I have a 2004 Suburban 1500 LT with the 5.3L Vortex engine. Whenever I go through the automatic carwash, the kind that goes around the car and sprays high pressure water, my engine will start a random misfire and the check engine light will come on. The misfire will last only a few minutes or until whatever got wet gets dried out. I have a code reader but when I connect to the DLC it won't communicate with the ECU. My DLC has only 4 wires (no CAN) and when I test the pins with KOEO, no 16 has B+, no 4 has good chassis ground and no 5 has signal ground, but when I test no 2 it has less than 1 volt and fluctuates wildly. I realize that I should be getting 5 to 7v. I have tested around the coil packs by spraying a mist of water on each one with the engine running and wasn't able to detect a misfire, so I don't think one is cracked but I don't know what else it could be. Any ideas?