| Hello Xrele
I've ordered a diagnostic cable, eBay item 271314999189 (KKL-VAGCOM Adapter), model taken from the compatibility list of MultiEcuScan Software available online on their website. In the meanwhile I'm checking all the wiring, especially ones coming from the outside temperature sensor and from doors: usually they suffer from strain as they are moved a lot in car life. Outside temperature sensor is situated near the left foglight on the front bumper, below the radiator line (in order to avoid interference in measurements from the heat radiated) and it is also subject to dirt, bumps, hits and soaking.
As you may already know, car onboard units all speak can-bus protocol that is (from the PHY viewpoint) a two wire protocol on a balanced line. If one of the two wires loosens from the junction connectors or looses its insulation coating, communication is lost for all units in the bus (as the share the same cable). First of all check connections in the junction box below the steering wheel, paying attention not to loosen or remove connectors from other units (in that box you'll find a lot of connectors from ECM, ABS, ESP and many more). Check the fuse box, especially ones marked as BCM (see workshop manual) situated inside the fuse box (that is just below bcm and junction box under the steering wheel). Using the workshop manual (follow strictly the procedure), and a multimeter, check if the unit is correctly powered and receiving signals from sensor. Do not put multimeter on signal cables (ones marked as CAN in the manual) or on cables not related to our unit (always double check before touching with multimeter leads any pin, there are airbag arming signals, too). If you're arrived reading here, I think you're already a technician or entusiast and all my "warnings" are not useful, I know.
When the connector and I will be both home, I'll do the DTC check and clearance, to find the faulty unit (a cable for sure). I'm sure the BCM disables itself after a number of communication failures and then reenables again, after a fixed number of system restarts (this is why I think my BCM sometimes comes back alive).
I think I'll work on the car on next saturday cause now I'm out for work. Stay tuned, I'll update this post. Comments, suggestions and anything else can improve my (our) knowledge about our systems are always welcome.
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