Somerset V6-181 3.0L (1986)
QDR Application Chart for Chart C-1
CHART C-1 - ECM QUAD DRIVER (QDR) CHECK
QDR History and Significance:
Since 1982, most ECMs have used an integrated circuit (1C) in place of separate transistors to turn "ON" or "OFF" different components controlled by
the ECM. These ICs are called QUAD drivers (QDR). Each QDR has four separate outputs, meaning it can turn "ON" or "OFF" four different items
independently.
For example, one QDR may operate the CEL/SES, the canister purge solenoid, the A/C relay and the EGR solenoid. The QDR may not always be
connected to four different outputs. In applications where the QDR drives devices that require increased current flow (such as TCC solenoid, M/C
solenoid, etc.) it is common for two of the QDR outputs to be used to drive a single solenoid. This allows the QDR to safely handle the extra current that
these solenoids require. Because of this a QDR will not always control 4 different solenoids, it may control only 2 or 3.
A failed QDR usually results in an ECM output becoming either shorted or open. Many times all four QDR outputs will be inoperative if just one vehicle
