Originally Posted by jr's3800
Looking at the 1995 service manual( 1994 and 1995 use the same PCM) The book says that 1640 is Quad Driver Module #1 Circuit which controls The Boost Control solenoid, Evap Purge Canister and the TCC Apply Solenoid... So there may be a problem in one of these areas...
Don't go replace parts just yet.... Someone with a 1994 Service manual, or a Gearhead jump in and give some thoughts here
The QDM primary function is to supply ground to the item being controlled, and it has a fault-detection circuit. It will set 1640 when:
The engine is running.
The PCM detects an improper voltage on a circuit connected to the QDM
The above conditions last for at least 5 seconds.
The solenoids under control are the Boost control, the Evap Purge, and the Traction-control-apply (inside transaxle)
Since your symptoms seem to apply to ALL solenoids, the problem is almost surely with the PCM or the connections to the PCM. Otherwise, you would only have the symptom associated with the affected solenoid, such as low boost if its the boost control, dies if its the evap purge, and no TCC if its the Traction control.
You may also want to check the cruise-control fuse, 15 amp, and the 10 amp cooling fan/TCC fuse, if you haven't already dones so. They appear to be part of the overall circuitry, supplying the "plus" power to these 3 solenoids.
(The cruise control fuse is said to be in the relay centre, and the 10 amp cooling fan/tcc fuse is in the fuse block.)