The On-Board Diagnostics II (OBD2) system is a cornerstone of modern automotive diagnostics, providing access to a wealth of data about a vehicle’s health and performance. For General Motors (GM) vehicles, understanding the specific signals transmitted through the OBD2 connector is crucial for accurate troubleshooting and repair, especially when dealing with complex systems like the Anti-lock Braking System (ABS). This guide delves into the intricacies of GM OBD2 connector signals, with a particular focus on ABS diagnostics, offering a comprehensive overview for technicians and automotive enthusiasts alike.
Understanding GM OBD2 Pinouts and Protocols
The OBD2 connector in GM vehicles serves as a gateway to various communication networks within the car. However, the protocols and pin assignments have evolved over time. Early GM OBD2 implementations, particularly in vehicles produced between 1996 and 2003, predominantly utilized the J1850-VPW (Variable Pulse Width Modulation) interface. As technology advanced, GM transitioned to CAN (Controller Area Network) bus systems. Vehicles manufactured from 2003 to 2006 might employ either J1850-VPW or CAN, depending on the model and specific systems. Post-2006, CAN bus became the standard communication protocol for most GM vehicles.
To effectively diagnose and repair GM vehicles, it’s essential to understand the function of each pin within the OBD2 connector. Below is a detailed breakdown of the standard GM OBD2 connector pinout, highlighting the signals associated with each pin:
Standard GM OBD2 Connector Pinout (Post-2000)
| Pin Number | Pin Name | Description |
|---|---|---|
| 1 | Low Speed GMLAN Serial Data. – Used for communication with various modules such as 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 (Primarily used in Trucks) |
| 3 | PTLAN (+) | High speed hybrid GMLAN serial data bus (+) terminal (Used in Hybrid propulsion electric vehicles) |
| 4 | GND | Chassis Ground |
| 5 | SGND | Signal Ground |
| 6 | HS-CAN (+) | High Speed GMLAN Serial Data Bus +. This is a critical pin for communication between core vehicle modules like the Body Control Module (BCM), Engine Control Module (ECM), Transmission Control Module (TCM), Vehicle Communication Interface Module (VCIM), 4WD Control Module, Electronic Brake Control Module (EBCM – crucial for ABS), and Suspension Control Module (depending on vehicle options – RPO codes). |
| 7 | KW2000 | Keyword 2000 Serial Data (on some older models) / SAE J1708 Serial Data A (Trucks only) |
| 8 | Central Control Module Diagnosis Enable (Specific to some Holden models) | |
| 11 | PTLAN (-) | High speed hybrid GMLAN serial data bus (-) terminal (Used in Hybrid propulsion electric vehicles) |
| 14 | HS-CAN(-) | High Speed GMLAN Serial Data Bus – (E&C). Complementary to Pin 6, forming the High-Speed CAN bus differential pair. |
| 15 | J1708 B | SAE J1708 Serial Data B (Primarily used in Trucks) |
| 16 | Battery+ | Battery Positive Voltage (Power supply for the OBD2 scan tool) |
It’s important to note that pinout configurations can sometimes vary slightly depending on the specific GM model and year.
Pre-2000 GM OBD2 Connector Variations
For GM vehicles manufactured before the year 2000, the OBD2 connector pinout might exhibit some differences compared to the later standard. While still OBD2 compliant, these earlier models sometimes utilized different pin assignments for specific diagnostic signals. Here’s a representation of a common pre-2000 GM OBD2 pin configuration:
| Pin | Wire Color | Function |
|---|---|---|
| 2 | PPL (Purple) | Serial Data Signal-Class B (Often J1850 VPW) |
| 4 | BLK (Black) | Ground |
| 5 | BLK/WHT (Black/White) | VCM Ground (Vehicle Control Module Ground) |
| 8 | BLK/WHT (Black/White) | Keyless Entry Program Enable Signal (Specific function, less related to general diagnostics) |
| 9 | TAN | SIR Serial Data (Supplemental Inflatable Restraint – Airbag System) |
| 12 | TAN/WHT (Tan/White) | Diagnostic Signal (ABS)/(15,000 GVW Only) – Crucially, this pin is often designated for ABS diagnostic signals in older GM vehicles, especially those with higher GVW (Gross Vehicle Weight). |
| 13 | ORN (Orange) | Diagnostic Signal-Transfer Case Control Module (4WD/AWD systems) |
| 14 | GRN DK (Dark Green) | Diagnostic Signal-Entertainment and Comfort systems |
| 16 | ORN (Orange) | Battery (Power supply) |
Focus on ABS Connector Signals:
While the term “ABS connector signals” might broadly refer to the communication related to the ABS module, in the context of OBD2, it usually points to the diagnostic signals accessible through the OBD2 port that are relevant to the ABS.
