Reset EFI Relay

[geocook717]

With regards to resetting the EFI relay, is it really as simple as pulling the relay for 30 minutes and then plugging it back in? Is there any negatives to doing this? Or anything I can screw up in the process of resetting this relay?

 

[octanejunkie]

With regards to resetting the EFI relay, is it really as simple as pulling the relay for 30 minutes and then plugging it back in? Is there any negatives to doing this? Or anything I can screw up in the process of resetting this relay?

What are you looking to accomplish?

 

[geocook717]

Well, I was reading through the "new owners" guide here on the forum. Pulling the EFI relay was one of those items referenced. I believe the goal is to get better mpg. I guess I was curious if this was something I should do with the new to me runner. In pulling and reseating the relay, the post indicates that the vehicle will then adjust to my driving more quickly.

 

[SpidermanGeek]

It's not a process that will give you better MPGs per say, but it does reset the EFI to factory and kickstarts the "learning process" of the mapping right away.

If you've done any maintenance that is fuel delivery, intake air delivery or ignition spark related, the vehicle's computer can start optimizing the relationship between all of these components that much quicker.

If the previous owner was a lead foot and you're a more conservative driver, then yes, there can be a benefit to the vehicle "tuning" itself to your driving style that much quicker.

But pulling the EFI relay is just one of those things that "should" be done after some maintenance to the engine (like new spark plugs or a MAF cleaning), but really isn't a necessaity.

Bottom line, it never hurts to pull the EFI relay for a reset, but you shouldn't expect it to actually solve anything.

If you're just pulling it for the sake of the vehicle learning your style of driving, chances are that the difference in MPG will be negligible, but likely still a step in the right direction.

You won't "hurt" anything by doing this (unless you totally screw up one of the simplests of mechanical tasks such as this one, ie: try to jam the thing back in, in the wrong hole).

 

[alanflies]

I'm sure it's just semantics but I hope you guys are talking about the EFI fuse. The fuse that powers the ecu, not the EFI relay. Pulling and re installing the EFI relay will do nothing.

 

[SpidermanGeek]

According to the 3rd Gen Buyer's Guide, 4-ripcord refers to it as the relay.

Reset EFI relay:
When you buy a used vehicle, you want to reset the EFI relay. Its a trade secret among used auto dealers. The reason for this is the EFI map that the vehicle has set to work with its past driver. When you reset this map, the vehicle forgets how the old driver used to drive and learns how you drive. It picks up on how you accelerate, how you cruise, etc and maps the fuel injection to follow. It takes about 1 tank of gas for it to establish a new EFI map. Doing this will not always net an MPG gain, but it will make the vehicle feel more peppy. Even if you don't reset the EFI relay, the vehicle is always adjusting it's EFI map and will eventually get used to you, but resetting it is a lot more effective.

It is also smart to do this whenever you significantly change anything in the drivetrain, such as a new filter, cleaning intake components, add cold air intake, bigger tires, exhaust system, etc..

To do this, find the largest of the EFI relays in the fuse block on the drivers side of the engine bay. With the battery still connected, remove this relay for 30 minutes then re-install. Done.

Pulling either the fuse or the relay doesn't really matter though, both of them will cut the power to the ECU.

 

[alanflies]

According to the 3rd Gen Buyer's Guide, 4-ripcord refers to it as the relay.



Pulling either the fuse or the relay doesn't really matter though, both of them will cut the power to the ECU.

Take a look at the wiring diagram. You must pull the EFI fuse to reset the memory in the ECU...

When you turn the key, the ECU (MREL) outputs 12vdc through the relay to ground. This triggers the Relay to close and send power back to the ECU and other components through a higher amperage circuit. Removing the relay is the same as turning the key to off...The only way to remove constant 12vdc from the ECU is to remove the EFI Fuse.

 

[TheDurk]

Take a look at the wiring diagram. You must pull the EFI fuse to reset the memory in the ECU...

Yep. Whoever wrote that article is an idiot. It wouldn't make sense for the volatile memory to be connected to the EFI relay because it would be erased every time the relay cycled. You have to pull the fuse.

