Originally Posted by
red_2005_convertible
To quickly check if it's not a broken wire in the CAN BUS, you could measure the resistance between pins 11 and 4 on connector C4 of the ECU (I might be wrong on the connector number, but you can check it in the service manual). With the car off, key out of the ignition, it should read roughly 60 ohms. If it reads 120 ohms, you probably have a CAN BUS wiring problem. Hopefully, it's just as simple as a bad RCM.
Good Luck,
-Jerry
PS. sometimes with a CAN BUS error, it will throw codes saying that it can't communicate with the HVAC module.
Hi Jerry,
I was curious if the CAN BUS had just the single in put to the PTCM that you mentioned or perhaps there where more on other connectors, so I checked the 2008 Service manual this morning. Turns out the CAN BUS is connected to the PTCM at just that one location on connector C4. So measuring the resistance of just that one connector tells the story quickly as to CAN BUS integrity; very good thing to know. 60 ohms give or take a little is good. The CAN BUS runs to a number of splices on different circuits but they all find there way to the PTCM via just those two pins. However, correct me if I'm wrong because I did not open the car and actually check the wiring at C4, but the 2008 service manual shows pin #1 as + and pin #11 as - CAN BUS vice the pins you mentioned.
Thanks for posting that info. It is very helpful.