How to Bypass ASD Relay – All That You Need To Know

The ASD relay is an acronym for Automatic Shutdown Relay, but its acronym is popularly known. It is a major component of the fuel and ignition systems of modern vehicle engines. “This component performs the task of transmitting power (switched 12-volt) to the ignition coils and fuel injectors of vehicle engines,” which gives room to produce a spark and also allows the pumping of fuel.

With this article, you will be educated on how the ASD relay functions, what is required to bypass the ASD relay, the step-by-step process on how to bypass the ASD relay, and finally, the pros and cons of bypassing the ASD relay.

The ASD relay, through the logic module, controls some parts of the power module; it is designed in this manner in order to avoid problems like dieseling or fire outbreaks by immediately stopping the ignition system and fuel pressure when the engine has stopped running.

how to bypass asd relay

How does ASD relay work?

  • First, terminal number 30 is connected to the battery voltage. Note that terminal 30 is always connected to the battery for both the fuel pump and the automatic shutdown relay.
  • The Powertrain control module grounds the ASD relay from the side of the coil through terminal 85.
  • Voltage is being supplied to the coil side of the ASD relay by terminal 86
  • The powertrain control module stops the function of the fuel pump and ASD relay. Terminal 30 is being connected to terminal 87A in an off position.
  • The rest of the circuit is not being supplied with power.
  • When the fuel pump and automatic shutdown relay are powered by the powertrain control module (PCM), terminal number 30 connects to terminal 87 in an on position. Voltage is being supplied to the remaining part of the circuit by terminal number 87.

When the vehicle’s engine is immediately up and running, the automatic shutdown relay kicks off, supplying a switched power of 12+ volts to the ignition coil and fuel injectors; this helps to allow the smooth operation of the engine system.

Therefore, when the vehicle’s engine is then turned off, the ASD relay shuts down all of its activities immediately as a preventive measure to safeguard other engine components and the whole vehicle. With the aid of some emission packages, the ASD relay provides 12+ volt power to the oxygen sensor heater relay and sensor heating elements of the vehicle.

The power control module controls the function of the circuit within the ASD relay, which means that when the power control module switches the circuit On or Off, it simultaneously starts or stops the automatic shutdown relay operation. The ASD’s main function is to provide 12+ volt power to the vehicle’s O2 sensor heater elements, fuel injectors, ignition coil, and car alternator field.

ASD Relay

When and why required to bypass ASD relay

In order to prevent engine knocking, most motorists see the need to bypass the ASD relay function of their vehicles. If you are struggling to start your engine, you need to know how to bypass the ASD relay so that you will be able to start your car, as this could be the fault. Below are some of the ASD relay symptoms that indicate a faulty relay:

Stalling the engine when it starts

It is one of the first commonly noticed symptoms that reflects a faulty automatic shutdown relay in an engine. At intervals, you will experience a delay in the operation of the engine when you turn it on. Interference with the supply of power to the injectors or ignition coil by the ASD relay can give rise to ignition coil problems and other problems with the various engine components.

The check engine light will be illuminated.

When there is an issue with the automatic shutdown relay, the computer system of the vehicle illuminates the check engine light, signaling the driver that there is a problem with the driving vehicle. Though this symptom is not a certain way of confirming that the ASD relay is bad, a vehicle scan is still required to be sure of the actual cause of the illuminated engine light.

The engine fails to convert power into motion.

If the engine fails to convert power into motion by turning the crankshaft, it signifies a bad ASD relay. Due to the fact that most parts of the engine system are wired together if a circuit becomes faulty due to a faulty relay, it might damage other circuits. An automatic shutdown relay that is bad can make a starting circuit not function, preventing the engine from kicking off when the ignition key is turned.

A detailed process on how to bypass ASD relay

For you to be able to bypass the ASD relay successfully, you must understand the ASD relay wiring diagram and the techniques needed to carry out this task. There are various kinds of mechanic tools needed for this task. Some of the tools include a 12V DC 120 Amp 4 pin, plier, four pins 40/30 AMP 12 VDC harness, screwdriver, etc. It is better for you to use tools manufactured by a standard company to avoid any form of issue while using them.

Also, check the tool manual so that you can have the knowledge on how to properly handle the various tools you are going to use.

Below is a three-step process on how to bypass an ASD relay successfully:

how to bypass asd relay dodge ram

How to Bypass ASD Relay (Step-By-Step Guide)

Step 1: The foremost and most appropriate step to take is to open the power module of your vehicle that houses the ASD relay. Go to the section that is spring. If your vehicle’s coil is not powered up at that time, you then need to spring close the contact.

Step 2: Now you have to energize the coil of your vehicle so that you can have a flexible contact, which you are going to pull. This allows the flow of current, which helps to prepare the other contact. For you to be able to pass this step, you need to understand the ASD relay wiring diagram properly.

