It's normal for the hoses to get pressurized. The cap isn't designed to release pressure until it hits around 15psi. As far as the code, it is a knock sensor code. However, there could be something causing it other than a bad sensor. The following would need checked:
Sensor
Sensor wiring short or open
Sensor connection for corrosion causing weak connection
ECM
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Monday, April 13th, 2015 AT 5:24 AM