Cranks but will not start.

Probably better off with a mechanic. "Just cranks and nothing". What does that mean? I assume you mean the engine cranks but doesn't start and run, but when I make assumptions I'm usually wrong.

There can be more than one diagnostic fault code stored so just because you already know of one for one of the oxygen sensors, they should still be read to see if there's other codes related to the problem.

The oil warning light is for low oil pressure, not level. There won't be any oil pressure if the engine doesn't run so that light had better be on. That is not a clue to this problem.

The generator recharges the battery and runs the car's electrical systems when the engine is running. It has nothing to do with a no-start condition.

You already said the engine cranks so why would you be questioning the starter?

Start by having the codes read to see if there's anything related to the problem you're having. Keep in mind those codes never say to replace parts. They only indicate the circuit or system that needs further diagnosis. It is often more cost-effective to visit a mechanic, especially for those of us who install numerous parts to try to solve a problem.

Just to add to this one does the gas gauge work fuel gauge work power door locks keyless entry work etc if you have thlse options?Also the security light on solid or flashing?I would also check for codes like cardiodoc said. Those cars have a high failure rate on there body control modules causing no starts. You could could also check for spark I have seen some bad crank sensors on those.

Thanks saturntech9. One thing I forgot to mention is all fault codes on all car brands have a list of things that must be met to set that code and one of those things is almost always that certain other codes are not already set. The Engine Computer compares sensor readings and operating conditions to each other to figure out when one of them is wrong. If there's a code set already, the computer knows it can't trust certain sensor readings so it won't run tests on other circuits that use the defective readings to compare to. That means you could get a code related to this problem only after you fix the cause of the oxygen sensor code and erase it.

You never answered the questions I asked you in my last post?Also have you checked for spark yet?

I gather repair 1 & 2 did nothing and repair 3 the BCM did for sometime? So they will replace the BCM no charge? If I have the facts correct then let them replace BCM. Which would have been a better repair # 1
Hope this helps

The amperage to work the lights ect. Is small comepared to the 175 to 225 amps needed to start the car. Get someone to jump start if it fires have batt and alt checked.
Good luck

So it will turn over and not start first thing in the morning? Or it doesnt turn over? Your post confused me on what is happening. If it turns andwont start, have the fuel pressure tested, could bea pump bleeding down pressure overnight and it takes it a litte bit to build it back up.

One more time. When you say "wont start" do you mean wont crank, or wont actually start? If the pump bleeds down, it will trap air in the lines and it takes a littel bit of cranking to build the pressure back up and drive the air out. Does the security light blink when it wont start?

Have you done a relearn on the pass-key?
GM PASS LOCK RELEARN- Ignition to "run" position, try to start and let key return to "run" position
Approx ten minutes security light will go off
Turn key "off" and wait 5 seconds
Repeat 2 more times for a total of 3 relearns.
Turn key off, then start it
I'm pretty sur this is Jack's advice on this one?