be an indication that codes have recently been cleared.