The OBDII (On-Board Diagnostics II) port is a crucial interface for diagnosing vehicle issues. This guide focuses on the Gm Obdii Pinout, providing a detailed breakdown of the pin assignments and communication protocols used in General Motors vehicles. Understanding the GM OBDII pinout is essential for mechanics, technicians, and car enthusiasts working with GM vehicles.
Understanding the GM OBDII Connector
The OBDII connector in GM vehicles, like in most cars, is a standardized 16-pin connector. However, the specific pin assignments and communication protocols can vary depending on the vehicle’s model year and the specific systems being accessed.
GM OBDII Pinout Chart (Post-2000)
| Pin Number | Pin Name | Description |
|---|---|---|
| 1 | Low Speed GMLAN Serial Data | Used for communication between various modules like the Amplifier, Rear Seat Audio, Vehicle Communication Interface Module (VCIM), and more. |
| 2 | J1708 | SAE J1708 Serial Data (Primarily for Trucks) |
| 3 | PTLAN (+) | High-speed hybrid GMLAN serial data bus positive terminal (for Hybrid vehicles). |
| 4 | GND | Chassis Ground |
| 5 | SGND | Signal Ground |
| 6 | HS-CAN (+) | High-Speed GMLAN Serial Data Bus positive terminal. Used for communication between critical modules like the Body Control Module (BCM), Engine Control Module (ECM), and Transmission Control Module (TCM). |
| 7 | KW200/J1708 | Keyword 2000 Serial Data (on some models) / SAE J1708 Serial Data A (Trucks). |
| 8 | Diagnosis Enable | Central Control Module Diagnosis Enable (specific Holden models). |
| 11 | PTLAN (-) | High-speed hybrid GMLAN serial data bus negative terminal (for Hybrid vehicles). |
| 14 | HS-CAN(-) | High-Speed GMLAN Serial Data Bus negative terminal. |
| 15 | J1708 B | SAE J1708 Serial Data B (Primarily for Trucks) |
| 16 | Battery+ | Battery Positive Voltage |
GM OBDII Pinout (Pre-2000)
Pre-2000 GM vehicles may have a different pinout configuration. While variations exist, a common configuration is as follows:
| Pin | Wire Color | Function |
|---|---|---|
| 2 | Purple | Serial Data Signal – Class B |
| 4 | Black | Ground |
| 5 | Black/White | VCM Ground |
| 8 | Black/White | Keyless Entry Program Enable Signal |
| 9 | Tan | SIR Serial Data |
| 12 | Tan/White | Diagnostic Signal (ABS) / (15,000 GVW Only) |
| 13 | Orange | Diagnostic Signal – Transfer Case Control Module |
| 14 | Dark Green | Diagnostic Signal – Entertainment and Comfort |
| 16 | Orange | Battery |
GM OBDII Communication Protocols
GM vehicles have utilized different communication protocols over the years:
- J1850-VPW: Common in GM cars produced between 1996 and 2003.
- CAN (Controller Area Network): Gradually adopted from 2003 onwards and became prevalent in most models after 2006. CAN offers faster communication speeds and greater bandwidth.
- ISO 9141-2 and ISO 14230-4 (KWP2000): Used in some specific models, particularly those manufactured for international markets.
Fig 1: A standard OBDII connector.
Fig 2: An OBDII cable connected to a vehicle’s port.
Conclusion
Understanding the GM OBDII pinout and communication protocols is crucial for accurate vehicle diagnostics. This guide provides a foundation for interpreting the signals and data transmitted through the OBDII port, enabling effective troubleshooting and repair of GM vehicles. Always consult the specific vehicle’s service manual for the most accurate and up-to-date information.
