GM ALDL (Assembly Line Diagnostic Link) is a 12-pin connector used on GM vehicles from the early 1980s through 1995. The diagnostic protocol uses a single serial line at 160 or 8192 baud.
| Pin | Name | Function | Type |
|---|---|---|---|
| A | ABRT | Ground bridge pin for blink codes | GND |
| B | Diagnostic Request | Bridge to A for blink codes | I/O |
| C | Air Injection | Air pump relay signal | I/O |
| E | Serial Data | ALDL serial data 160 or 8192 baud | BUS |
| F | TCC Brake | TCC brake switch signal | I/O |
| M | Fuel Pump | Fuel pump monitor | I/O |
| P | DM Test | Diagnostic mode test | I/O |