Saturn Coupes/Sedans/Wagons 1991-1998 Repair Guide

Quad Driver Module (QDM)



The Powertrain Control Module (PCM) operates its output devices, such as solenoid valves, relays and indicator lights, by commanding a driver module. A driver module is an electronic switch that turns ON to complete the ground circuit and operate the 12 volt device. A Quad Driver Module operates 4 electronic switches for 4 output devices. There are 2 QDMs in the PCM. Each has a feedback circuit that detects an open or short circuit on an output device that it controls.


See Figure 1

  1. All relays should have 70-90 ohms resistance. All solenoids should have 22-42 ohms resistance.
  3. Turn the ignition switch ON and watch the lights on the instrument panel. The SERVICE ENGINE SOON and coolant temperature lights should turn ON , then the coolant temperature light should go out. If not, check the fuses, bulbs and ground circuits.
  5. Jumper terminals A and B on the ALDL. The cooling fan on the radiator should run.
  7. Remove the jumper wire, then start the engine and operate the vehicle as required to test the remaining components.

Click image to see an enlarged view

Fig. Fig. 1: Schematic for the PCM quad driver circuits