Please explain AIR1 J1939 message.

[jani12]

Consider a commercial truck. The Electronic Brake Systems (EBS) ECU receives following message from some other ECU. Please explain this message. From where does some other module acquire the Suspect Parameters Number (SPNs) to send to EBS ECU. What does EBS do with the SPNs it receives?

 

[jani12]

What functions of the commercial truck do these SPNs control?

 

[rjenkinsgb]

The first six appear to be literal pressure values from pressure transducers in various parts of the system.
The last one has just two data bits so four possible states. That could be eg. something like Off, Idle, Running, Faulted.

Overall I'd expect them to be compared to the expected ranges for each sensor and control warning or fault messages, plus enabling or inhibiting different brake system modes.