MC43 Errors in logs after key off

Larri 6 years ago in Master modules / MC4x updated 6 years ago 3

We noticed that we are getting the errors below in the MC43 log occasionally and it appears to get logged when turning machine off.  Machine runs fine and no errors appear during running.  I verified that the log has no errors during running, but when I key off and then key on and check MC43 log, the errors below are logged in MC43 log.


Any ideas as to why these errors would get logged on key off intermittently?  Any suggestions as to resolve this?


Satisfaction mark by Larri 6 years ago

It is hard to say after just seeing the channel names, but it seems as if some that get status Error are DOUT channels (pin type and type of loads are relevant to know here), and the ones that get Critical error might be VIN (fuel level and hyd pressure normally are). The one that is more clear is the VREF error. 

What I would guess is that you have something unusual going on with the supply voltage at key off, my recommendation would be to start by taking some scope measurements on MC43 supply voltage in this installation. 


I saw a system log from a different machine with mix of similar symptoms; where it most probably originated from the 12V system dropping unusually low during cranking. 

To give some more details on this question; it is possible to see VREF error and CAN bus error / No contact if the module supply voltage drops extremely low without falling below the level where the module switch off. Specifically on the MC4x and MC4xFS, the added I/O diagnostics (e.g. checking of AD converters) can trigger VIN critical error status and COUT/DOUT error status. In bench-testing I have seen that by dropping supply voltage to ~5.7 V, it is possible to provoke all these symptoms.

There is logging of +BAT low supply, this is logging when supply is <9V, but the reason this is not seen here is that it has has a relatively long 2.5 s delay-on time to avoid logging during normal cranking. 

Compared to the supply voltage, the delay time for I/O and VREF errors is very short, these diagnostic tests are designed to react very quickly -between system cycle time and a 100 ms.  That is why these are the statuses that can get written to the log. 

In this particular case, when the error gets logged at key-off, I think that something in the electrical installation is causing the supply voltage to drop unusually slow. Maybe other electronic controllers with large capacitors on their supply voltage. 

If you simply want to mask the logging of events related to under-voltage, one trick could be to use an IDC to disable the system log when the MDGN +BAT is below a certain level, say < 7 V. 

For some more details on output channel statuses, also see: 



Thanks for the info and looking into this issue!