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.
What is ASD Relay?
An ASD (Automatic Shutdown relay) is a safety feature that prevents your car from starting without first turning on the ignition switch.
It’s meant to keep your vehicle safe while you are out and about; however, sometimes it can be an inconvenience when trying to jumpstart your battery or use jumper cables on another vehicle.
The starter motor won’t crank unless there’s enough current coming through the ASD relay in order for it to activate itself via voltage drop across its contacts (which means that if this happens, then we have no way of getting around by using just our own car).
The reason why this happens is that these relays require some amount of time before they will open up their contacts again after being turned off – meaning even though we might have enough power going through them initially if we don’t wait long enough before trying again then these relays might not activate fast enough on their own accord.
Construction of an ASD Relay
The ASD relay is a simple electromagnetic switch activated when 12 volts are applied to the coil. The relay has two circuits; one side controls the power to the fuel pump, ignition coil, and engine control module (ECM).
The other side of the relay contains a normally closed contact that allows current to flow through even when the relay is turned off.
This side of the relay is connected to the power control module (PCM) or ignition switch. The ASD relay also contains a diode that protects the coil from voltage spikes.
In a normal ASD, there are five terminals. The number and function of each terminal are as per following:
- Terminal 30: This terminal is connected to the battery and receives power through it.
- Terminal 85: It is the grounded terminal by the power control module.
- Terminal 86: This terminal is connected to the input power source, an ignition coil, or ignition switch in this particular case.
- Terminal 87: It is used to form a closed circuit that provides output supply to the components like fuel pump relay and fuel injectors.
- Terminal 87A: It is close to terminal 87 and performs a de-energizing function. When you turn off the engine, the PCM or ignition switch sends a signal to the ASD relay, which de-energizes the coil and opens the circuit by connecting this terminal.
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.
Bypassing the ASD Relay, What does it Mean?
If you are facing the engine start problem in the car, you should know how to bypass ASD relay to start the car engine freshly. You have to understand technical mathematics and check every point to understand the car parts’ present situation.
Its engine, fuel parts, and then proceed in every car, power supply done by fuel injectors, fuel pump, and ignition coil and these entire power tools controlled by a logic module, which is called ASD.
The main idea behind this is that while the key is off, immediate fuel pressure needs to shut off.
Additionally, during turned the key off, it helps to prevent your car from disabling or fire problems. Now the question is, how do you taste Relay in the car? Well, the answer is very simple.
Why Do You Need an ASD Relay?
In the past, cars didn’t have this feature, and it was up to the driver to make sure that everything was turned off. It carries several benefits to having an ASD relay in your car:
#1. New Car Have an Elaborate Electrical System.
ASD is especially important in modern cars because they have so many more electrical components than older models.
If even one of these components is left on when the engine is shut off or in the case of a short circuit, it can drain the battery or cause other problems.
ASD ensures that everything is properly shut down so that you can be confident that your car will start up again when you need it to.
#2. A Safety Feature for Engine Management System.
You could say that this is a safety feature that protects the entire engine management system. Electronic engine management systems are computer-controlled system that manages the engine’s ignition, fuel injection, and emission control systems.
The electronic engine management system constantly monitors the engine’s performance and makes adjustments to ensure optimum performance and fuel efficiency. It also helps reduce emissions by controlling the fuel injected into the engine.
The electronic engine management system is made up of several components, including the engine control module (ECM), throttle position sensor (TPS), mass air flow sensor (MAF), oxygen sensor (O2), and knock sensor (KS).
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:
#1. 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.
#2. 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.
#3. 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.
#4. 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.
How to Detect Causes Behind ASD Relay Malfunction?
To detect the causes behind ASD relay malfunction, you will need to check some components of your car and engine, such as high temperatures, a damaged motor, and a dirty connection on the ASD relay board are some of the things that cause the Asd to malfunction.
Other causes include:
- Insufficient control of the car’s fuel system.
- Too high electrical currents flow through the relay.
- Chemicals, salt water, and other liquids may have entered into essential components, such as the transistor, connector, and circuit board.
How to Know When You Need To Bypass ASD Relay?
To know when to bypass ASD relay is if your car doesn’t start. Another reason is when you’re pressed with time and need a quick jump start. You might also need to bypass the relay when using jumper start cables on another car.
The car won’t start
The automatic shutdown relay can prevent your car from starting for several reasons. Some of them include a dead battery or a problematic starter motor. If your car can’t start using the usual way, bypassing the Asd relay could be the only option.
To save time
You may also bypass the ASD relay if you want to save time. For instance, your battery could be dead, but you still want a quick jump start without waiting for the ASD to activate.
Besides, ASD sometimes requires time before reopening its contacts after being turned off. That means there may be enough power flowing through the relay, but it will activate slower than you want.
When using jumper cables on another car
If you want to jumpstart another vehicle whose ignition switch is turned on (or doesn’t have one), you must bypass the ASD relay. That’s the only way you’ll get the car to start.
How to Bypass ASD Relay (Step-By-Step Guide)?
#1. Power module ASD relay.
Step 1: Using a wrench, remove the negative battery cable. When you set it aside, make sure it doesn’t touch any metal.
Step 2: Find the ASD relay (your owner’s manual will have this information). If you don’t have your car’s manual, contact a dealership.
You will need to know if it is a single relay or situated in the power module (located in the relay box or the firewall).
