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2017 Buick LaCrosse - Intermittent No-Start & Security Light

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Paul Z. · rep 0 · May 22, 3:48 AM · 1 replies · solved · Question

Vehicle: 2017 Buick LaCrosse Premium

Hello Buick owners,

I'm having a frustrating issue with my 2017 Buick LaCrosse Premium, which has about 70,000 miles. Occasionally, it won't start. When I press the start button, all the dash lights come on, but the engine doesn't crank at all. Sometimes, the security light flashes or stays on during these no-start events.

After a few tries, or sometimes after waiting 10-15 minutes, it will suddenly start up perfectly fine, as if nothing was wrong. This is completely intermittent and unpredictable. I've checked the battery, and it seems good. Could this be an immobilizer issue, a faulty starter, or something with the key fob?

It's really concerning, especially when I'm out somewhere. Any ideas on what might be causing this or how to diagnose it?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:48 AM

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ClearTheCode admin answer:

An intermittent no-start condition combined with a flashing security light on your 2017 Buick LaCrosse points strongly towards an issue with the vehicle's anti-theft or immobilizer system, though other components can also contribute.

Here's a breakdown of potential causes and diagnostic steps:

  1. Key Fob Battery/Signal: Even if the dash lights come on, a weak key fob battery or interference can sometimes prevent the immobilizer from recognizing the key. Try using your spare key fob to see if the problem persists. Ensure the key fob battery is fresh.
  2. Immobilizer System: The security light is a key indicator. The vehicle's Body Control Module (BCM) or Engine Control Module (ECM) might not be receiving the correct signal from the key's transponder. This could be due to a faulty transponder in the key, a problem with the antenna ring around the ignition, or an issue with the BCM itself. A professional scan tool can often read specific immobilizer-related diagnostic trouble codes (DTCs) that generic OBD-II scanners might miss.
  3. Starter Motor/Solenoid: While the security light points elsewhere, an intermittent starter motor or solenoid can also cause a no-crank condition. If you hear a single click but no crank, it's often the starter solenoid. However, since you mention the security light, this is less likely to be the primary cause.
  4. Battery/Connections: Even if the battery seems good, ensure the terminals are clean and tight. A loose or corroded connection can cause intermittent power delivery, affecting sensitive electronics like the immobilizer.
  5. Ignition Switch (Push-Button Start): Though less common on newer vehicles, a faulty push-button start switch could intermittently fail to send the 'start' signal.

When to See a Shop:

  • If the issue persists after trying your spare key fob and checking battery connections.
  • If you cannot reliably start the vehicle, as this is a safety and reliability concern.
  • A dealership or specialized automotive locksmith will have the necessary diagnostic tools to properly read immobilizer codes and diagnose issues with the BCM, key programming, or antenna ring. These systems are complex and often require proprietary software for diagnosis and repair.
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