27 (1993-1994 Vehicles) Quick Quad Driver Output Fault
Notice: Refer to TSB# 96-T-08 for updated information.
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 turned 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.
- 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.
- EGR Solenoid: . . . . . . . . . . . 20 - 50 Ohms
- EVAP Canister Purge Solenoid: . 20 - 50 Ohms
- Coolant Fan Relay: . . . . . . . . 7O - 90 Ohms
- A/C Relay: . . . . . . . . . . . . . 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 a 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 way the fault detection logic works. For example. if the EGR solenoid is off, the PCM expects to see 12 volts on the sense line. If the circuit is open, 0 volts will bee 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 will not detect a fault. In this example, the display 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 circuit 817 to passive restraint module for an open or short to ground.