Step 3: Locate the wiring harness connector on the power module and unplug the harness (usually found near the front passenger side). If your car has a screw that holds the plugs and the tangs, unscrew and remove this.
If not, use your fingers to move the tangs on the plugs. Then, pulling the tangs apart, remove the connector from the power module.
Step 4: Loosen and remove the bracket securing the power module using a socket wrench. Placing the new power module in its place and reblot it, and plug the harness wiring back in.
Note: If it needs screwing down, do so without over-tightening the screws, this can damage the connector’s pins, and the housing, which is plastic and will crack if the bolt is too tight).
To make sure the power module and ASD relay are working correctly, start the car, then reattach to the battery the negative battery cable.
#2. Power module with separate ASD relay.
Step 1: Using your owner’s manual, find the diagram of your relays and fuses and locate the faulty relay.
Step 2: Remove the faulty relay with your fingers or a pair of pliers. Use a rocking motion from side to side as you pull upwards.
Step 3: Replace the faulty relay with the new relay by pushing it into place without damaging or bending the connection or the terminal.
The new relay should slip easily into the space. Then start the car to make sure everything is working.
#3. How to relay bypass one wire.
Step 1: PCM relay removal
You can remove the PCM relay using your fingers. It should pull out easily.
Step 2: Does the car start?
Once it is out, the car will no longer start.
Step 3: Position the cable in the 12V output terminal
Take your double-ended cable and place one end in the 12V output terminal and the other end of the plug in the PCM. This wire will be the relay while the ASD relay is out.
Step 4: Power the PCM with the cable
While the one end is in the 12V output terminal, place the other end in the PCM.
Step 5: Listen for the fuel pump prime
As you push the wire’s end into the 12V output terminal, you will hear the fuel pump priming followed by a few soft clicks. Get in the car and start the engine.
Step 6: Pull off the cable to shut off the engine
Get out of the car and remove the bypass wire. The vehicle should go off immediately.
#4. Quick ASD relay bypass tips.
- While removing cables or wires, be sure to keep them away from metal. You don’t want to short out anything or get zapped with electricity.
- If using pliers to remove the relay, be careful not to damage the plastic housing on the automatic shutdown relay.
- When tightening the power module bolts, do not over-tighten the screws because it will damage the power module connector’s pins.
How to Test a Bad ASD Relay?
In this section of the article, we’ll show you how to test a bad ASD relay in your car.
Tools Required
- A test light or multimeter
- Jumper Wires
Procedure
#1. Park Your Car.
Park your car on level ground and set the parking brake. Turn off all accessories and the engine. Open the hood and prop it up.
#2. Locate the ASD Relay.
Locate the ASD relay. It is usually mounted on the fender well or inner fender near the battery. The relay will have four terminals labeled 30, 87, 87a, and 89. It looks just like your normal fuel pump relay.
#3. Remove the ASD Relay.
Remove the ASD carefully from its socket. Some relays have a locking tab that must be depressed before removing the relay.
#4. Testing the Terminals.
Terminals 30 and 87A
Set multimeter to the continuity setting. Check for continuity between terminal 30 and terminal 87A. There should be continuity. If there is no continuity, the relay is bad and needs to be replaced.
Terminals 85 and 86
Now, set your multimeter to the ohms setting X1. Connect the multimeter between 85 and 86. The relay is good if the multimeter reads between 70 and 80 ohms. If it reads infinity or OL, the relay is bad and needs to be replaced.
Terminals 30 and 87
Now, it is time to test terminals 87 and 30. One of these is the de-energized terminal, so if you connect these two terminals and there is continuity, the relay is bad. If there is no continuity, the connection is good.
#5. Final Continuity Test.
This one is probably the most important test. This is the test that will show if the relay is actually working or not.
- Connect terminal 85 to the negative side of the 12-volt power supply with the help of a jumper wire.
- Connect terminal 86 to the positive side of the 12-volt power supply using another jumper wire.
- This should activate the relay.
- Now, using your multimeter in the continuity setting, check for continuity between terminals 30 and 87.
- There should be continuity. If there is no continuity, the relay is bad and needs to be replaced.
As you can see, testing a bad ASD relay is not that difficult. All you need is a test light or multimeter and some jumper wires. With these tests, you can easily determine if the relay is bad or not.
Advantages and Disadvantages of The Bypass ASD Relay
If you can use the technique properly, there shouldn’t be any trouble after bypassing the ASD. But every process has some pros and cons.
Advantages
- You can drive the car with no major issues
- Keeps the engine functioning
- Gets you enough time until you find the real problem
Disadvantages
- Can cause damage to the electrical system in future
- Any wrong move can damage the circuits
How Much Does an ASD Relay Replacement Cost?
Automatic shutdown relay replacement costs vary depending on the model of your vehicle and location.
For most cars, you can expect to pay $80 to $110 for a new ASD relay. However, you will need to dig your pocket deeper for some cars, especially luxury vehicles.
For example, an ASD relay Jeep replacement can cost you between $120 to $200 or more. For a BMW, the automatic shutdown relay can cost up to $300! A dodge ram 1500 auto shutdown relay costs between $105 to $115.
This price is inclusive of parts and labor. The cost of replacing the dodge auto shutdown relay may also vary, depending on the model year.
FAQs.
Q: 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.
Q: 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.
Q: 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.
Q: 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.
Conclusion
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.