Understanding the OBD2 pinout for General Motors (GM) vehicles is crucial for anyone involved in automotive diagnostics or repair, from professional mechanics to DIY enthusiasts. This guide provides a detailed look into the GM OBD2 pinout, ensuring you have the knowledge to effectively interface with your GM vehicle’s diagnostic system.
The On-Board Diagnostics II (OBD2) system became mandatory in the United States for all cars manufactured from 1996 onwards. For GM vehicles, the implementation of OBD2 and the specific pinouts have evolved over the years, particularly concerning the communication protocols used.
Standard GM OBD2 Pinout (1996-Present)
While the OBD2 standard provides a universal 16-pin connector, understanding the specific assignments for GM vehicles is essential. Here’s a breakdown of the standard OBD2 pinout used in most GM cars produced from 1996 onwards:
| Pin Number | Pin Name | Description |
|---|---|---|
| 1 | Low Speed GMLAN Serial Data. This pin is used for various vehicle modules communicating on the Low Speed GMLAN (Global Medium-speed Local Area Network). Modules connected through this pin can include: Amplifier (Amp), Rear seat audio (RSA), Vehicle communication interface module (VCIM), Digital radio receiver (DRR), Inside rearview mirror module (ISRVM), Instrument panel cluster (IPC), Body control module (BCM), Theft deterrent module (TDM), Heater ventilation and air conditioning (HVAC), Radio, Driver door switch (DDS), Passenger door switch (PDS), Articulating running board module (ARBM), Ultrasonic park assist (UPA), Memory seat module (MSM), Liftgate module (LGM), Passenger presence system (PPS), Inflatable restraint vehicle rollover sensor (ROS), and Inflatable restraint sensing and diagnostic module (SDM). | |
| 2 | J1708 | SAE J1708 Serial Data (Trucks only). This pin is typically used for SAE J1708 communication, which is more common in trucks and heavier vehicles. |
| 3 | PTLAN (+) | High speed hybrid GMLAN serial data bus (+) terminal (with Hybrid propulsion electric). Used in hybrid electric vehicles for high-speed communication on the GMLAN network. |
| 4 | GND | Chassis ground. Provides a ground connection to the vehicle chassis. |
| 5 | SGND | Signal Ground. Signal ground, often used to reduce electrical noise in sensor readings. |
| 6 | HS-CAN (+) | High Speed GMLAN Serial Data Bus +. This is the High-Speed CAN (Controller Area Network) bus line (+). It’s the primary communication network for critical systems like the engine control module (ECM), transmission control module (TCM), body control module (BCM), and other modules such as vehicle communication interface module (VCIM), 4WD control module, EBCM (Electronic Brake Control Module), and suspension control module, depending on the vehicle’s options (RPO – Regular Production Option codes). |
| 7 | KW2000 | Keyword 2000 Serial Data (on some models) / SAE J1708 Serial Data A (Trucks only). This pin can be used for Keyword 2000 (KWP2000) communication protocol on certain GM models or SAE J1708 Serial Data A in trucks. |
| 8 | Central Control Module Diagnosis Enable (some Holden models). Specific to some Holden (GM subsidiary in Australia) models, used for enabling diagnosis of the central control module. | |
| 11 | PTLAN (-) | High speed hybrid GMLAN serial data bus (-) terminal (with Hybrid propulsion electric). Complementary pin to pin 3 for high-speed GMLAN communication in hybrid vehicles. |
| 14 | HS-CAN (-) | High Speed GMLAN Serial Data Bus -. The negative (-) line for the High-Speed CAN bus, completing the differential CAN communication circuit. |
| 15 | J1708 B | SAE J1708 Serial Data B (Trucks only). The second line for SAE J1708 communication, often used in conjunction with pin 2 in trucks. |
| 16 | Battery+ | Battery Positive Voltage. Provides battery power to the OBD2 scan tool. |
Understanding these pin assignments is crucial when using an OBD2 scanner or other diagnostic tools on GM vehicles. Incorrect connections can lead to communication errors or potentially damage your vehicle’s electronic systems or the scan tool itself.
Alt text: Standard GM OBD2 connector pinout diagram illustrating pin numbers and their corresponding functions, including GMLAN, CAN bus, and power.
