Technical Fiat Ducato 2015 Can Bus B

[NZGrahamO]

Hi All

I have a 2015 Fiat Ducato.

I think I have a problem on Can Bus B with is the low speed can bus.
With a ODB2 break out box both Can Bus C high speed bus and Can Bus B low speed bus show they are working o/k with key turned on.
Using Multiecuscan I can read all the modules in the van on both C and B can bus with key turned on.
Checking proxi alignment all modules show up o/k with key turned on.

When I check for terminating resistor on C can bus with the power disconnected I read 65 ohms which is within range.
Checked on pin 6 and 14 on ODB2 terminal.
When I check for terminating resistor on B can bus with power disconnected I have open circuit. No ohm reading.
Checked on pin 1 and 9 on ODB2 terminal.

When the key is turned off I get 11 volts on ( B can bus ) pin 9 of the ODB2 terminal.

Question is.
Does pin 9 ( B can bus ) on the ODB2 with key turned off normal for it to show 11 volts.
E.g Does pin 9 ( B can bus ) not go into sleep mode
Is there a terminating resistor on the low speed B can bus.
If so where is it.

Thank You
Graham O

 

[bugsymike]

Although very old school I am interested in the operation of the Can Bus system and use a breakout box occasionally, so a big learning curve.
I found on this site :-https://www.vwvortex.com/threads/pin-1-of-obd-connector.5026085/ it mentions that pin 1 is supplied with battery voltage only with ignition on, would that account for "open circuit?" with ignition off?
If safe to do so would it be possible to check for the terminating resister Ohm reading between Can L and earth, rather than completing the circuit through OBD 1.
After over 50 years in the motortrade and now retired I still find it interesting, but things like Can Bus systems and their even more advanced later versions I find, shall we say challenging

 

[NZGrahamO]

Although very old school I am interested in the operation of the Can Bus system and use a breakout box occasionally, so a big learning curve.
I found on this site :-https://www.vwvortex.com/threads/pin-1-of-obd-connector.5026085/ it mentions that pin 1 is supplied with battery voltage only with ignition on, would that account for "open circuit?" with ignition off?
If safe to do so would it be possible to check for the terminating resister Ohm reading between Can L and earth, rather than completing the circuit through OBD 1.
After over 50 years in the motortrade and now retired I still find it interesting, but things like Can Bus systems and their even more advanced later versions I find, shall we say challenging

Thanks for your reply.
Your info refers to a different way of pin out on the ODB2.
Fiat use pin 16 on the ODB2 as the 12 volt positive output. and pins 4 and 5 as the 12 volt negative output.
Pin 1 and 9 are used for Can Bus B high / low.
I have tested with power off pin 1 and pin 9 to ground.
Both tests show open circuit which means the Can B is not shorted to ground.

Thank You
Graham O