Originally Posted by Cynical1x3
Another symptom is that (in park). the car will rev to about 4000 RPM then go back down to 3000. It won"t rev past 4000.
There is a rev limiter at 4000 RPM if the car is going less than 15 MPH. That part is normal.
However, on most OBD 1.5 (like yours), P1640 seems to indicate that Quad Driver Module 1 is on the fritz. Here'* one thread about it
; you can search for "P1640" and find many more.