Diagnostic readout connector and the DRB

by Bob O’Neill and Bob Lincoln

A serial data connection to the logic module is provided to connect a ‘data reader’ to the logic module. This diagnostic tool provides the ability to read fault codes rather than using the key dance method to read the codes using the power loss lamp.

The diagnostic tool (the official dealer tool is called the DRB) is also used to look at the inputs from sensors and switches to the logic module.  This tool can also be used to perform actuation test modes or ATM where the logic module receives instructions from the diagnostic tool to cycle circuits on and off testing them.  The tests available are a function of the diagnostic tool being used.  The connector is located under hood on the driver’s side fender well.

Most independent garages have a diagnostic tool, since some common procedures require it, and it can save a great deal of time. The system can also clear codes immediately without having to disconnect the battery.

Note that there is another tool less sophisticated (and cheaper) than the DRB, but hard to acquire: the C-4805 Diagnostic Read-Out Tool.

Newer cars phased in a more universal system with many more codes whose meaning was standardized across makers; the OBD II system did not appear with the 2.2 or 2.5 liter engines, starting with their replacements (e.g. the Neon). At Chrysler it was used starting in 1994 on the new Ram, and was fully implemented in 1998. Scanners for this system are common and many (such as the AutoTap and Palmer Engineering systems) use Palm Pilots or laptops to control what is displayed. Unfortunately there are two standards for OBD code readers; Chrysler used the common American system until the debut of the LX (300/Charger/Magnum).

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