computer codes

I need some assistance with my 94 transport. Check engine light is on. Checked it with my ez-scan, and got 2 codes. QDM1 and QDM4. I know that this means quad driver module, but on this OBD-1 system, how can I determine which sensors or whatever is malfunctioning? Any help is appreciated.

Quad drivers are "output" circuits: they trig something on or off, like transmission solenoids, TCC solenoid or EGR valve (check this out www.avigex.ca/xport/dtc56.jpg
this is for '93 not with linear EGR used in 94 however).
www.avigex.ca/xport/dtc26.jpg
The quad circuit itself is short protected so this code means the trigged device is not connected, blown out or shorted. Hence you should notice the effect in the way the car behaves, like no TCC or the like.

Quad drivers are "output" circuits: they trig something on or off, like transmission solenoids, TCC solenoid or EGR valve (check this out www.avigex.ca/xport/dtc56.jpg
this is for '93 not with linear EGR used in 94 however).
www.avigex.ca/xport/dtc26.jpg
The quad circuit itself is short protected so this code means the trigged device is not connected, blown out or shorted. Hence you should notice the effect in the way the car behaves, like no TCC or the like.
I have noticed that the TCC kicks out after reaching normal operating temperature on the engine temp gauge, so thank you for the information. Now I will just have to break out my testers and see what I can find.