I recently needed to tow my cargo trailer with my 2003 Envoy. This is the first time towing with this vehicle since owning my truck. I connected to the factory connector with 7 pin to flat 4 pin adapter. The right tail lamp on the trailer had a faint glow after being plugged in to the tow vehicle. When I checked the trailer light for right turn both the right and left lights started blinking. I tried the left turn indicator and it was fine. I drover my trailer setup to a Uhaul and was told my problem was the trailer wiring. I returned home and checked the entire trailer wiring and found no shorts or other issues. I directed my attention back to my vehicle. My turn signals on the Envoy worked fine, left, right and four way. I then read about 2003 2004 Envoys had a turn signal recall for the Envoy signal system. No mention regarding any trailer issues caused by the vehicle electrical system. I change the signal module under the dash below the steering wheel anyway. This cured my turn signal issues when my trailer was connected. I made a report to the DOT regarding this issue as to the dangerous issue when towing. The recall of the signal module should extend to towing a trailer. I suspect many rarely connected their Envoy to a trailer and turn signal issue never got reported enough to create a recall. I ordered my replacement module with trailering feature from amazon. The module replacement was an easy fix and made for safe towing any trailer.