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Common Symptoms of a Faulty Ignition Switch

By R&D
Published on September 1st, 2025

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The ignition switch is a vital component of a vehicle's electrical and starting system. It is typically located on the steering column behind the ignition lock cylinder. Working in tandem with the lock cylinder, the ignition switch allows the driver to power on the vehicle’s various systems and start the engine. It operates mechanically by changing the position of its internal contacts when the key or ignition is turned, directing power to specific circuits while cutting power to others.Modern ignition switches generally have four distinct positions, each serving a specific purpose:

Common Symptoms of a Faulty Ignition Switch

Off/Lock: Disconnects power from most circuits, but non-ignition circuits such as interior or exterior lights remain operational.
Accessory: Powers non-essential systems such as the infotainment system, power windows, and dashboard lights without starting the engine.
Run/On: Powers the vehicle's primary systems, including Heating, Ventilation, and Air Conditioning (HVAC) controls, dashboard instruments, and engine controls.
Start: Powers the starter circuit and activates the starter motor to crank the engine. This position is only engaged momentarily during the engine-starting process and automatically returns to the Run/On position once the engine runs.

A faulty ignition switch can lead to various issues, such as the inability to start the engine, intermittent electrical failures, or complete loss of power to critical systems. These malfunctions can compromise vehicle performance and safety, making timely diagnosis and repair essential.

This article highlights the typical symptoms of a faulty ignition switch, to help you identify potential issues and their root causes.

What Causes Ignition Switch Failures?

Corrosion on the Terminals: Over time, exposure to moisture or environmental contaminants can lead to corrosion on the ignition switch terminals. Corroded terminals hinder the flow of electrical current, causing intermittent or complete failure in the ignition system.
Worn Ignition Switch Contacts: Frequent use of the ignition switch leads to wear and tear on its internal contacts. As these contacts degrade, they may no longer maintain a reliable connection, resulting in issues such as difficulty starting the engine or erratic electrical behavior.
Faulty or Loose Wiring Connections: Wiring issues, such as frayed or damaged wires, combined with loose or improperly connected terminals, can disrupt the electrical flow to the ignition switch. These problems often result in intermittent connectivity, leading to complete ignition failure.
Electrical Surges or Shorts: Sudden electrical surges or short circuits in the vehicle's electrical system can damage the ignition switch’s internal components. These conditions may completely burn or warp the switch contacts, rendering them inoperable.

Common Symptoms of a Faulty Ignition Switch

1. Vehicle Shuts Off While Driving

A sudden shutdown while the engine is running is a common indicator of a failing ignition switch. If the switch loses functionality mid-operation, it can cut power to critical systems such as ignition and fuel delivery, leading to engine shutdown. In some cases, the vehicle may or may not restart after a brief period, depending on the severity of the failure.

2. Engine Fails to Start

Another sign of a defective ignition switch is an engine that won’t start. The ignition switch is responsible for controlling the application of power to the starter motor, and engine controls. When these components fail to receive the necessary electrical power, the engine cannot turn over, often leaving the vehicle inoperable.

3. Engine Starts Then Shuts Off

A faulty ignition switch may cause the engine to start but immediately shut off. During cranking, the ignition switch provides momentary power to the fuel pump and ignition system, allowing the engine to start. However, if the switch fails in the “ON” position, power is cut off as soon as the key is released, resulting in an immediate engine shutdown.

4. Accessory Power Issues

Difficulty powering vehicle accessories, such as interior lights, dashboard lights, or infotainment systems, can also point to ignition switch issues. When the key is turned to the “ACC” position, the ignition switch should supply power to these systems. Failure to do so may indicate a problem with the switch or the lock cylinder. It is essential to rule out related issues such as loose internal components or wiring problems for accurate diagnosis.

5. Difficulty Turning or Removing the Key

Trouble turning the key in the ignition or removing it can signal a worn-out or failing ignition switch. This symptom arises when the key fails to engage correctly with the switch’s internal mechanism. In some cases, the engine may continue running even after the key is removed, highlighting severe internal wear or electrical failure.

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The Innova Scan Tool quickly retrieves and identifies existing Diagnostic Trouble Codes (DTCs) stored in your vehicle’s computers. With a quick On-Board Diagnostic II (OBD2) Scan, you can retrieve existing DTCs, the I/M Status of the vehicle, and any collected Freeze Frame data from these computers. Refer to the Innova Coverage Checker to determine the level of information supported on your vehicle by year, make and model. The Innova Scan tool effectively diagnoses ignition switch-related issues, helping you easily pinpoint and resolve problems.