Hello,

I am attempting to reset trip fuel from a PV350 display. This display is communicating with a Cummin's CM850 ECU.

I am currently reading PGN 65257 SPN 182 (Listed as Trip Fuel, which is displaying correctly). I am attempting to reset the value contained in this PGN/SPN by sending a 1 to the engine ECU (for 5 seconds) via PGN 56832 SPN 988 (Trip Group 1) when a button is pressed. I can confirm that this message is indeed being broadcast as I have CANCapture plugged into the CANbus.

When I look up the description for this PGN/SPN I get.

"Command signal used to reset the PGNs and parameters as defined in Table SPN988 A.

00 Take no action
01 Reset"

So my question to you is am I displaying the incorrect Trip Fuel PGN/SPN for this reset action to apply, or am I not sending the right PGN/SPN to the engine ECU to force a clearing action?

I realize this is not entirely a display related question, but I am running out of ideas to try. Any insight you may have into this would be extremely helpful.

Show us a few complete 29bit packets you're XMIT'ing demonstrating your source address, priority, how you're populating the ancillary SPNs on that PGN, and the timebase/repetition rate.

IE:
MSG T(ms) Rx/Tx ID(hex) Len. 1 2 3 4 5 6 7 8
874) 4240.9 Rx 18FFA000 8 0 0 FF FF FF FF 1 A0
875) 4241.5 Rx 18FFC000 8 0 0C 0 0 FE FF 0 C0

The first question is really should be, "What does the Cummins documentation state?". Not always do the engine manufacturers use standard SPNs for everything. It is possible that they are using another SPN (possibly proprietary) for the reset function. It should be clearly identified in the documentation.

Assuming that you are using the correct SPN, several manufacturer's ECUs require seeing the transition from 0 to 1. This means that you cannot just send a 1, or send it a 1 after a 11 ("don't care"), as it must see the transition from 0 to 1. Again, this should be detailed in the documentation.

Good point, if the documentation covers such advanced topics. Caveat: taking any engineering document for gospel, especially one pertaining to software behavior, is equally dangerous as ignorance.

Hopefully the CM850 does not reflect my experiences with the industrial/high horsepower Quantum series, >30Liter. The documentation (AEB 15.43) is full of good intentions and bad information. Its utility should be limited to populating SPN descriptions with Cummins' language in place of generic SAE descriptions. The bulk of It is neither accurate, nor complete, and covers none of the nuanced request-response details you allude to. There are many omissions, deviations, and even significant differences between J1939 behaviour of engines within the same family. The situation they created requires a document drafted for each individual engine serial number, and what they supply is a compilation of errata dating back to 2004 with only minor revisions since. Firsthand testing is the only way to discover how any given Cummins ECM operates with reasonable certainty.

Alb, mbowdich,

I ended up doing some testing. The Cummin's AEB was not correct, regarding the parameter I was supposed to be sending it.

The issue has been since resolved and there's another happy, yet small, OEM company using PV's out there now.