1994 Pont. Transport has trouble code P1640 QDM 1. It's control module circuit A. Can anyone explain this in English so I will know where to look.AC compressor started squelling last week and needs replacing, can this have anything to dowith code. Haynes manuals useless.

Hi,

Any symtoms?
I had this code together with other malfunctions.
Turned out to be the ignition switch.

Andy

No symptoms at all. Ignition switch was new last year. Only thing different was the AC pulley bearing noise.

Well, problem solved. Turned out that when the AC compressor bearing seized there was an overload on that circuit. Everytime car was started there was a heavy draw on the ac power circuit and it just wanted help. Changed AC compressor (pain), reset check engine light, no more trouble. Andy, thanks for answering.