why does my GMC Sierra T1XX (2019-Present) have a hard time starting in the morning?

Learn how to diagnose and fix hard starting issues in GMC Sierra T1XX (2019-Present). Step-by-step guide with symptoms, diagnostic steps, and repair instructions.

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, socket set, fuel pressure gauge, and safety glasses.
• Ensure the vehicle is parked on a flat surface and the engine is off.
• Disconnect the negative battery terminal to avoid electrical shorts.

2. Battery Inspection and Replacement

• Inspect Battery:
  • Clean battery terminals with a wire brush and apply anti-corrosion spray.
  • If battery voltage is below 12.4 volts, proceed to replace the battery.
• Replace Battery:
  • Remove the negative terminal first, followed by the positive terminal.
  • Unscrew and remove the battery hold-down bracket.
  • Lift the old battery out and place the new battery in the tray.
  • Reinstall the hold-down bracket and connect the positive terminal first, then the negative terminal.
  • Torque battery terminals to manufacturer specifications (typically 10-15 ft-lbs).

3. Fuel System Check

• Inspect Fuel Pump:
  • Turn on the ignition to the "on" position without starting the engine.
  • Listen for the fuel pump; it should run for a few seconds. If not, check the fuel pump fuse and relay.
• Test Fuel Pressure:
  • Connect the fuel pressure gauge to the fuel rail test port.
  • Start the engine and observe the gauge for proper pressure (usually between 55-62 psi for GMC Sierra).
  • If pressure is low, replace the fuel pump as necessary.

4. Starter Inspection and Replacement

• Inspect Starter:
  • Check for any loose connections at the starter and ensure proper grounding.
  • If the starter is not engaging properly, remove it for further inspection.
• Replace Starter:
  • Disconnect the negative battery terminal again.
  • Remove wiring harness connectors and bolts securing the starter.
  • Install the new starter, ensuring all connections are tight.
  • Reconnect the negative battery terminal.