When a car unlocks but refuses to start, it usually points to a problem with the key’s recognition system. This issue catches people off guard, especially if the fob worked seconds earlier. Today’s cars rely on built-in electronic verification between the key and the ignition system. If that link fails, your engine stays quiet. We’ve seen this happen often, especially during colder months or after battery changes. Our goal here is to help you figure out what’s going wrong and what to do next so you can get moving again without frustration or confusion.
Start with Checking the Fob’s Battery
Most times, a weak or dying battery in the key fob causes the failure to start. The car might still detect the fob enough to unlock the doors, but starting the engine takes a stronger signal. That is to say, the ignition system needs more consistent communication with the chip.
Many modern cars have push-to-start systems that rely heavily on the signal from the fob. If the battery voltage drops even slightly, the system might not respond. We always suggest replacing the fob battery as your first step. It’s cheap, quick, and often solves the issue.
Look in the manual to find the correct battery type. Use a clean, dry surface when opening the fob case and avoid touching the chip directly. Even a slight misalignment after replacing the battery can affect signal strength.
Try the Backup Start Method
Some vehicles come with a backup process to start the engine even when the fob signal fails. For instance, there may be a marked spot where you can press the fob against the push button or insert it into a hidden slot near the dashboard.
These emergency start procedures vary by vehicle. Therefore, it’s a good idea to check your manual or contact your dealer to confirm your model’s method. Once you locate that area, hold the fob firmly against it while pressing the brake and ignition button.
If it starts, that confirms the key is still paired correctly but the battery is weak. That makes battery replacement your next step. However, if nothing happens, you may have a deeper programming or signal problem.
Look for Key Error Messages on the Dash
Next, turn your attention to the dashboard. Many vehicles display warning lights or text if they fail to recognize the key. Messages like “Key Not Detected” or “No Key” offer clues about the issue.
A “Key Not Detected” message usually means the car’s receiver isn’t getting a strong enough signal from your key. That could be caused by a drained fob battery, physical damage, or even interference from nearby devices.
If you see “Invalid Key” or something similar, that points to a programming issue or a corrupted chip. In those cases, no amount of battery swapping will help. You’ll need help from an automotive locksmith in Ottawa to reprogram or replace the fob.
We’ve handled cases where the key itself was still working, but the chip was partially damaged after water exposure. These failures don’t always appear right away, but they show up when the car demands full communication during startup.
Move the Key Closer to the Ignition Zone
Sometimes, the key fob’s signal just needs a boost. That happens more often in vehicles with poor signal shielding or in places with strong wireless interference. You might notice that the car unlocks when you’re nearby, but it fails to start once you’re inside.
Try placing the fob as close as possible to the ignition sensor. In some models, the sensor sits behind the push-button start or under the steering column. Hold the fob near that zone while pressing the start button.
Do this with your phone and any other wireless devices away from the fob. Interference from Bluetooth or Wi-Fi signals can confuse the system. If the car starts after moving the key, you’ve likely found a weak signal area in your cabin.
Inspect the Key for Physical or Water Damage
Keys that seem fine on the outside can hide internal damage. We’ve seen people continue using key fobs after dropping them in water or snow, only to find out the circuit board failed days later. Moisture can damage the transponder chip even if the battery works fine.
If your car unlocks but refuses to start, and you’ve ruled out the battery, inspect the fob shell. Look for signs of cracks, moisture inside, or loose buttons. A small rattle sound when you shake the key often means loose solder joints or corrosion.
Even if the key still opens the car, it might not transmit the start code correctly. In this case, you’ll need help from a locksmith in Ottawa with tools to test the chip and clone or replace it safely.
Some drivers try to dry out fobs in rice or leave them in the sun, but that rarely restores chip-level issues. The best option is testing the key with a professional device to confirm whether the transponder still responds properly.
Use a Spare Key If Available
If you have a backup key, now’s the time to use it. Switching to a different key can help you figure out whether the issue lies with the car or just the original fob. If the spare starts the car without issue, that confirms a key-specific failure.
It’s important to store backup keys outside the vehicle, especially in cold climates. That prevents both keys from facing damage at the same time. We’ve seen drivers store both keys in the same jacket or glovebox, only to realize both fobs had dead batteries.
Once the spare works, avoid using the failed fob again until it’s tested. Continuing to use a failing key could lead to full lockout or make future reprogramming harder. If neither key works, that points to a receiver issue in the vehicle itself.
Scan the Vehicle for Receiver Errors
There’s also a chance that the problem doesn’t come from the key at all. In rare cases, the car’s receiver module fails. That module is responsible for detecting the fob and confirming its code before allowing the engine to start.
If both keys stop working, or you suddenly need to hold the key closer each time, this part might be to blame. Receivers can fail after water exposure or voltage issues from other parts like the battery or fuse box.
These issues require a professional scan tool to identify. Local shops might not have the right software to test the immobilizer system. You’ll need help from someone who understands both key programming and ignition module behavior.
In many cases, our team at True Fix Locksmith Ottawa is called when people believe the problem is with their fob, only to discover the receiver failed after a battery change or short circuit. Early diagnosis saves time and unnecessary reprogramming.
Contact a Locksmith for Diagnostic Help
Once you’ve tried the above and the car still won’t start, it’s time to speak with a professional. When you contact an expert who specializes in vehicle access systems, they can quickly tell whether the issue comes from the fob, the ignition, or the vehicle’s computer.
Unlike dealerships, mobile locksmiths can test the key and vehicle on the spot. That avoids towing fees and long delays. They use tools that detect fob frequency, read stored faults, and reprogram or replace the key right there if needed.
If you’re stuck, don’t wait. Get in touch with us to speak with someone who handles key recognition issues daily. We can help figure out what’s wrong and get your car started again safely and quickly.
FAQ
Why does my car unlock but not start with the key fob?
The fob might have a weak battery or signal issue. It can still unlock the doors with low power, but it needs a stronger signal to start the car.
Can cold weather cause the key not to be recognized?
Yes, extreme cold can weaken the battery inside the key fob or interfere with signal transmission to the ignition system.
Is replacing the key fob always necessary?
No, sometimes just replacing the battery or resetting the signal by holding the key near the ignition is enough to fix the issue.
What should I do if both my keys stop working?
This often points to a problem with the vehicle’s receiver. You’ll need diagnostic help to identify the failed part and fix it.
Can I start the car without a working key fob signal?
Some cars allow emergency starts using a backup method. Check the manual or try placing the fob directly on the start button.