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High-Speed CAN Bus (Pins 6 & 14): In CAN-based GM vehicles (generally post-2003/2006), the ABS module (EBCM – Electronic Brake Control Module) communicates over the High-Speed CAN bus. Pins 6 (HS-CAN +) and 14 (HS-CAN -) are the pathways for retrieving ABS fault codes, live data, and potentially initiating diagnostic tests related to the ABS system using a compatible OBD2 scan tool.
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Diagnostic Signal (ABS) – Pin 12 (Pre-2000): For older GM vehicles with the pre-2000 pinout configuration, Pin 12 (TAN/WHT wire) is specifically designated as “Diagnostic Signal (ABS)”. This signifies that diagnostic communication related to the ABS system might be routed through this pin in these older models, particularly those around or before the mid-to-late 1990s.
OBD2 Compatibility and Protocols for GM Models:
Understanding the OBD2 protocol used by a specific GM model is vital for selecting the correct scan tool and ensuring successful communication. GM vehicles have employed various OBD2 protocols, including:
- VPW J1850: Common in older GM vehicles (1996-2005ish).
- CAN (various standards, often 11-bit 500kbps): Predominant in newer GM vehicles (2006 onwards).
- ISO 14230-4 (KWP2000): Used in some models, particularly in the early 2000s and in some international markets.
- ISO 9141-2: Another ISO standard protocol, less common than KWP2000 in GM but present in some models.
Here’s a compatibility list showcasing OBD2 protocols for various GM models (note: this list is not exhaustive and serves as a general guide):
| 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 |
| 1.6, Gasoline (103HP) | 2005 | KWP FAST | |
| 1.6, Gasoline (103HP) | 2007 | KWP FAST | |
| 1.2, Gasoline (70HP) | 2008 | KWP FAST | |
| 1.5, Gasoline (?HP) | 2008 | KWP FAST | |
| Gasoline (84 HP) | 2009 | ISO 14230-4 | |
| 1.2, Gasoline or LPG (82HP) | 2009 | KWP FAST | |
| Chevrolet Blazer | 1995 | VPW J1850 | |
| Chevrolet Blazer LT | Gasoline (191 HP) | 1997 | VPW J1850 |
| Chevrolet Camaro | 1997 | VPW J1850 | |
| 1997 | ISO 14230-4, ISO 9141-2 | ||
| 1998 | VPW J1850 | ||
| 3.8 V6, Gasoline (193HP) | 1998 | VPN | |
| 1999 | VPW J1850 | ||
| 5.7 LS1, Gasoline (288HP) | 1999 | VPN | |
| 2000 | VPW J1850 | ||
| L36, Gasoline (191 HP) | 2002 | VPW J1850 | |
| 6.2 V8, Gasoline (405HP) | 2012 | CAN 11bit (500kb) | |
| Chevrolet Caprice | 1996 | VPW J1850 | |
| Chevrolet Captiva | 2.0 VCDI, Diesel (150HP) | 2006 | CAN 11bit (500kb) |
| 2.2 VCDI, Diesel (163HP) | 2011 | CAN 11bit (500kb) | |
| Chevrolet Cavalier | 1996 | VPW J1850 | |
| 1998 | VPW J1850 | ||
| 1999 | VPW J1850 | ||
| Chevrolet Cobalt | Gasoline (145 HP) | 2006 | CAN |
| Chevrolet Corvette | 2000 | VPW J1850 | |
| V8, Gasoline (400HP) | 2007 | CAN 11bit (500kb) | |
| Chevrolet Corvette C5 | 5.7 V8, Gasoline (350HP) | 2003 | VPN |
| Chevrolet Corvette C6 | 6, Gasoline (404HP) | 2005 | ISO 9141 |
| LS7, Gasoline (512HP) | 2007 | CAN 11bit (500kb) | |
