OBD-II (On-Board Diagnostics, Second Generation) connectors are standardized across vehicles, but the communication protocols they use can vary. This article focuses on the J1850 PWM protocol and its corresponding pin configuration within the OBD-II connector, primarily used in Ford vehicles. Understanding this information is crucial for choosing the correct OBD-II reader.
Identifying Your Vehicle’s Communication Protocol
Different car manufacturers use different OBD-II communication protocols. Generally:
- GM: SAE J1850 VPW (Variable Pulse Width Modulation)
- Chrysler, European, and most Asian imports: ISO 9141-2
- Ford: SAE J1850 PWM (Pulse Width Modulation)
There can be exceptions, such as certain captive imports. For example, the Cadillac Catera (a German Opel derivative) uses the European ISO 9141-2 protocol.
J1850 PWM and the OBD-II Connector
For vehicles manufactured in 1996 and later, the OBD-II connector itself can provide clues about the communication protocol in use. You can determine the protocol by checking for metallic contacts in specific pins:
- J1850 VPW: Pins 2, 4, 5, and 16 should have contacts, while pin 10 should not.
- ISO 9141-2: Pins 4, 5, 7, 15, and 16 should have contacts.
- J1850 PWM: Pins 2, 4, 5, 10, and 16 should have contacts. This is the key configuration for Ford vehicles.
Importance of Correct Pin Identification for J1850 PWM
Correctly identifying the presence of metallic contacts in pins 2, 4, 5, 10, and 16 confirms the use of the J1850 PWM protocol. This is essential for selecting a compatible OBD-II reader for Ford vehicles from this era.
Pre-OBD-II Considerations
Even if your vehicle has the 16-pin OBD-II connector, the presence of the expected pin contacts doesn’t guarantee OBD-II compliance. Some pre-1996 vehicles may have the connector but not utilize the OBD-II standard. Always verify your vehicle’s model year and OBD-II compliance before purchasing a reader.
Conclusion
Understanding the J1850 PWM protocol and its associated pin configuration within the OBD-II connector is crucial for diagnosing and troubleshooting Ford vehicles. By verifying the presence of contacts in pins 2, 4, 5, 10, and 16, you can confirm J1850 PWM usage and select the appropriate OBD-II diagnostic tools. Remember to double-check your vehicle’s specifications to ensure compatibility, especially for models manufactured before 1996.
