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2021 Ascent "Key Not Detected" - Won't Start

0

Steve N. · rep 0 · May 22, 3:18 AM · 1 replies · solved · Question

Vehicle: 2021 Subaru Ascent Touring

Hi everyone,

I'm having a major problem with my 2021 Subaru Ascent Touring. This morning, I got into the car, pressed the start button, and it just kept saying "Key Not Detected" on the dash. The car won't start at all.

I immediately thought it was the key fob battery, so I replaced it with a brand new one, but the message is still there, and the car still won't start. I tried both of my key fobs, and neither works. The doors unlock and lock fine with the fob buttons, so it seems like the fob itself has some power.

Has anyone else experienced this with their Ascent? What could be causing this? It's really frustrating not being able to start my car.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:18 AM

0

ClearTheCode admin answer:

The "Key Not Detected" message on your 2021 Subaru Ascent Touring, especially when both key fobs are failing and their batteries have been replaced, points to an issue with the vehicle's immobilizer system or the key fob's communication with the car.

Common Causes:

  1. Weak Key Fob Battery (Even New Ones): Sometimes, new batteries can be faulty or low on charge. It's worth trying another fresh battery from a different pack.
  2. Key Fob Signal Interference: Other electronic devices, strong radio signals, or even large metal objects can interfere with the key fob's signal.
  3. Vehicle's 12V Battery: A weak or dying car battery can cause various electrical gremlins, including issues with the key detection system, even if other functions like door locks still work.
  4. Immobilizer System Malfunction: The car's immobilizer antenna (often located around the ignition button) or the immobilizer control unit itself could be faulty.
  5. Key Fob Malfunction: Although less likely if both fobs fail, one or both fobs could be faulty.

Troubleshooting Steps:

  1. Emergency Start Procedure: Subaru vehicles with push-button start often have an emergency start procedure. Hold the key fob directly against the start button while pressing the brake pedal and attempting to start the car. This uses an RFID chip in the fob for direct communication, bypassing the wireless signal.
  2. Check Car Battery: Use a multimeter to check the voltage of your Ascent's 12V battery. A reading below 12.4V could indicate a weak battery that needs charging or replacement.
  3. Try in a Different Location: Move your vehicle to a different spot, away from potential sources of electronic interference, and try starting it again.
  4. Inspect Fob Battery Orientation: Double-check that the new key fob batteries are inserted with the correct polarity.

When to See a Shop:

If the emergency start procedure fails, your car battery is confirmed to be good, and you've tried all other troubleshooting steps, it's crucial to have your Ascent towed to a Subaru dealership. They have specialized diagnostic tools to read codes from the immobilizer system (B-codes) and can accurately diagnose whether the issue is with the key fobs, the immobilizer antenna, the control module, or another electrical component. This is a safety-critical system, so professional diagnosis is essential.

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