Part 2 of 3

DTC 26 - Quad-Driver (QDM) Circuit (Part 2 Of 3):

Quad-Driver (QDM) Circuit:

Circuit Description:

Quad-Driver Modules (QDM) are used to control the components shown in the illustration above. When the ECM is commanding a component "ON," the QDM closes the switch completing the circuit to ground.

Each QDM has a sense line and a fault line. When a component is commanded "ON," the voltage potential on the sense line is low and when the component is commanded "OFF," the voltage potential on the sense line is high.

DTC 26 will set when the ECM is commanding a QDM A controlled component 'ON" and the voltage potential on the sense line is high, or if the component is commanded "OFF" and the voltage potential on the sense line is low. QDM B will not set DTC 26.

Vehicles with a 3T40 transaxle will read "HIGH" until the TCC in-line switch is closed. To check, disconnect TCC connector and connect a test light between terminals "A" and "D". This should cause the Tech 1 to display "LOW" for QDM A with the engine running.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
3. This test will determine which circuit is out of specifications.

Diagnostic Aids:

Monitor the voltage at each terminal while moving related harness connectors, including ECM harness. If the failure is induced, the voltage will change. This may help locate the intermittent. Check for bent pins at ECM and ECM connector terminals. Also, ensure that the mid gear switch and CKT 232 is not open with the vehicle operating in park/neutral or 1st gear - This condition can cause a false DTC 26 to be set. Refer to DTC 27 chart for diagnosis. If DTC re-occurs with no apparent connector problem, replace ECM.