Snap-on scan tool 2001 one ton Chevy truck?

Question

I am trying to break into the 20th century and bought a scan tool. On a 01 Chevy ser# 1GBJC34U21E262315 , throttle cable ,non Calf. emissions the check engine light is on and sometimes flashing [misfire may ruin cat.con.] and has the folowing codes; PO137,PO140,PO154.PO157,PO160& PO3OO.
Code tips say B1 S1 - 02 Sensor and B2 S1 - 02 senser. Dose this mean Bank 1 Senser 1and Bank 2 Sensor 1? The voltage from These 02s is up & down from apx 50-800 changing very rapidly. B1 S2 & B2 S2 are steady. Is the S1 the pre cat 02 and S2 the after cat 02?
Is there a easy test for 02 sensers?
How do I tell if it is in closed loop?
What is the 4 red lights on scan tool for?
The scaner is the small red retangle box with scrowl Knob.
Thanks

Answer 1

That pretty much is the test. The sensors give erratic readings when the get old. Don't worry about anything else till you replace them, clear the codes and drive it for a few days. Make sure the connectors for the sensors are nice and tight too.

Answer 2

1. Check the engine oil level Assuming that the oil level is correct and the light still blinks. Is it blinking only at idle? If so, is the idle speed correct? Assuming that it is at idle only and the idle speed is correct. Try a heavier oil (if you're using 5w 30 try 20w 50) If it blinks at driving speeds, it could be: Faulty oil pressure sensor Worn out oil pump and/or main and rod bearings. Clogged filter or sump screen. It could also be contamination of the oil with fuel (does the oil smell like gas?) In any case, start with an oil change.