And just to put a nail in it, the EFI relay cycles every time the key is turned off:

Per the factory EWD:

(7) Battery signal system
Voltage is constantly applied to TERMINAL BATT of the engine control module. When the ignition SW is turned to on,
voltage for engine control module operation is applied via the EFI relay to TERMINAL +B of the engine control module.

The BATT terminal gets power from the EFI fuse bypassing the relay. Sheesh.

 

[SpidermanGeek]

Yep. Whoever wrote that article is an idiot. It wouldn't make sense for the volatile memory to be connected to the EFI relay because it would be erased every time the relay cycled. You have to pull the fuse.

Although, in an older post relating to the EFI fuse/relay, you can be quoted as having said the following:

As far as I know, on our trucks, you can just pull the EFI fuse. No need to pull the relay. Either will do, but the fuse is easier. The point is to cut power to the ECU and force it to re-learn its settings.

That's why I thought that pulling either would do the trick.

Shouldn't somebody amend the buyer's guide?

Because I always thought you had to pull the relay for 30 minutes. And I've done so on a few occasions after some maintenance. And that's not the only spot on T4R that the relay is referenced. I would hate to know that this information is false and perpetuated.

Anywho, good to know that you have to pull the fuse and NOT the relay.

Carry on.

 

[cbr900boy]

Yep. Whoever wrote that article is an idiot. It wouldn't make sense for the volatile memory to be connected to the EFI relay because it would be erased every time the relay cycled. You have to pull the fuse.

Is there any difference between pulling the fuse and disconnecting the negative battery terminal? I've always just disconnected the terminal.

 

[SpidermanGeek]

Is there any difference between pulling the fuse and disconnecting the negative battery terminal? I've always just disconnected the terminal.

Obviously, I'm no expert... but disconnecting the battery for 30 minutes would also reset things like the clock and radio presets and that kind of thing, no?

 

[TheDurk]

Although, in an older post relating to the EFI fuse/relay, you can be quoted as having said the following:



That's why I thought that pulling either would do the trick.

Shouldn't somebody amend the buyer's guide?

Because I always thought you had to pull the relay for 30 minutes. And I've done so on a few occasions after some maintenance. And that's not the only spot on T4R that the relay is referenced. I would hate to know that this information is false and perpetuated.

Anywho, good to know that you have to pull the fuse and NOT the relay.

Carry on.

I should have thought longer than two seconds when I wrote that. No excuse other than not thinking about it at that moment, since I've certainly never tried to do it that way and didn't recommend doing it that way.

30 minutes is way overkill. I'd say two minutes is more than enough to clear the volatile memory. Pretty sure it clears the CEL register in that time and that's the same memory. There is no difference in pulling the neg batt cable, except that that will eff your radio and clock, too.


I have edited my 2014 post and I apologize to the community for hip-shooting that one.

 

[tonytoshiba]

Is there any difference between pulling the fuse and disconnecting the negative battery terminal? I've always just disconnected the terminal.

Disconnecting the negative post on battery will reset the EFI. It will also cause the loss of correct clock time. My radio presets have always remained the same, I saved them prior to disconnecting the first time as I have stations for around the country.
My vehicle is 2012 Trail

 

[Rileyismydog]

I just pulled my EFI relay after getting home from work. I let it set for 30 minutes, as suggested. I installed the relay and... nothing. Cranks but no start. Did I just kill this 1998 4Runner? Waiting on a new relay to arrive to see if that fixes it. Any, and all help is appreciated. BTW, vehicle ran fine prior to this.

 

[octanejunkie]

I just pulled my EFI relay after getting home from work. I let it set for 30 minutes, as suggested. I installed the relay and... nothing. Cranks but no start. Did I just kill this 1998 4Runner? Waiting on a new relay to arrive to see if that fixes it. Any, and all help is appreciated. BTW, vehicle ran fine prior to this.

Check the EFI fuse, make sure it didn't pop.

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