How to test an ignition switch

How To Test An Ignition Switch | Electrical Troubleshooting 101

Ignition switches, although reliable for most times, can cause a wide range of issues. However, it’s not uncommon for car owners to experience no ignition problem for the lifetime of their car. On the other hand, an ignition switch may still become faulty from time to time. Even worse, a bad ignition switch can also produce a variety of symptoms that can seem like they are caused by some other issues. This is something that can be confusing for both drivers and mechanics and may lead to unnecessary repairs and expenses. To avoid situations like this, being able to identify bad ignition switch symptoms and what you should do to fix it might be greatly beneficial. To help you with this, here’s an article covering the most common symptoms, how to test an ignition switch properly and a quick look at the average replacement cost.

How to Tell if an Ignition Switch Might Be Faulty?

Despite having such a simple construction, the ignition switch performs several tasks in combination with other systems in your car. Because of this, concluding if the fault is within the ignition switch or some other component can be hard. There might be a situation where you turn the key, and nothing happens. The starter does nothing and dashboard lights don’t come on. The first thing that might come to mind is a dead battery or an electrical circuit fault. While this might very well be the source of the problem, the condition may also be caused by a broken key lock shaft.

Another common scenario is when you turn the key and the dashboard lights up, but there is no cranking sound. When trying to track down the problem, a faulty starter motor or a weak battery are some logical choices. However, worn contacts inside the ignition switch can also cause the same symptom. Sometimes, wiggling the key inside the lock may help overcome this issue, however, that is only a temporary fix.

Preliminary steps

In such a case, the first logical step is always to start by inspecting the most probable culprit. Moreover, the ignition switch is usually on the steering columns or dashboard. To access it and test it, you’ll most likely have to remove the steering column shroud or a couple of trims. To speed up the process, start by eliminating other components and parts that can cause various related issues.

Start by opening the hood and check the battery. Using a multimeter, make sure the battery voltage is over 12.6V. Anything below that might cause starting problems.

The next logical step is to inspect fuses and relays, which you will find inside a fuse box in the engine bay. Make sure that the starter relay clicks and provides power to the starter and that all of the main power distribution fuses are fine. In the end, you can also check if the starter motor is working by connecting the starter solenoid directly to the battery using a  jumper wire.

If everything seems fine, only then can you start suspecting that there might be a problem with the ignition switch.

How to Test An Ignition Switch the Right Way

If each of the previous tests left you empty-handed, you can turn your attention to the key lock and ignition switch assembly. Check the key itself before removing anything, as it could be worn out or damaged. If you have a spare key, use it instead of your regular one to see if there is any difference. Remember that newer cars have an anti-theft function, which will prevent the ignition if it doesn’t pick up the signal from the key fob or chip. To take this option off the table, scan your car’s PCM for DCT code with an OBD2 scan tool. If the immobilizer feature is defective, there should be a DCT code recorded in the PCM.

Inspecting the ignition lock shaft

Assuming that the key is in good condition, the only remaining suspect is the ignition switch itself. To check its condition and operation, you will need to gain access to it by removing surrounding plastic covers. The ignition lock is usually easier to remove than the ignition switch itself, which may be bolted using shear screws.

Removing an ignition lock

Depending on your car model, the procedure required to take out the ignition lock may differ. However, many of them work basically the same. Insert the key in the ignition, turn it to a certain position, push on the retaining tab, and pull out the key. The ignition lock should come out with it.

Inspect the ignition lock shaft and make sure it’s not bent, broken, and that it follows the lock when the key is turned.

Inspecting the ignition switch

Since most ignition switches are made of plastic, the ignition lock shaft might damage the plastic housing which may prevent the switch from turning. Once the ignition lock is out, you can easily see the slot in which the shaft sits. Just make sure it’s not damaged and that the edges are straight. Worn edges may cause the shaft to slip and turn independently from the switch.

Testing the ignition switch electrical circuit

Once you’ve ruled out other probable causes mentioned above, it’s time to test the ignition switch itself. There are many different techniques to verify the proper working of electrical components but here’s how to test an ignition switch the right way.

Reach for the ignition switch’s connector and unplug it. To perform the next step, you’ll need the help of your car’s repair manual. All cars are different so it’s impossible to troubleshoot an ignition switch problem without knowing which pin does what.

Wiring diagrams

Find the section covering power distribution and the ignition switch diagrams. Of course, you’ll also need to have some basic knowledge about how to read car wiring diagrams. Wiring diagrams found in repair manuals are essential to find and locate faulty electrical components, however, they can sometimes be quite complicated to understand for newbies. Make sure you correctly understand the signs and symbols used so you don’t end up with a wrong diagnostic.

Here’s an example of a starting system wiring diagram and how you can use it to find out whether the problem is related to the ignition switch or the car’s electrical system instead:

Ignition switch wiring diagram

Analysis

The first thing to do is to thoroughly inspect the wiring diagram so you actually understand everything that is at play here. Locate the components and make sure you understand where the power is coming from, where the unit gets its ground from as well as the various fuses, relays, and modules used to manage the system.

Based on the diagram above, here’s a couple of deductions you should be able to come up with:

  • The ignition switch gets its power from Fuse #23. The light blue/red wire coming in the switch connector should output the battery voltage.
  • The ignition switch is controlled by various modules and sends signals to the sentry key remote module, the BCM, and the park assist module, just to name a few.
  • When the clutch pedal switch is closed (on manual transmission models), the ignition switch sends back the signal to make the starter motor relay click. If the clutch switch is faulty, the starter won’t spin no matter how hard you turn the ignition key.

Following your car’s specific wiring diagram, identify where the power and ground are coming from and write down the corresponding wire colors.