Step 3: Below the relay, locate the path that allows the flow of current, and from this position, even when the relay coil is not fully energized, there will be a flow of current. Now, you have to remove the fuel pump and replace it with an electric fan. There are two pins that control the automatic shutdown relay: #87 and #30. You will wear a jumper on those pins to enable you to bypass the automatic shutdown relay.

If you critically follow the ASD relay wiring diagram and the steps given above, you will be able to bypass the relay with ease and successfully. This relay is not a contraption; it is very easy to understand and manipulate. Once you have been able to bypass the relay, you have to test the ASD relay by checking its terminal resistance using an ohmmeter.

Pros and Cons of the Bypass ASD Relay

A lot of motorists ask questions like: is it safe to bypass the ASD relay? Is it dangerous to do this? What are the long-term effects? Will this damage my whole vehicle?

I am going to help you with some information that will help ease your worry. Bypassing the ASD relay in your vehicle is a safe move. Personally, I do not think that it will damage the vehicle only if it is done properly. It is because the power will still run through the stock wires that it was originally made to pass through.

It is true that the full power only runs in short bursts, so the system, by default, sets to 100% full power as a failsafe measure. The engine circuit was originally made to receive the full voltage of the stock pump. It has a well-sized fuse that protects it from getting damaged, so you have no worries.

But you have to know that if the wires are very old, for instance, about 15 years old, I cannot guarantee their efficiency due to the fact that they might be worn out. So, it is advisable to change the wiring system at this point.

The long-term effect of bypassing the ASD relay is quite uncertain as there are many factors to consider. There might likely be a reduction in the engine’s lifespan, but not to a very significant extent. But again, the lifespan of the engine can also decrease on its own due to other factors, and it might not necessarily be as a result of the bypass.

Do not worry about the effect of adding the voltage directly to the fuel pump. You should note that electric motors, to an extent, are more effective at a higher voltage. For instance, you want to upgrade your vehicle. Instead of bypassing the ASD relay, most mechanics recommend that you do a complete fuel pump rewire because bypassing offers little or no benefit at all over the original setup.

Also, properly rewiring your car increases the performance of the engine. It will always benefit you to replace old wiring systems.

Frequently Asked Questions (FAQs)

What is the ASD relay for?

The Automatic Shutdown (ASD) relay controls the power supplied to the fuel injectors, ignition coil, oxygen sensor heater elements, and other parts of the power module. The ASD relay shuts down the fuel ignition and the fuel pressure immediately after the ignition key is turned off; this is done to prevent problems like fire, dieseling, etc.

How is it possible to jump a fuel pump relay?

To jump a fuel pump relay, you must first locate the relay; it is located in the front seat under the passenger’s carpet. The relay terminals are always marked with numbers. With the aid of a jumper, jump across terminal number 30 to terminal number 87 while the ignition key is ON.

Please note that the key must be ON unless it will not work. You need to know that all Bosch relays are similar no matter how and when it is produced.
If your fuel pump relay is faulty, this is the only way for you to run your fuel pump and get your car started.

What are the symptoms of a bad ASD relay?

When the Automatic Shutdown Relay (ASD) has failed or is failing, the driver will notice certain indicators or few signs. The first symptom to notice is the stalling of the engine when it starts; there will be a delay in the operation of the engine when the ignition key is turned on.

Secondly, the engine will not crank; the engine will not be able to convert power to motion, which means that the vehicle will not be able to move. Lastly, the check engine light will be illuminated; the check engine light shows the driver that there is a problem, but it might not necessarily be the fault of the relay as the light is used to indicate several issues.

What is an ASD fuse?

The Automatic Shutdown (ASD) fuse is a vital electrical component in the electronic engine management systems, consisting of both the ignition and fuel systems. This component is very important in maintaining the functionality of a vehicle.

Is it safe to bypass the ASD relay?

If you have a problem starting your engine, it is safe to consider bypassing the ASD relay of your vehicle, but first, you have to understand the techniques and tools needed for performing this task. For example, knowing the ASD relay wiring diagrams so that you can avoid damaging other engine components. If you cannot fully understand how to bypass the ASD relay. The most reasonable option for you is to hire a mechanic’s services to assist you in carrying out this task.


The function and purpose of the automatic shutdown (ASD) relay cannot be easily overlooked. Of course, this relay is subject to wear and tear, like most electrical components.

Therefore, if damaged, immediate attention should be given so that it will not affect the vehicle’s entire engine system’s performance. If you find out that the relay is faulty, please make sure you know how to bypass the ASD relay before attempting it on your vehicles. Regularly check if the automatic shutdown relay has started to rust and check for bad wires under the ASD relay box.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

Leave a Reply

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

Recent Posts