How about P1670? 0670 doesn't exist.
P1670 QDM4 according to the 95 FSM:
Will set when:
Engine is running
PCM detets improper voltage level on a circuit connected to QDM4
Above conditions are met for 5 seconds
Your 4 suspects are:
MIL (service engine soon light)
Low speed fan relay
High speed fan relay
If your MIL (SES) light comes on when it should, rule that out.
Is your AC working?
Do your fans work on high speed when the AC is on?
Does your low speed fan run when it shouldn't?