Just changed the battery in my 2014 GMC Sierra 1500 and the alarm system started, lights flashing, alarm sounding. Remote entry won’t work.

SOURCE: Dodge ram 1500 will not start, battery will not

Check the starter motor, the starter solenoid and if it's automatic... the neutral safety switch.
If it's standard, the clutch has a switch which locks out the starter unless completely depressed. Check the switch for continuity.

SOURCE: 2006 gmc sierra 1500 stalled and will not start.

i have a 06 sierra that done the same thing and it was the distributer gear stripped

SOURCE: flashing alarm light after battery change. Car wont start,

System operation
System arms 5 seconds after switching ignition OFF. Switch ignition ON. Ensure clock LED illuminates for 3-5 seconds. If LED flashes rapidly at regular intervals for approximately 1 minute, then flashes at irregular intervals: Key code not recognised. Remove key and try again.
Programming
When
System malfunction: LED illuminates for 1 minute, then flashes at irregular intervals. Key(s) added or replaced.
NOTE: Replacement keys MUST have blue mark. Keys with red mark are NOT compatible with this system.
How
NOTE: Programming method using vehicle keys can be deactivated using diagnostic equipment.
Obtain 2 programmed keys (A and B). Insert key A into ignition switch. Turn ignition switch to position II. Wait 1 second. Switch ignition OFF. Remove key A. Insert key B into ignition switch within 5 seconds. Turn ignition switch to position II. Wait 1 second. Switch ignition OFF. Remove key B. Within 10 seconds: Insert key to be programmed into ignition switch. Turn ignition switch to position II. Wait 4 seconds. Switch ignition OFF. Wait 5 seconds. Start engine. If engine does not start and clock LED flashes: Switch ignition ON. Wait at least 20 seconds. Switch ignition OFF. Repeat programming procedure. Repeat above procedure to program remaining keys. Keys can also be programmed using diagnostic equipment

SOURCE: LOW OIL PRESSURE ON 2007 GMC SIERRA 1500. CHANGED

have it tested using a manual gage if still low then main baring ore most likely bad that would mean a over hall if is really low and bearings bad should be making rattle noise when started up first few seconds

Testimonial: "thanks alot.truck is not making a rattling noise.we did check it with a manual gauge.it read about 10 at idol. press. gets better as you incr speed"

SOURCE: 2007 GMC YUKON. Keyless Entry problem. The remote ...

Disconnect the battery to the car for five mins. Thay should reset the keyless module. I had the same problem