Remote start failures have multiple possible causes. This guide walks through diagnosis from the simple (fob battery, hood switch) to the more complex (programming, module failure).
Remote start is one of the most appreciated features in Georgia's hot summers -- starting the car and running the air conditioning before you get in is a practical comfort advantage that drivers quickly come to rely on. When remote start stops working, it can feel disproportionately frustrating given how simple the feature is in daily use. The diagnostic path depends significantly on what type of remote start system your vehicle has and what exactly is failing.
Vehicles with factory remote start (installed by the manufacturer, operated through the key fob) and aftermarket remote start systems (installed after purchase, operated through a separate fob or smartphone app) have different failure modes and different repair approaches. This guide covers both.
Possible Causes
Key fob battery weak or dead
Very Common
The remote start button on a standard fob requires the same battery as the other buttons. A dying battery may cause loss of remote start range before other functions are affected.
Hood pin switch triggered
Common
Remote start systems disable themselves when the hood is open (safety feature). A faulty or misaligned hood pin switch can falsely signal 'hood open' and disable remote start even when the hood is fully closed.
Door ajar or trunk open
Common
Most remote start systems disable when a door, hood, or trunk sensor reports as open. A faulty door ajar sensor can prevent remote start.
Vehicle needs service (check engine light, low brake fluid, etc.)
Moderate
Many factory remote start systems are programmed to disable when the vehicle has active fault codes, low fluid levels, or other conditions requiring service.
Aftermarket system programming fault
Moderate for aftermarket systems
Aftermarket remote start modules can lose their programming to the vehicle's immobilizer, particularly after battery disconnection or firmware updates.
Step 1: The Basics
Before any technical diagnosis, confirm the basics. Replace the key fob battery with a fresh name-brand battery. This is the single most common cause of remote start failure and costs under two dollars. Install the new battery, test lock/unlock (which should work), then test remote start. If remote start is restored, you are done.
If the fob's lock and unlock buttons work normally but only remote start fails, the battery is not the issue -- remote start typically requires slightly more range or more button presses (usually pressing and holding the start button for 2+ seconds) than lock/unlock. Make sure you are within functional range and pressing the button with the correct duration.
Check whether the remote start requires a specific sequence. Factory remote start systems vary in activation sequence: some require pressing the lock button first, then holding the start button; some require pressing start twice; some require a specific button combination. Consult the owner's manual for your specific vehicle's remote start activation sequence to ensure you are not triggering the wrong procedure.
Step 2: Check the Hood Switch
The hood pin switch is a small switch positioned where the hood meets the body, typically at the front corners or center of the hood opening. When the hood is open, this switch tells the remote start system that the engine bay is accessible -- a safety feature to prevent injury to someone working under the hood. If the hood pin switch fails, corrodes, or gets misaligned, it can falsely signal an open hood and permanently disable remote start.
To check the hood switch: open and fully close the hood, ensuring it latches firmly. If remote start remains disabled and you can see the hood pin switch (typically a small black button or plunger at the front edge of the engine bay), press it manually with your finger while trying remote start. If the system activates, the switch is misaligned or sticky and needs adjustment or replacement.
Hood pin switch replacement or adjustment is a minor repair that most shops can perform quickly. For most domestic vehicles, the switch is an inexpensive component. For vehicles with aftermarket remote start systems, the switch may be part of the aftermarket kit and may require the installing shop to adjust.
Aftermarket Remote Start Systems
Aftermarket remote start systems (Compustar, Viper, Python, and others) are more complex than factory systems because they interface with the vehicle's immobilizer, security system, and various sensors through bypass modules. These additional connections create additional failure points.
The most common aftermarket remote start failure modes: bypass module losing its programming (the bypass module is a secondary device that tricks the immobilizer into allowing keyless start -- if it loses its programming, the immobilizer blocks remote start), loose or corroded wiring connections (aftermarket systems involve significant wiring harness work), and firmware that is out of date with the vehicle's current software version.
For aftermarket remote start issues, the best first step is to contact the shop that installed the system. Reputable installers provide some form of service warranty on their work and can diagnose system failures. If the installing shop is no longer available, a qualified automotive electronics shop can diagnose and repair most major aftermarket remote start systems.
For remote start systems operated through a smartphone app (Compustar DroneMobile, Viper SmartStart, etc.), also check whether the app needs an update, whether the vehicle's cellular connection to the remote start module is active, and whether the account subscription is current -- some smartphone-based remote start systems require a paid subscription to maintain the cellular connection.
Factory Remote Start Faults
Factory remote start systems are generally more reliable than aftermarket systems because they are engineered as part of the vehicle's electrical architecture. When factory remote start fails, common causes include: active vehicle fault codes (any check engine, transmission, or body fault code can disable remote start on some platforms), brake fluid level sensor triggering a low-fluid condition, or a software update that changed remote start behavior.
For factory remote start failures, connect the vehicle to a code reader or have a shop pull fault codes. If active codes are present, address them first -- some vehicle platforms will restore remote start automatically once the underlying fault is cleared.
Some vehicles experience factory remote start deactivation after a battery replacement or power interruption, similar to the key recognition issue described in a separate article. In these cases, the remote start system may need to be re-initialized through a dealer diagnostic session or by a locksmith with manufacturer-specific programming access for the relevant platform.
Do This
Replace the fob battery first -- even if other fob functions work, remote start range requirements may be higher
Verify the correct activation sequence for your specific vehicle's remote start
Check the hood pin switch for misalignment, especially if remote start recently stopped working with no other changes
Pull any vehicle fault codes before pursuing more complex diagnosis
Contact the installing shop for aftermarket system issues -- they know the specific installation
Don't Do This
Do not attempt to diagnose aftermarket remote start wiring without proper automotive electronics knowledge -- incorrect diagnosis can create new problems
Do not assume remote start failure means the system needs full replacement -- most failures are minor component or programming issues
Frequently Asked Questions
Can cold or hot weather cause remote start failures?
Extreme heat can cause battery voltage to drop temporarily, affecting fob transmitter range. In very cold weather (below 10 degrees), fob batteries lose voltage. Both extremes can cause intermittent remote start range issues that resolve as temperature normalizes. If the problem is weather-dependent and not present in moderate temperatures, battery replacement often resolves it.
My remote start worked last week. What changed?
The most common recent-onset remote start failures are: newly triggered vehicle fault code, battery beginning to fail (voltage dropping), and hood pin switch corrosion (more common in humid coastal Georgia conditions). Start with the battery and fault code check.
Can you reprogram my aftermarket remote start?
Depending on the system and what needs reprogramming, yes. We can assess aftermarket systems and reprogram bypass modules on many common platforms. Call us with the brand and model of your remote start system for a specific assessment.