| 6.2, Gasoline (436HP) | 2008 | CAN 11bit (500kb) | |
| Chevrolet Cruze | 2.0 VCDi, Diesel (150HP) | 2010 | CAN 11bit (500kb) |
| 2.0 VCDI, Diesel (163HP) | 2011 | CAN 11bit (500kb) | |
| Chevrolet Epica | 2.5, Gasoline (155HP) | 2004 | KWP FAST |
| 2.0 vdCi, Diesel (150HP) | 2007 | CAN 11bit (500kb) | |
| Chevrolet Evanda | Gasoline (176 HP) | 2005 | |
| Chevrolet Express van | V8 5.3L, Gasoline (300HP) | 2003 | VPN |
| Chevrolet HHR | Gasoline (168 HP) | 2008 | |
| Chevrolet Impala | 2000 | VPW J1850 | |
| 2002 | VPW J1850 | ||
| Chevrolet Kalos | 1.4 SE, Gasoline (93 HP) | 2005 | ISO 14230-4, ISO 9141-2 |
| 1.4 16V, Gasoline (93 HP) | 2006 | ISO 14230-4 | |
| Chevrolet Lumina | 1996 | VPW J1850 | |
| Chevrolet Malibu | 1997 | ||
| Chevrolet Malibu | 3.1 V6, Gasoline (150HP) | 2000 | VPN |
| Chevrolet Matiz | 1.0 SE LPG.i, Gasoline (64HP) | 2006 | KWP FAST |
| Gasoline (66 HP) | 2007 | ISO 14230-4, ISO 9141-2 | |
| 0.8, Gasoline (65HP) | 2009 | KWP FAST | |
| Chevrolet Nuriba | 1.8 BVA, Gasoline or LPG (122HP) | 2006 | KWP FAST |
| Chevrolet Optra | 1.6, Gasoline (109HP) | 2005 | KWP FAST |
| Chevrolet Orlando | 1.8, Gasoline (146HP) | 2012 | CAN 11bit (500kb) |
| 2.0 HDi, Diesel (163HP) | 2012 | CAN 11bit (500kb) | |
| Chevrolet Rezzo | 1.6 16v, Gasoline or LPG (107HP) | 2005 | ISO 9141 |
| Chevrolet S10 | 2000 | VPW J1850 | |
| Chevrolet Silverado | 2002 | VPW J1850 | |
| 6.5, Diesel (194HP) | 1996 | VPN | |
| Chevrolet Spark | Gasoline (81 HP) | 2008 | |
| 1, Gasoline (68HP) | 2011 | KWP FAST | |
| Chevrolet Tahoe | 1996 | VPW J1850 | |
| 5.7, Gasoline (265HP) | 1998 | VPN | |
| 5.3, Gasoline (275HP) | 2001 | VPN | |
| 5.3 V8, Gasoline (290HP) | 2005 | VPN | |
| Chevrolet Trailblazer | Gasoline (270 HP) | 2002 | PWM J1850 |
| Gasoline (270 HP) | 2002 | ||
| Chevrolet Trans Sport | Gasoline (184 HP) | 2000 | |
| Gasoline (186 HP) | 2003 | ||
| Chevrolet Transsport | Gasoline (184 HP) | 1997 | VPW J1850 |
| Chevrolet Uplander | 3.9, Gasoline (200HP) | 2007 | CAN 11bit (500kb) |
| 3.9, Gasoline (250HP) | 2007 | CAN 11bit (500kb) | |
| Chevrolet Venture | 1998 | VPW J1850 | |
| 3.4, Gasoline (160HP) | 2002 | VPN |
Note that “VPN” and blank entries in the “OBD-2 Protocol” column within the original data might indicate incomplete information or variations. Always consult vehicle-specific service manuals for the most accurate protocol details.
Conclusion:
Successfully diagnosing ABS and other systems in GM vehicles hinges on a solid understanding of the OBD2 connector and the signals it carries. Knowing the pinouts, the evolution of communication protocols from J1850-VPW to CAN, and the specific pin assignments for diagnostic signals, especially those related to ABS (like Pin 12 in older models and the CAN bus pins in newer ones), empowers technicians to accurately interpret diagnostic data and perform effective repairs. Always refer to vehicle-specific documentation and utilize appropriate OBD2 scan tools compatible with the GM vehicle’s communication protocol for reliable diagnostic outcomes.
