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Questions and Answers

Quad-Driver Modules

Q. I decoded the engine light and came up with two codes, 12 and 26. The vehicle has a manual transmission. The code book states the "Quad-Module is receiving improper voltage or quad-module error at number one. I looked in the manual for the Quad-module and found none.

Hopefully you can shed some light on the subject.

A. Quad-Driver Modules (QDM) are a kind of switch. It's like if you walk into a room and have someone turn on the light for you instead of doing it yourself and then that person tells you the light is on or off. Here is the technical description of the QDM circuits.

Quad-Driver Modules (QDM) are used to control certain components in some engine management systems. When the ECM is commanding a component "ON," the QDM closes the switch completing the circuit to ground. Each QDM output has a sense 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 component "ON" and the voltage potential on a QDM "A" sense line is high, or if the component is commanded "OFF" and the voltage potential on a QDM "A" sensor line is low.

Either of these conditions will cause the QDM "A" fault line to display HIGH and set DTC 26. On all vehicles, the QDM "A" fault status on the scan tool will display HIGH with the brake applied or if the engine is not running. On vehicles with a 3T40 transmission, the QDM "A" fault status on the scan tool will read HIGH until the TCC in-line switch is closed. These conditions will not cause DTC 26 to set even though the fault line displays HIGH. To simulate driving in second gear and change the QDM status to low, disconnect TCC connector and connect a test light between harness terminals "A" and "D."

DTC 26 will set if:
  • The system is running in "CLOSED LOOP."
  • Brake switch is closed (brake not applied).
  • Transaxle in mid or high gear.
  • The ECM detects an improper voltage level on a QDM "A" controlled circuit for 10 seconds.

The ECM does not know which controlled circuit caused DTC 26, so each and every QDM circuit has to be tested to see which one caused the code to set.

Additional Information provided courtesy of ALLDATA

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