DRB II vs DRB III vs OBD II: Chrysler Diagnostic Scan Tools Explained
The Evolution of Chrysler Diagnostic Tools: From DRB II to DRB III
If you’re working on a Chrysler, Dodge, or Jeep vehicle from the 1980s through the 2000s, you’ve probably encountered references to the DRB—Chrysler’s proprietary diagnostic tool. But there’s often confusion about what these tools can do, how they differ from standard OBD II scanners, and whether one can replace the other. The short answer: they serve different purposes, and for older Dodge Dakotas, understanding the distinction matters.
What Was the DRB II?
The DRB II was Chrysler’s diagnostic readout box designed for vehicles from the 1980s and early 1990s. Unlike later tools, the DRB II lacked onboard memory and instead relied on removable support cards—essentially cartridges that contained vehicle-specific diagnostic data. This meant you had to have the correct support card loaded to diagnose a particular vehicle, making the system less flexible than what came later.
The DRB III: A Major Step Forward
The DRB III represented a significant advancement. It featured onboard memory, eliminating the need for external support cards. More importantly, it expanded diagnostic coverage backward and forward—eventually supporting vehicles from the mid-1980s all the way through 2008 (for non-CAN architecture vehicles). The DRB III also introduced upgradable software, meaning dealers could update the tool as new vehicles and systems were added.
The DRB III offers capabilities that go well beyond simple code reading. It provides detailed descriptions of fault codes, allows for advanced bidirectional testing, and on modern modules, enables programming and calibration. This makes it far more powerful than a generic scan tool for in-depth diagnostics.
OBD II Scanners: A Different Tool for a Different Purpose
Here’s where confusion commonly arises. OBD II (On-Board Diagnostics, Generation 2) became mandatory on all vehicles sold in the US starting in 1996. It’s a standardized emissions diagnostic protocol—not a proprietary Chrysler system. A $50 to $150 OBD II scanner can read generic and manufacturer-specific codes from any vehicle’s engine and transmission modules once that vehicle is OBD II equipped.
However, your 1993 Dodge Dakota predates OBD II. It doesn’t have an OBD port at all. You retrieve codes by cycling the key and counting flashes of the check engine light. This is why a generic OBD II scanner won’t help with a 1993 Dakota.
The RWAL Brake System Limitation
One of the most important distinctions involves the antilock brake system. Many Dodge trucks and Dakotas came equipped with Kelsey-Hayes RWAL (Rear Wheel Anti-Lock) brakes—a single-channel system that monitors only the rear wheels. The brake module stores its own fault codes separately from the engine computer.
Here’s the catch: standard OBD II scanners cannot read RWAL codes. They simply don’t have the protocol or the adapters to communicate with that system. The DRB III, however, includes adapters and software specifically designed to read and diagnose RWAL codes. If your Dakota has a brake warning light and RWAL-equipped brakes, you’ll need a tool capable of reading those codes—and a basic OBD II scanner won’t do it.
Which Tool Do You Actually Need?
For a 1993 Dodge Dakota or similar-era Chrysler vehicle, the reality is that a generic OBD II scanner is of limited use. You either need a DRB (II or III, depending on availability), a used scanner designed for pre-OBD II Chrysler vehicles, or you can go the old-fashioned route of learning how to read codes by the key-cycling method.
If you do find a used DRB tool, the DRB III is preferable if you can locate one, since it has better software support and broader vehicle coverage. The DRB II will work but requires that you find the correct support card for your vehicle year and engine, which can be challenging.
The takeaway: OBD II scanners are great for modern vehicles and specific emissions-related diagnostics, but they’re not a replacement for Chrysler’s factory diagnostic tools when working on older Dakotas, Rams, and Jeeps.
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