cfauvel wrote: ↑
Mon Jan 16, 2023 10:23 am
Yes I DO have an idea, and you are NOT going to like it.
It is an issue with your high speed CAN bus, the network of your car.
You have one of these issues somewhere on your network.
CAN HIGH shorted to ground
CAN LOW shorted to ground
CAN HIGH shorted to pos
CAN LOW shorted to pos
Both wires shorted together
or resistive short on either wire to ground, POS or to themselves
or intermittent OPEN on these wires.
Now for the crappiness.....WHERE?!?!
I am new to learning about the CAN bus and other bus system in the car, BUT from what I've learned dealing with my G35 and 350z is that there are few components to keep in mind and where they are.
The buses in the car ALL have to get combined into a GATEWAY, and it is NOT the ECM. On our cars the GATEWAY is the Unified Control Module (90% sure of what I am saying) and that lives on the instrument cluster. Surprisingly enough the wiring diagram shows the UCM being connected to the A/C control module and also surprisingly doesn't control JUST the A/C (I don't recall ALL that it controls).
I've read here that replacing the A/C control module fixes stuff on the front of the instrument cluster, like lights, fuel gauge level, but am highly suspect of that. But THAT being said a used A/C control module is cheap on ebay and junk yards so MAYBE worth taking a look.
Do you go through car washes regularly? My G35 does and have narrowed down my issue (about 90% sure) to being some short in or around the transmission wire loom for the TCM , as I have similar issues and worse as you about an hour after going through the car wash. My car is in the shop :-) Hopefully the guy is good at finding CAN bus issues.
try to keep tabs as to WHEN it happens. Such as only on first startup of the day after sitting for several hours, every time you startup.
Maybe look up where all the modules are located and disconnect /reconnect each one that is easily accessed. In doing so you might get lucky and be just a loose connection between a pin and its connector, or you might SEE a bad wire.
I don't know the colors for the CAN bus wires...BUT they will be 2 wires that are twisted together. I believe ONLY network wires (CAN, LIN, etc) are twisted pair.