CAN C Bus Where is the other 120 Resistor
I am trying to find the culprit in High Speed CAN Bus. Bus Resistance is 120 Ohm and that resistance is in the PCM. Can anyone tell me what module is supposed to have the other 120 Ohm resistor. Steering column Module or Gear Shift Module or TIPM (Front Control Module) or ….
Thanks for any help.
It will be in the front control module
Yes. I was impatiently looking. I blame it on old age.
I did a little searching and turned up this. I highlighted the important part in paragraph 3 OPERATION The Controller Area Network (CAN) data bus allows all electronic modules or nodes connected to the bus to share information with each other. Regardless of whether a message originates from a module on the lower speed CAN-B bus or on the higher speed CAN-C or CAN-D bus, the message structure…
Ronald, Jeremy and Bob have supplied you with all the information you need about the system. May I ask where you are taking your measurements, though? Are you taking it at pin 6 and 14 of the data link connector? Or are you taking a measurement with the FCM gateway unplugged and measuring downstream from the FCM (pins 8&9)? If you are measuring downstream with the FCM disconnected then…
Thanks for info. Yes I was measuring at pin 8 and 9 on FCM unplugged and was getting 120 ohm and then when I unplugged PCM I was getting infinite resistance but when I plugged FCM back in and measured from PCM I was still getting an infinite resistance and that was what made me decide to ask about where the other 120 ohm was. When I was doing this I still had the battery connected so I…
Is the fault, while driving, the same as the fault shown in the ACCy mode? Is the bias shift in ACCy always there? Can you post a picture of the CAN C bus layout?
I don't think I get faults in the ACCy mode. I believe there are no faults until the bus intermittently cuts out while driving. I should really check if it faults in ACCy mode though. The bias shift is always there in ACCy mode. Here is the CAN C layout. diag.net/file/f4duty5ix…
The bias shift in ACCy is likely not a fault. It is a strategy of the bus being turned off. I would disregard it and get a capture of when the fault is occurring. Comparing the layout of the bus connections to the NO Comm complaints didn’t give a direction due to the ring type layout. Although S104 and S105 do give convenient access to isolate the modules except for the SCM and shift lever…
No codes set in ACCy mode. Thanks I will disregard the bias shift and try and record failure while driving again. Out of shop until Monday but will try again then.
120 ohm resistors are in PCM and TIPM (FCM) as many told me. Ultimately road testing until the bus started to act up eventually led me to a problem with the CAN bus in the PCM. My CAN Diagnostics post has more info on my diagnostic endeavors. Thanks for all your help.