ELD Cables: 9 Pin vs 6 Pin vs OBD2 (Which Do You Need?)
Rules, prices and device details on this page were checked October 2026 against the official sources listed at the bottom. Where a provider doesn't publish a number, we say so instead of guessing.
Ordering the wrong ELD cable is one of the most common setup mistakes. The device arrives, you crawl under the dash and the plug doesn't fit. The fix is simple: know which diagnostic connector your truck has before you order. This guide walks through the main connector types, how to spot each one and what's typical by make and model year.
One caution up front. The patterns below are general. Truck makers changed connectors at different times, and individual trucks can differ. Always look at the actual port and confirm with your ELD vendor before you buy.
Connector Types
9 pin (J1939)
The round 9 pin connector is the most common diagnostic port on heavy trucks built from the early 2000s on. It carries engine data over the J1939 network. There are two versions you'll run into:
- Black 9 pin (Type 1). Common on trucks built up to the mid 2010s.
- Green 9 pin (Type 2). Found on many newer trucks. It supports a faster data rate, and its shape is slightly different, so some older black cables won't fit it. Cables built for Type 2 usually work with black ports as well, but check with your vendor.
6 pin (J1708)
The round 6 pin connector is the older heavy truck diagnostic port. It's mostly found on trucks from the 1990s and early 2000s. If your truck has a 6 pin port, check the engine year too, since some of these trucks may qualify for the pre 2000 engine exemption.
16 pin OBD style
The 16 pin trapezoid connector looks like the port in a car. Many medium duty trucks and light commercial vehicles use it. Some heavy trucks do too, especially newer Volvo and Mack models, which moved to a heavy duty 16 pin port in the mid 2010s. Heavy duty 16 pin ports can be wired differently from car ports, so use a cable made for your truck, not a generic car adapter.
By Truck Make
| Make | Typical connector | Notes |
|---|---|---|
| Freightliner, Western Star | 9 pin (black on older, green on newer) | Check color on trucks from the mid 2010s |
| Peterbilt, Kenworth | 9 pin (black on older, green on newer) | Same as above |
| International | 9 pin | Some newer models use green Type 2 |
| Volvo, Mack (about 2001 to 2013) | 9 pin | Older models may have 6 pin |
| Volvo, Mack (about 2014 and newer) | Heavy duty 16 pin OBD style | Needs a Volvo/Mack specific cable |
| Older heavy trucks (1990s) | 6 pin | May qualify for the pre 2000 exception |
| Medium duty and box trucks | 16 pin OBD style | Common on gas and light diesel models |
Year ranges are approximate. The changeover varied by model and plant, so use the table as a starting point and confirm by looking at the port.
How to Check Your Truck
- Find the diagnostic port. It's usually under the dash on the driver's side, near the steering column or the kick panel.
- Count the pins and note the shape. Round with 9 pins, round with 6 pins or flat trapezoid with 16 pins.
- If it's a 9 pin port, note the color: black or green.
- Write down the make, model and year.
- Take a photo and send it to your ELD vendor if you're not sure.
Adapters
There are a few adapter types worth knowing about:
- Y or T cables. These split the port so your ELD and a mechanic's scan tool or another device can share it. They also let you mount the ELD module out of the way.
- Extension cables. Useful when the port is in an awkward spot.
- Conversion adapters. Some vendors sell adapters between connector types. They can work, but a cable made for your port is usually more reliable.
Loose or poor quality connections are a common cause of ELD malfunctions. If your ELD keeps dropping its engine connection, check the cable and port first. Our ELD malfunction guide explains what to do if a device fails on the road.
Where to Buy
Buy cables from your ELD provider whenever you can. Each ELD module has its own device side plug, so a cable from another brand may not fit even if the truck side is right. Most providers include one cable with each device and sell extra types for mixed fleets. If you buy from a third party, make sure it's listed as compatible with your exact ELD model.
For a wider look at device types, see our ELD hardware types guide.
Rules and data checked October 2026.
Frequently Asked Questions
Which ELD cable do I need?
Look at your truck diagnostic port. Most heavy trucks use a round 9 pin port, older trucks a 6 pin port, and many newer Volvo and Mack trucks and medium duty trucks a 16 pin OBD style port.
What is the difference between black and green 9 pin connectors?
Green Type 2 ports are found on many newer trucks and support a faster data rate. Some older black cables will not fit a green port.
Can I use a car OBD2 cable on a truck?
Not reliably. Heavy duty 16 pin ports can be wired differently, so use a cable made for your truck and ELD.
Where should I buy an ELD cable?
From your ELD provider, since the device side plug is specific to each ELD model.
Sources
All prices, terms and registration details were checked October 2026 on the pages below. Providers change pricing often, so confirm before you buy.