Car has been running fine lately, no problems. All of a sudden, check engine light comes on while driving, no noticeable difference on highway/local road. However, the difference is apparent when the car is at a red light or in park idling.

Codes read back are 3-2-1, 2-2-3, 1-2-2, 1-2-1. I have a regina system. These codes correspond to:

3-2-1 Signal missing to/from cold start valve
Source of fault: Radio suppression relay
2-2-3 Signal missing to/from idle valve
Source of fault: IAC Idle air control valve
1-2-1 Signal missing or faulty to/from pressure sensor
Source of fault: MAP Pressure sensor
1-2-2 Signal missing or faulty to/from air temperature sensor
Source of fault: Air temperature sensor

Okay... too many things are supposed to be broken at once. Did something in my wiring just die? Wiring harness? I tried disconnecting and reocnnecting the connectors for each of those sensors. They appear clean and snug, and it's doubtful they all just decided to lose contact simultaneously.

Any suggestions are greatly appreciated, thanks!
--
Ken
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'