Once it’s done, you can start testing the wires at the ignition switch connector to make sure everything is fine from the electrical system’s side. Take out your multimeter and see if power is coming from the battery wire. Do the same thing with the ground wire. If for some reason, there’s no power or ground, an open circuit and somewhere or a faulty module might be the problem. In that case, the ignition switch is probably fine and you’ll need to perform more extensive electrical troubleshooting.

Testing the ignition switch

If everything is fine with the circuit and the switch is correctly supplied with power and ground indeed, there must be something wrong with it. However, it’s still important to test the switch and confirm that it’s actually faulty. Doing so will make sure you didn’t make any mistakes in the troubleshooting process or missed a hidden unit or faulty sensor somewhere. Also, always keep in mind that wiring diagrams often include only certain components of a system and frequently leave some modules out to include them in a different diagram. For example, it’s fairly common for the power and ground circuits for the same unit to be on different diagrams, the former being in the “power distribution” diagram while the latter is in the “ground distribution” diagram instead.

If you can’t access the plug side of the switch properly, you can always take it out from the steering column so you can test it on your workbench. Most ignition switches are simply held in place with plastic tabs. Just lift the tabs and carefully pry the switch out using a flathead screwdriver.

How to test an ignition switch

Continuity test

Once it’s done, find the continuity diagram for your vehicle’s ignition switch. This diagram shows how the internal circuit works and which pins should have continuity and which shouldn’t. In the case where the ignition switch’s internal circuit would be open or short-to-ground, you’ll notice that some of the pins may not have continuity where they should or vice-versa.

Here’s an example of an ignition switch continuity diagram and the corresponding pins inside the connector:

Ignition switch continuity diagram

As you can see on the diagram, when the ignition lock is at the “0” position, there shouldn’t be continuity between any of the pins. Once it’s turned to the “I” (ACC) position, there should only be continuity between the WHT/RED and WHT wires. When it’s turned to “II” (ON), the WHT/RED wire should be connected to the WHT, BLK/YEL, and BLK/RED wires and so on.

Any anomaly found in the continuity will let you know that the ignition switch internal circuit is faulty. At this point, there’s not much else to do but to replace it.

Word of warning

To test a circuit’s continuity, the multimeter sends a 1v positive signal out from one of the probes and then monitors the power input coming from the other one. This is also how it tests the resistance of a given circuit. Now, since most electronic components work at a much lower level than 1v, it’s important to always unplug every connector related to a component before testing it. Never use the back-probing technique to save time. Doing so risks sending a higher voltage into the circuit than what they can endure and may fry expensive electronic components. The same thing applies when testing a specific wire. Always unplug both sides of the wire beforehand. Trust me, you really don’t want to send a 1v input into your car’s powertrain control module.

Ignition Switch Replacement Cost

When the ignition switch on your car goes bad or starts showing signs of possible upcoming failure, it will need to be replaced. Recent switches are encased in a sealed plastic housing and can only rarely be opened. And even if it was possible, most ignition switches are quite inexpensive anyway.  Trying to fix it makes little sense. Another thing to consider is that you already have to remove various interior parts to get to the ignition switch and test it. At this point, replacing is the only logical option.

Depending on the car model you drive, the ignition switch may or may not come with the key lock integrated into one assembly. As a general rule, it’s safe to say that an individual switch is less expensive than lock assemblies. Moreover, just like any other car part, more expensive vehicles usually come with a bigger repair price tag. The ignition switch on a Ferrari is obviously more expensive than one for a Toyota Yaris.

Average cost

To give you an idea of how much the switch might be on your car, here’s a quick overlook of the average replacement cost for an ignition switch based on different models:

  • 2016 Hyundai Accent: $16.62
  • 2013 Honda Civic: $31.79
  • 2015 Mitsubishi Lancer: $47.79
  • 2018 Infiniti Q50: $82.79
  • 2017 Alfa Romeo 4C: $101.79
  • 2018 Porsche 718 Cayman: $120.79

Labor cost

The ignition switch replacement cost really depends on where you plan to have the work done. Generally speaking, the dealers’ labor rate is somewhat higher than independent repair shops. And independent shops are more expensive than fixing the problem by yourself.

Luckily, replacing an ignition switch is not that hard. The most complicated part is always the troubleshooting process. Once you’ve found what’s wrong, you’re already more than halfway done.

In most cases, replacing an ignition switch shouldn’t take more than 2 hours. With a labor rate at around 100$/hour, the dealership price tag should be around $200 plus the cost of the part itself. If you decide to opt for the independent repair shop option instead, you could save 50-$60 or more.   Obviously, if you decide to replace it yourself, you’d save all of it.

Depending on the kind of car you drive, however, the price mentioned above might differ. Cars with the ignition switch installed on the dashboard or center console might require a little more time. Gaining access to the switch itself is quite easy when the key lock is on the steering column. In cases like that, you only need to remove or drill a few screws and bolts and remove the surrounding plastic coverings. However, things can get a bit more complicated when the car has a dash-mounted key lock. With a setup like this, you first must remove various interior parts before reaching the switch itself and removing it.

Last Words

As explained in this article, a bad ignition switch can cause various issues, each related to different symptoms. Luckily, troubleshooting and learning how to test an ignition switch is not that hard at all. All you need is to learn the basics of reading electrical diagrams,  follow the manufacturer-recommended procedure found in your car’s repair manual and a bit of practice. That being said, always keep in mind that, when in doubt, your best bet is still to ask a trustworthy auto mechanic for advice.

When it comes to the ignition system, you’re always better safe than sorry.

About Bojan P

Avatar
My name is Bojan - I am a car enthusiast, specialised in the vehicle diagnosis, repair and maintenance with 10 years of practical, hands-on experience. In addition, I have a Masters degree in mechanical engineering.

Leave a Reply

Your email address will not be published. Required fields are marked *