Pontiac g6 runs lean; throwing codes

Having a lean condition isn't good for the motor.

Lean is higher oxygen and lower fuel. Oxygen burns hotter than fuel. Being lean is to have a condition where the fire in your engine is hotter. The results are increased wear on valves and potentially melting the aluminum of the head. The melting is under extreme conditions.

You are in a situation where the ECU has essentially set itself into a 'safe mode' of pre-programmed settings if it feels the data it's receiving from various sensors is questionable.

The 0073 code, IMO, is the key. This is a failed bus on the ECU if I'm correct. You can try getting a used ECU on ebay or another source of used equipment or replacing with OEM. Validate what I've said, ECU's are expensive.

Best of luck.

PS. Too many variables on the ABS. If your front tires are over worn, it can act up under hard braking and give the steering wheel a good shake. Validate tire tread depth and brake pads as a starting point on the ABS issue.

Yes, it's serious. It's usually either because your MAF sensor is dirty, or one or more fuel injectors aren't working properly. Check out this link. You should still be able to drive a car that's running too lean, but you should never, under any circumstances drive it fast or put it under heavy load.

From the link

Causes

• A code P0171 may mean that one or more of the following has happened: The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
• There could be a vacuum leak downstream of the MAF sensor
• Possible cracked vacuum or PCV line/connection
• Faulty or stuck open PCV valve
• Failed or faulty oxygen sensor (bank 1, sensor 1) Sticking/plugged or
• failed fuel injector Low fuel pressure (possible plugged/dirty fuel filter!) Exhaust leak between engine and first oxygen sensor

Possible solutions:

• A lot of times, cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. If you're on a tight budget, start there, but that may not be the fix for certain. So, possible solutions include:
• Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
• Inspect all vacuum and PCV hoses, replace/repair as required
• Inspect all hoses and connections in the air intake system
• Inspect and/or test the intake manifold gaskets for leakage
• Check for a dirty fuel filter and proper fuel pressure
• Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool
• If you have access, you may want to run a smoke test

The fuel system and throttle body were dirty. I flushed Seafoam through via the oil, gas tank, and vacuum line. I also cleaned the throttle body, and the engine runs/idles perfectly clean.

had p0171 and p0174 codes, cleaned the maf sensor and replaced air filter that was not previously installed right and seems to have taken care of the problem.