1994 C4 Corvette idles rough but no OBD-II codes. Solution: Use Mode 22 to view the IAC position and TPS closed-throttle voltage. The tool reveals a TPS voltage of 0.78V (spec is 0.45-0.65V) – adjusting the TPS fixes the idle.
On your scanner, select “GM Enhanced” or “Manufacturer Specific.” Choose the PCM (engine/transmission module). gm mode 22 scan tool by terry
The GM Mode 22 scan tool is a handheld device that's designed to connect to your vehicle's OBD-II port, allowing you to access a wide range of diagnostic information and perform various tests. The tool is specifically designed for General Motors vehicles, including cars, trucks, and SUVs. 1994 C4 Corvette idles rough but no OBD-II codes
For decades, General Motors vehicles (GM, Chevrolet, Buick, Cadillac, Pontiac, Oldsmobile, GMC) have relied on a unique and powerful data stream known as . While generic OBD-II scanners can read basic engine codes and live data on vehicles from 1996 onward, older GM models (primarily 1980–1995) and even some early OBD-II systems speak a different language. Enter the legendary solution: The GM Mode 22 Scan Tool by Terry . On your scanner, select “GM Enhanced” or “Manufacturer
: It is designed to utilize the "Mode 22" diagnostic request, a proprietary GM protocol used to retrieve specific data parameters (PIDs) that standard generic OBD-II Mode 01 requests may not cover.
: It is frequently bundled with ELM327 USB or Bluetooth diagnostic kits as part of a free software suite.