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Bear with me, this is a long post, but I've been troubleshooting a bizarre intermittent transmission slipping issue and potentially a related electrical issue. Any thoughts/theories would really help here. Just to note, the two shops, Shop A and Transmission Shop B have a reasonable reputation in my area. Vehicle: 2004 Silverado LS 1500 4x4 Ext Cab Short Bed, 111,000 miles (daily driver until 2016), 3,000 miles/year since then. Owned since new, this truck has not lived a super hard life. Symptoms: 1) Initially had intermittent slipping in 1st gear, either in DRIVE or manual gear selection in middle of June 2) Continued to slip intermittently after transmission fluid/filter replaced July 6th 3) Check engine light (code P0758 ONLY) appeared late August, would not go into 4th in DRIVE and slipping in 1st gear again (in both DRIVE or manually selected). 3rd gear on highway works fine. Manual selection of 2nd and 3rd seems to be okay to get around. 4) Solenoids A and B replaced by Transmission Shop B on Sept 3rd 5) No obvious power drains EXCEPT on the IPC/DIC circuit which was about 200 milliamps 6) Previous battery draw issue over the previous 2 years. Usually would kill a battery between 12 and 48 hours. Very intermittent issue. 7) Recent wet day battery draw issue reappeared. Actions taken so far: 1) Fluid and filter replaced by Shop A on July 6th a. Worked for one week, slipping issue reappeared intermittently throughout August 2) Solenoids A and B replaced by Transmission Shop B on Sept 3rd and solenoids tested with independent power source, functioning properly. a. No change, Check Engine Light still illuminated with code P0758 3) Checked all fused circuits on Sept 4th a. One drain on the IPC/DIC circuit of about 200 milliamps Working theories (in levels of severity): 1) Possible gauge assembly short due to the IPC/DIC circuit drain possibly related to a transmission control circuit? Seen this pop up a few times on other forums, but I am doubtful, then again, this was early 00's GM where fog light fuses did not match with the fog light circuits... 2) Short on the transmission harness 3) Short between the PCM/ECU unit in the engine bay and the transmission harness 4) Bad PCM/ECU unit <-- This is my top theory considering the connectors are oriented sideways and have dirt/debris all over, combined with a wet day may result in a small short causing both the transmission issue AND the battery draw.