Powertrain Controls - ECM/PCM

QUICK QUAD DRIVER OUTPUT FAULT

A quad driver module is a semiconductor device capable of controlling four separate outputs. Each output of the QDM is an open collector driver which when turn on pulls the output to ground. A load is connected between 12 volts and the driver. When the output is turned on, current flows from the battery, through the load, through the driver to ground. Each QDM has a fault line feedback. A comparison of the driver input and output states is performed. If the input and output are in the same state, a fault will be detected. Each QDM has only one fault line that will detect a fault on any of the four outputs.

INFORMATION FLAG PARAMETERS

Information flag 27 will set if:

There is an open or short on any of the QDM output circuits. Fault is detected for 5 seconds.

DIAGNOSTIC AIDS

^ DTC 27 is used to aid in finding the problem area with an intermittent circuit.

^ If any corresponding codes have been set (example DTC 32) diagnose that QDM first.

^ If only quick QDM 27 is set, this indicates an intermittent problem. Carefully check the tightness of the female terminal grips with the spare male terminal.

Components Resistances:

^ EGR Solenoid 37-44 ohms

^ Evaporative Canister Purge Solenoid 22-42 ohms

^ Coolant Fan Relay 70-90 ohms

^ A/C 70-90 ohms

^ A shorted or open solenoid, relay or bulb can cause a DTC 27.

^ If any corresponding codes have been set (example DTC 32) diagnose that QDM circuit first.

^ When viewing "QDM FAULT" (using scan tool or Dynamic Display), you may notice the fault appears to be intermittent. This may be due to it being an intermittent fault, but more likely is due to the fault detection logic works. For example, if the EGR solenoid is off, the PCM expect to see 12 volts on the sense line. If the circuit is open, 0 volts will be seen, and the fault will be displayed. However, if the EGR solenoid is turned on (for instance at cruising speeds) the PCM expects to see 0 volts on the sense line, and would show "QDM FAULT A" at idle, but if the RPM is raised, the display will show "QDM FAULT NONE." When returned to idle, the fault will again be displayed.

^ Use service stall system (if available) to diagnose the quad driver circuits.

^ Check circuits 817 to passive restraint module for an open short to ground.