PIDs 0101 (monitor status since DTCs cleared) and 0141 (monitor status this drive cycle) are both returning the monitor status, however as per the specification only 0101 differentiates between spark ignition and compression ignition, hence the bit-to-monitor-mapping is different.
As per the standard documents (and Wikipedia1), this distinction is missing in 0141, so how am I supposed to interpret the result of 0141 on a compression ignition vehicle then?
All the PID details are in ISO 15031-5. You have to either buy it (arouond 80$) or find it anyhow!! Infos about PIDs are not complete (even sometimes ambiguous!) on Wikipedia. Below is some information and differences between 0x01 and 0x41 (But not complete and you cannot parse the information with it!). Hopefully helps:
0x01 is Monitor status since DTCs cleared. The bits in this PID shall report two pieces of information for each monitor:
1) monitor status since DTCs were last cleared, saved in NVRAM or Keep Alive RAM
2) monitors supported on the vehicle.
0x41: the bit in this PID shall report two pieces of information for each monitor:
1) Monitor enable status for the current driving cycle. This bit shall indicate when a monitor is disabled in a manner such that there is no easy way for the driver to operate the vehicle to allow the monitor to run.
Typical examples are
⎯ engine-off soak not long enough (e.g., cold start temperature conditions not satisfied)
⎯ monitor maximum time limit or number of attempts/aborts exceeded
The monitor shall not indicate “disabled” for operator-controlled conditions such as rpm, load, throttle position. The monitor shall not indicate “disabled” from key-on because minimum time limit has not been exceeded or engine warm-up conditions have not been met, since these conditions will eventually be met as the vehicle continues to be driven.
If the operator drives the vehicle to a different altitude or ambient air temperature conditions, monitor status may change from enabled to disabled. The monitor shall not change from disable to enable if the conditions change back. This could result in a monitor showing “disabled” but eventually showing “complete”.
2) Monitor completion status for the current driving/monitoring cycle. Status shall be reset to “not complete” upon starting a new monitoring cycle. Note that some monitoring cycles can include various engineoperating conditions; other monitoring cycles begin after the ignition key is turned off. Some status bits on a given vehicle can utilize engine-running monitoring cycles while others can utilize engine-off monitoring cycles. Resetting the bits to “not complete” upon starting the engine will accommodate most engine-running and engine-off monitoring cycles; however, manufacturers are free to define their own monitoring cycles.
In the latest version of the standard (SAE J1979DA-201406) – which I have since bought – they have clarified that bit by specifying B3 as injection bit for both 0101 and 0141. Thus this question has been solved.