The most frequently-reported failure mode of the ESS is internal cracking of the housing, allowing oil UNDER the VC to enter the ESS housing, and to collect in the sockets. Inspect the ESS Sockets (as opposed to the seal around the periphery of the ESS) for any oil INSIDE the sockets. I would suggest 'Unlocking' the Connector to the ESS and Disconnecting the Connector. However, even IF the oil film or seepage your photos show is from the gasket, THAT would NOT cause the two ESS Signal Fault Codes you list in my opinion. The primary concern is NOT to crack the plastic VC when removing OLD Seal or inserting NEW.
Any proper-sized Seal Driver or even large socket will work instead of 'Special Tool'. Three ISTA ScreenPrints of Repair Operation are attached.
Click to expand.The gasket IS easy to replace (WITHOUT removing VC).
