OK so I have an 02 bonneville sle...I recently had the catalytic converter replaced and while I pulled the codes for that I also got the code for the mass air senor..And The car has been running slightly rough it has a hic up when you drive it occasionally and the light comes off and on when it pleases...I took the mass air sensor out and cleaned and inspected it it looked ok but still having isssues...Also just last night I went out with some friends and it ran fine, but when we went to head home the car wouldn't start the battery cables are ok and if you just turn the key on you can watch the voltage drop....But once it starts it runs fine... Once you get it started the voltage reads normal and you can turn it off and start it again no problem but if you leave it sit for awhile it seems like its a weak start...Any ideas would be appreciated..

Thanks

IF the cables are good then I'd say it'* a weak battery. Needs replacing. That'* exactly what my battery was doing before I replaced it.

Check the battery cables for corrosion and check your ICM for corrosion. Load test the battery and replace if necessary.