Funky Can Network
good morning all I have a vehicle here that is really eating at me. customer states brake light and awd light came on. then the tach and speedo stopped working. confirmed his concerns. cleared these codes and they come right back on immediately . when you start the vehicle the tach works for about ten seconds before going back to zero. I can communicate with all modules currently. I scope the network by back probing at abs module and have found the can high to be at 3.5 volts flat line and low to be at 1.5 flat line. both at what seems to be resting voltage. there is absolutely no fluctuations in these voltages. I have tried unplugging every module with the exception of the pcm and nothing changes. with the voltage on the network where they are it does not seems as if there are any shorts to ground or power. for some reason there is just no data being communicated on the network. has any one seen anything like this or have any direction for me? any help would be greatly appreciated! thank you
Check the stop lamp bulbs. It is possible to install a lamp with one washing.
Im sorry, your response is confusing. Could you elaborate on this?
Is the CAN bus flat lined as the tach is working? I believe that your scanner is communicating on the K line, so that is how you are communicating. Maybe try disconnecting the PCM and see if activity returns at the abs module?
yes, the diagnostics are communicating through the k line. I did not check to see if can bus had activity during that few seconds but I will now. and I will also try the pcm. will replay back in a few minutes thanks
Unplugging pcm did not wake up my can signal. There is no can signal when tach works for those few seconds.
So all modules on network unplugged I would check KOEO voltages on C H and C L , should be 0V if all modules off the network, then key off and add one module at a time. I had a logic lock situation (totally different vehicle) and doing it this way was able to find the bad one , and make sure that I had all modules off the network.
I’ll try that today and get back to you. Thank you
Have you disconnected the radio and/or cluster?
Is this actually a 2005? According to the wiring diagrams an 05 Acura RL with a 3.5 doesnt have a high speed CAN network at pins 6 an 14??!! Someone correct me if I am wrong but I have scoured OE and color diagrams and there is no high speed CAN.
I am sorry disregard my post. Wow the diagram is hard to understand lol. My fault.
How many modules are on this vehicle because I only show 4 with the imformation I have available to me.
Okay thanks you all for the help. The diagram I was looking at was Missing one module. That module was the navigation DVD player in the trunk deck. I unplugged this module and my network came to life. Checked power and grounds. Tested good. Vehicle has a bad nav DVD player that was making the network flat line. thank you all for the help