99 Tahoe Rough Idle with DTC 171 and 1133 - Troubleshooting Guide

Jeff, after over six years of moderating automotive forums, I've learned that no matter how clearly we explain technical issues, some users struggle with reading, communication, or expressing appreciation. This is a common challenge in both repair shops and online communities—especially when people are trying to save money on repairs. I’ve seen firsthand how frustration can build quickly if solutions don’t work the first time, such as registration issues or unexpected site behavior. While these situations are unavoidable, they highlight the importance of clear, accurate technical communication. This post focuses specifically on a 1999 Tahoe experiencing rough idle, with diagnostic trouble codes (DTC) 171 and 1136. These codes point to potential issues in the engine control system and fuel delivery—common problems in older GM trucks. Proper diagnosis involves checking the throttle position sensor, fuel pressure, and ignition timing. Always verify code accuracy using an OBD-II scanner before proceeding with repairs.