Skyhawk L4-121 2.0L Turbo VIN M FI (1987)
ECM Quad Driver Application Chart
CHART C-1 ECM QUAD DRIIVER CHECK (QDR)
DESCRIPTION
Many ECM's use an integrated circuit (IC) instead of individual transistors to operate different components that are controlled by the ECM. These IC's
are called QUAD DRIVERS (QDR's). Each QDR has 4 seperate outputs so it can operate 4 different items independently.
As an example, one QDR may operate the check engine light, the canister purge solenoid, the EGR solenoid and the A/C relay. The QDR is not always
connected to 4 different outputs. Where more current flow is required (such as the TCC solenoid or M/C solenoid) 2 of the outputs may be used to drive
the same device.
A bad QDR normally causes an ECM output to go open or shorted. Often all 4 outputs will not operate even if only 1 circuit is faulty.
TESTING NOTES
1.
This procedure will not test all ECM operations. It will determine if a circuit caused the ECM QDR to fail.
2.
Because the most common cause of QDR failure is faulty vehicle circuits you are urged to use this procedure whenever an ECM is replaced,
especially when:
