GMC Sierra Intermittent Starting Problem: Troubleshooting Guide for Frustrated Owners

You turn the key, and nothing happens. Or worse, your GMC Sierra started perfectly fine yesterday but today leaves you stranded in your driveway. If you’re dealing with the frustration of an intermittent starting problem in your GMC Sierra, you’re facing one of the most challenging issues to diagnose—but don’t worry, we’ve got you covered.

What Causes GMC Sierra Starting Problems?

When your Sierra decides to play the “sometimes I start, sometimes I don’t” game, the culprit usually hides in one of several key systems. Let’s break down the most common causes so you can get back on the road.

Faulty Starter Motor Issues

A failing starter motor tops the list of intermittent starting problems in GMC Sierras. You might hear a single click when turning the key while seeing all dashboard lights working normally. This happens when the starter solenoid engages but the motor fails to turn over the engine.

The problem often gets worse in specific conditions:

• After your truck sits in hot weather
• When the starter gets warm after multiple start attempts
• During cold mornings after sitting overnight

Many Sierra owners report that tapping the starter with a hammer sometimes temporarily fixes the issue—a classic sign of a starter that’s on its way out.

Electrical Connection Problems

Even with a perfectly good battery and starter, your Sierra might refuse to start due to poor electrical connections. These connection issues are incredibly common in GMC trucks and can be frustratingly intermittent.

Key areas to check:

• Battery terminals for corrosion (white or greenish powder)
• Loose battery cables
• The often-overlooked connection above the battery that’s notorious for developing poor contact
• Starter motor connections
• Ignition switch wiring

A simple cleaning of battery terminals with a wire brush and baking soda solution can often resolve what seems like a major starting issue.

Security System Malfunctions

If you’ve ever seen a “Service Theft Deterrent System” message on your dashboard, your GMC Sierra’s Passlock system might be the culprit behind your starting woes.

The security system in Sierra trucks is designed to prevent theft but often causes legitimate owners headaches when it malfunctions. The typical symptom is your truck starting briefly before shutting down immediately, or refusing to start altogether with a security light flashing on the dash.

A temporary workaround involves turning the key to the “ON” position (without starting) for about 10-12 minutes until the security light stops flashing, then attempting to start. For a permanent fix, you might need to have the Passlock system bypassed with a resistor or have the PCM reprogrammed to disable this overzealous security feature.

Ignition Control Module Failure

The ignition control module (ICM) in GMC Sierras often fails in a particularly frustrating way—intermittently. This module, responsible for generating the spark that ignites your fuel, typically fails due to heat sensitivity.

When this happens, your truck might:

• Start perfectly when cold
• Fail to restart after running for a while
• Have intermittent misfiring during operation
• Trigger a check engine light

The temperature-related nature of ICM failures explains why many Sierra owners report their trucks start fine in the morning but leave them stranded at the grocery store later in the day.

Fuel System Failures

When your GMC Sierra cranks but won’t start, fuel delivery issues might be to blame. Two components are particularly problematic:

1. Fuel Pump Control Module (FPCM)
Especially common in 2009 GMC Sierras, this module controls power to the fuel pump and is prone to failure. Located under the truck bed, it’s exposed to environmental elements that can cause intermittent operation.

2. Fuel Pump Problems
A failing fuel pump may work inconsistently, especially when your fuel level is low. Signs include:

• Engine stalling at highway speeds
• Difficulty starting after sitting
• Whining noises from the fuel tank area

To check if fuel delivery is your issue, turn the key to the “ON” position without starting. You should hear the fuel pump prime for about 2-3 seconds. No sound could indicate a fuel system problem.

Ground Connection Issues: The Hidden Culprit

One of the most overlooked causes of intermittent starting in GMC Sierras is poor ground connections. These critical electrical pathways can corrode or loosen over time, causing all sorts of electrical gremlins.

Critical Ground Points to Check

The ground system in your Sierra forms a complete circuit between the battery, engine, and chassis. When this circuit is compromised, electricity can’t flow properly, leading to starting problems.

Check these essential ground connections:

A quick visual inspection and cleaning of these grounds can often solve mysterious electrical problems that mechanics might spend hours trying to diagnose.

How to Test Ground Connections

1. With the engine off, use a multimeter set to ohms
2. Place one probe on the negative battery terminal
3. Touch the other probe to the engine block
4. You should see near-zero resistance (less than 0.5 ohms)
5. Repeat the test between the engine block and the chassis

High resistance readings indicate a poor ground connection that needs cleaning or repair.

Crankshaft Position Sensor Problems

The crankshaft position sensor tells your truck’s computer when to fire the spark plugs and inject fuel. When this sensor fails intermittently, it creates a particularly maddening starting problem.

Symptoms of a Failing Crankshaft Sensor

• Engine cranks but won’t start
• Starts sometimes but not others
• Stalling while driving
• Check engine light with specific trouble codes

What makes this problem so frustrating is that the sensor might work perfectly fine when cold but fail after heating up—or vice versa. This temperature sensitivity creates the classic intermittent problem that drives owners crazy.

Testing the Crankshaft Sensor

A professional mechanic can use an oscilloscope to monitor the sensor’s output signal during different operating conditions. Without specialized equipment, you can check for sensor-related trouble codes using an OBD-II scanner, which might show P0335 or P0336 codes for crankshaft sensor issues.

DIY Diagnostic Steps

Before heading to the mechanic, try these diagnostic steps to narrow down your GMC Sierra’s intermittent starting problem:

1. Basic Electrical System Check

Start with the simplest and most common causes:

1. Check battery voltage (should be 12.6V when resting)
2. Clean battery terminals thoroughly
3. Inspect all visible ground straps and connections
4. Try jump-starting when the problem occurs (if it starts with a jump, focus on battery/charging issues)

2. Starter Motor Testing

When the truck won’t start:

1. Listen carefully—do you hear a click, multiple clicks, or nothing?
2. Try tapping the starter with a hammer while someone turns the key (if this works, the starter is likely failing)
3. Check voltage at the starter during cranking (should be at least 9.5V)

3. Security System Bypass Test

If you suspect the Passlock system:

1. Turn the key to “ON” position (don’t crank)
2. Wait for security light to stop flashing (about 10 minutes)
3. Try starting the engine
4. If this works, consider a permanent bypass solution

4. Fuel System Quick Check

To verify fuel delivery:

1. Turn key to “ON” without starting
2. Listen for the fuel pump hum (2-3 seconds)
3. If no sound, check the fuel pump fuse and relay
4. Try spraying starting fluid into the intake (if it starts briefly, fuel delivery is likely the issue)

Common GMC Sierra Model Years with Starting Problems

While intermittent starting problems can affect any GMC Sierra, certain model years have shown more frequent issues:

The Comprehensive Approach to Fixing Starting Problems

Intermittent problems require patience and methodical troubleshooting. Follow this approach:

1. Document Everything

Keep a detailed log of when the problem occurs, including:

• Weather conditions (hot, cold, rainy)
• Time of day
• Whether the engine is cold or warm
• Any sounds you hear during starting attempts
• Any warning lights on the dashboard

This information can reveal patterns that point to specific components.

2. Start with the Basics, Then Go Deeper

Begin with simple checks:

1. Battery and connections
2. Starter motor operation
3. Ground connections
4. Security system function

If those don’t reveal the issue, move to more complex systems:

1. Fuel delivery components
2. Ignition system components
3. Engine sensors (crankshaft, camshaft position)
4. Computer and control modules

3. Use Specialized Testing When Needed

For truly stubborn problems, diagnostic equipment can help:

• OBD-II scanners reveal stored trouble codes
• Battery load testers confirm electrical system health
• Fuel pressure gauges verify proper fuel delivery
• Oscilloscopes can detect sensor signal problems

Sometimes the only way to catch an intermittent problem is to monitor the system over time with the right equipment.

Real-World Sierra Owner Experiences

Sierra owners consistently report that what seemed like major starting problems often turned out to be simple electrical issues:

“My 2018 Sierra had the dreaded click-no-start problem that would come and go. After two trips to the dealer, I finally found the issue myself—a loose connection above the battery. Tightened it up, and no problems since.”

Another common report involves the security system:

“Every few weeks, my 2015 Sierra would refuse to start, showing ‘Service Theft Deterrent System.’ After multiple dealer visits, I finally had the Passlock system bypassed completely. It’s been starting perfectly for two years now.”

GMC Sierra intermittent starting problems can be incredibly frustrating, but with systematic troubleshooting, you can identify and fix the issue. The good news is that most starting problems stem from relatively simple and inexpensive components rather than major engine or transmission issues. With patience and the right approach, you’ll have your Sierra starting reliably again.