2006 Outback Wagon - 250k miles never any engine or electrical issues. Power wash engine compartment after routine oil change. Upon completion backed out of bay; She started then stalled with an "Er HC" Code in a strange place... ABOVE the Odometer. Hasn't been able to start since (6 months). Hooked up Computer; it would not come on. Bought new computer; same thing. My mechanic has gone through ever connection attached to top wire harness and nothing. Ideas????

That display is an indication of a failure in the CAN High circuit. Probably the gauge cluster isn't able to communicate with the ECM or BCM on CAN H. You will need an oscilloscope to troubleshoot the CANBUS lines. Could be a wiring issue or more likely one of the modules is shorted or open on the CAN H and pulling the signal up/down or causing it to float due to a termination circuit failure. 

https://support.squarell.com/index.php?/Knowledgebase/Article/View/94/0/can-high--can-low

Replacing the computer requires reprogramming the immobilizer - which is synced between the ECM, Body Module (BCM), the gauge cluster, and the chip key. 

This is very involved level of diagnostics that many shops are not equipped for. Even many dealers have no one on staff that is capable of diagnosing this. You will need to find someone in your area that is familiar with CANBUS diagnostics AND the proclivities of Subaru's. 

GD

 

Edited September 26, 20214 yr by GeneralDisorder

Search Uncle Google for ErHC

among many postings I came across this one with a "SOLVED"

 

Edited September 26, 20214 yr by brus brother