Chart C-1 ECM Quad Driver (QDR) Check

Chart C-1 - ECM QDR Check:

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 circuit is faulty, or could be "ON" at all times.

Important Points:


A. This procedure will not test all ECM functions. It will determine if a vehicle circuit has caused the ECMs QDR to fail.


B. Since the largest cause of QDR failure is faulty vehicle circuits, it is advisable that this procedure be used whenever ECM replacement is indicated, especially if the damaged ECM exhibits characteristics of a damaged QDR such as:

1. CEL/SES with no codes stored.

2. Engine will not start and/or ECM will not flash Code 12.

3. Flickering, intermittent, or dim CEL/SES.

4. Output (such as TCC) is inoperative, or "ON" at all times.

5. Engine misfires, surges or stalls.

6. "Scan" tool is erratic or inoperative.


The following procedure will not only tell which QDR is damaged, but in most cases, will indicate the specific circuit that most probably caused the damage to the ECM.

Required Tools:


1. Digital Multimeter (DVM) J-34029-A or equivalent (must have impedance of at least 10 megohm).