How To Find A Short In A Car

When we talk about car wiring, one of the most common problems drivers often encounter is electrical short. It can be hard to locate where the short originates; however, there are some guidelines that you can follow to find and fix the issue more quickly. To begin with, you should check to see if there is any loose or damaged wiring in your car’s electrical system.

In this article, I will recommend for you the way to find a short in a car.

Definition Of A short

Generally speaking, a short, also called a short circuit, is an electrical fault in a car’s wiring system. To be more specific, this issue happens when the wiring harness deflects or changes the flow of an electrical current to an unintended path instead of the route it’s supposed to pass by. A short circuit can cause many problems to your car.

The Working Principles Of A Circuit In The Electrical System Of A Car

To clearly understand the nature of a short, first and foremost, you need to know how electricity circulates through your vehicle.

There are two main kinds of circuits in your car: sensor circuits and actuator circuits. While sensor circuits handle such sensors as wheel speed sensors, light sensors, or coolant temperature sensors, actuator circuits control the mechanics, in other words, the opening and closing of different parts.

For example, one sensor circuit runs between the engine control module (ECM) and the engine coolant temperature sensor (ECT). You can find these two sensors behind the glove box and engine in many cars.

When the wiring is in good condition, electricity can flow freely between these ECM and ECT sensors. In the example mentioned above, the ECM sends a 5V reference voltage to the ECT, causing it to change its resistance according to the temperature.

The working principles of a circuit may sound complicated. Still, it is vital to remember that your vehicle’s electrical system can only function properly if the wiring harness is in a good state and uninterrupted. When an excessive current appears in a circuit, electricity can’t flow properly, leading to some components’ malfunction.

Different Types Of Short Circuits

There are two main types of short circuits: short-to-ground and short-to-power.

Short-to-ground happens when an electrical current is transferred from the circuit to the car’s frame, resulting in blown fuses, damaged components, etc.

On the other hand, short-to-power often occurs inside the wire harness. When cut or open wires contact each other, the current will flow to where it is not supposed to. This condition can cause the headlight switch to activate the horn unintendedly, for example.

Understanding the difference between these two short circuits is necessary because it can help you determine what type of short circuit you’re encountering, therefore, saving time locating the fault.

Procedure To Locate A Short Circuit In Your Car

Looking for a short in your car can be difficult and time-consuming, even when you have enough experience and necessary tools in your hand.

First, prepare an EWD (electrical wiring diagram), a multimeter, and some tools for opening the car’s wire harness and instrument panels.

Open Your Car’s Circuits.

The first step in troubleshooting the circuit is opening the car’s wire harness and viewing your EWD. You have to understand the different wires and electrical diagrams in the EWD to know what to do next. The wire colours in the system should match the colours illustrated in the EWD.

Check Each Fuse Individually.

Each different wiring system in your car should have a corresponding set of fuses.

To check fuses to see if there are any easy-to-reach short circuits, you can do as follows:

Randomly remove a fuse and connect your multimeter to the terminals for the fuse. The multimeter will indicate electrical continuity if an electrical current is detected. You may use a light tester instead of a multimeter. In that case, the light tester will light up if an electrical current is present.

If the multimeter fails to indicate any continuity or the test light does not light up, the current is not flowing to that fuse, so you can guess that the faulty wire can be somewhere in that path. Find the location of the wire in the EWD and check it thoroughly.

Repeat this procedure for each fuse to help track down the problematic area.

Check For Issues Along A Wire.

If you suspect any abnormalities in a specific wire, disconnect the wire’s connection to either the sensor or load endpoints. Use your test light or multimeter to track down where the fault occurred. Find out whether electricity flow stops at the sensor or load.

Inspect Any Visible Abnormality In The Wiring.

You might also save time and effort by inspecting any visible wiring problem at first. If lucky, maybe you can find a chafed wire which you can immediately repair to fix the issue. However, most cars’ wire harness is carefully covered, so in most cases, you have to open up some panels to find where the problem is.

5V Circuit Testing.

If you think that the short circuit is a 5-volt circuit, which are circuits that ECM uses to control the transmission and engine, you can disconnect your battery and the ECM one after the other. Measure continuity using the multimeter and probe between the circuit and the car frame. By doing this, you can detect electrical fluctuations and find out where the short is.

Work After Finding A Short Circuit

After finding a short, it is time for you to continue to repair the faulty electrical wiring. It can be a minor fault that requires you to fix only the wire’s casing. Otherwise, you may need to replace the whole wire to fix the problem once and for all.


It is essential to know the method to quickly find a short circuit because it can help you to save time and effort and make sure that you are driving a safe and well-functioned car. Although the above-mention guide can be long and tedious, it may prove helpful to you in case of an unexpected problem.

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