1991 C-1500 Service engine light is on. But O'Reilys can not read any codes. Lighter fuse is good

SOURCE: Code reader failure/cigarette lighter fuse

no check. all fuses w/a test light on both sides

SOURCE: 2003 Buick Regal Service Engine Soon light.

The error that I'm showing for error code P1133 is 
P1133 Heated Oxygen Sensor (HO2S) insufficient switching bank 1 sensor 1(Rear Bank).  I would suggest having both of your Oxygen Sensors replaced if you haven't already had that done.  Hope this helps.  Thanks for an honest rating and for using FixYa.

SOURCE: service engine soon light came on. AutoZone read

Sometimes you have to wait a week for the light to go off, the computer has to go through several start/run/stop cycles.

SOURCE: Check engine light codes reads 16683

16683/P0299/000665 - Boost Pressure Regulation: Control Range Not Reached Possible Symptoms

• Reduced Power Output
• Limp Mode

• Hoses/Pipes incorrect connected, disconnected or leaking
• Charger Pressure Control defective

• Check Hoses/Pipes to/between Components
• Check / Clean / Replace Charge Pressure Control

• When found in 2.0l TFSI:
  • Check Boost Pressure Control Valve (N249), for cracked rubber diaphragm. A new/optimized Valve is available under Part # 06F-145-710-G (or newer), see TPI 2016331 for details.

SOURCE: engine light on code reads po401

I believe this code is insufficient EGR flow. On this engine, the passages to the EGR valve often become carboned up and cause this code. Remove the EGR valve and inspect the passages to see if they need to be cleaned.