Pre-2000 GM OBD2 Connector Variations
Before the standardization of OBD2 was fully adopted, some pre-2000 GM vehicles might have slight variations in their OBD2 pinouts. While still using the 16-pin connector, the pin assignments could differ from the later standard. Here’s a typical pre-2000 GM OBD2 pinout configuration:
| Pin | Wire Color | Function |
|---|---|---|
| 2 | PPL | Serial Data Signal-Class B |
| 4 | BLK | Ground |
| 5 | BLK/WHT | VCM Ground (Vehicle Control Module Ground) |
| 8 | BLK/WHT | Keyless Entry Program Enable Signal |
| 9 | TAN | SIR Serial Data (Supplemental Inflatable Restraint – Airbag) |
| 12 | TAN/WHT | Diagnostic Signal (ABS) / (15,000 GVW Only) |
| 13 | ORN | Diagnostic Signal-Transfer Case Control Module |
| 14 | GRN DK | Diagnostic Signal-Entertainment and Comfort |
| 16 | ORN | Battery |
It’s important to note that for vehicles manufactured before 2000, you should always verify the specific pinout for your model to ensure correct diagnostic connections. Consulting a vehicle-specific repair manual is highly recommended for these older models.
Alt text: Pre-2000 GM OBD2 pinout diagram detailing wire colors and functions like Class B serial data, VCM ground, SIR data, and diagnostic signals.
GM OBD2 Protocols and Compatibility
GM vehicles have utilized different OBD2 communication protocols over the years. Understanding these protocols is crucial for selecting the right OBD2 scanner and interpreting the data correctly.
- J1850 VPW (Variable Pulse Width Modulation): Used extensively in GM vehicles produced from 1996 to the early 2000s. Many models between 1996 and 2003, and some even up to 2006, utilize J1850 VPW.
- CAN (Controller Area Network): Gradually introduced in the early 2000s and became the predominant protocol for GM vehicles manufactured after 2006. Some models from 2003-2006 might use either J1850 VPW or CAN.
- ISO 9141 & KWP2000: While less common than J1850 VPW and CAN in North American GM vehicles, some models, particularly in international markets or certain engine types, might use ISO 9141 or KWP2000 protocols.
OBD-2 Compatibility List (Selected GM Models):
| Model | Engine | Year (starting from) | OBD-2 Protocol |
|---|---|---|---|
| Buick Century | 2002 | VPW J1850 | |
| Buick Rivera | 1998 | VPW J1850 | |
| Buick Skylark | 1996 | VPW J1850 | |
| Cadillac Deville | 2000 | VPW J1850 | |
| Cadillac Eldorado | 1998 | VPW J1850 | |
| GMC Jimmy | 1999 | VPW J1850 | |
| GMC K2500 | 1997 | VPW J1850 | |
| GMC Lumina | 2001 | VPW J1850 | |
| GMC Yukon | 1998 | VPW J1850 | |
| Chevrolet Astra | 2.0 Flex Power, Gasoline (127 HP) | 2004 | ISO 14230-4, ISO 9141-2 |
| Chevrolet Aveo | 1.4, Gasoline (60HP) | 2005 | KWP FAST |
| Chevrolet Blazer | 1995 | VPW J1850 | |
| Chevrolet Camaro | 1997 | VPW J1850 | |
| Chevrolet Caprice | 1996 | VPW J1850 | |
| Chevrolet Captiva | 2.0 VCDI, Diesel (150HP) | 2006 | CAN 11bit (500kb) |
| Chevrolet Cavalier | 1996 | VPW J1850 | |
| Chevrolet Cobalt | Gasoline (145 HP) | 2006 | CAN |
| Chevrolet Corvette | 2000 | VPW J1850 | |
| Chevrolet Cruze | 2.0 VCDi, Diesel (150HP) | 2010 | CAN 11bit (500kb) |
| Chevrolet Epica | 2.5, Gasoline (155HP) | 2004 | KWP FAST |
| Chevrolet Express van | V8 5.3L, Gasoline (300HP) | 2003 | VPN |
| Chevrolet Impala | 2000 | VPW J1850 | |
| Chevrolet Malibu | 1997 | ||
| Chevrolet Orlando | 1.8, Gasoline (146HP) | 2012 | CAN 11bit (500kb) |
| Chevrolet Silverado | 2002 | VPW J1850 | |
| Chevrolet Tahoe | 1996 | VPW J1850 | |
| Chevrolet Trailblazer | Gasoline (270 HP) | 2002 | PWM J1850 |
| Chevrolet Venture | 1998 | VPW J1850 |
Note: This list is not exhaustive and protocol compatibility can vary based on specific vehicle configurations and market region.
When working with GM vehicles, especially older models, it’s essential to:
- Identify the Model Year: Determine the year of manufacture to understand the likely OBD2 protocol and pinout.
- Consult a Repair Manual: Refer to the vehicle’s repair manual for the most accurate pinout and protocol information.
- Use a Compatible Scanner: Ensure your OBD2 scanner supports the correct protocol (J1850 VPW, CAN, etc.) for your GM vehicle.
By understanding the nuances of GM OBD2 pinouts and protocols, you can confidently diagnose and repair a wide range of General Motors vehicles, ensuring accurate and efficient automotive servicing.
