Key Fob Won’t Open or Start Car

If your fob won’t unlock the doors or the car stays dead silent when you press start, odds are the car and the fob aren’t talking to each other.

Why It Happens

Your fob isn’t just a remote—it’s a digital handshake device. When you press unlock or push the start button, the fob shoots out a coded signal. The car’s computer listens, checks it against its memory, and only if it matches will it unlock or fire the engine.

If nothing happens, that handshake is broken.

Most Common Causes

• Dead fob battery – the most common, cheapest fix.
• Damaged or drowned fob – chips inside can fail if dropped or water-soaked.
• Signal interference – other electronics or keys bunching together can block the handshake.
• Faulty receiver in the car – the antenna around the ignition barrel or push-button sensor isn’t picking up the signal.
• Low car battery voltage – modern immobilisers won’t even attempt if supply is weak.

Opening the Car

First things first — you need to get into the car.

Once you’re inside, you can move on to starting checks.

Quick Checks You Can Try

1 Use the spare fob. If it works, you’ve nailed the culprit.

2 Press the fob directly to the start button. Many cars have a hidden “hot spot” backup reader—look for a symbol near the column, console, or cupholder.

3 Separate the fob. Keep the fob clear. Big keychains, other electronics, even those flashy ring trims around the ignition or start button can mess with the signal.

What a Mechanic Will Check

• Scan for fault codes (“Key Not Recognised,” “Immobiliser Error”).
• Test the fob on a key-programming machine.
• Check the car’s antenna coil for signal and wiring integrity.
• Inspect immobiliser and ECU communication.
• Reprogram or replace the key/fob if necessary.

Ballpark Repair Costs

• Fob battery: $5–$15
• Spare key/fob programming: $80–$250
• Reader coil replacement: $120–$250
• Immobiliser/ECU repair or replacement: $400–$900+ (dealer/locksmith job)
• Car battery replacement: $120–$200

When to Call It Quits

If the spare fob doesn’t work and the immobiliser still won’t play ball, you’re out of driveway-fix territory. At this point you’ll need a scan tool, a locksmith, or a trip to the dealer.