Here is how to reset your ECU without disconnecting your battery. This is a solution for those who install new parts and do not want to risk losing their trip meter mileages, radio presents, and so on. Make sure the car is off and that the key is not in the ignition.
Open the hood and locate the "Engine Room Relay Box." This is the fuse/relay box in the engine bay. On the xA/xB, it is the black top box to the right of the engine bay.
Take the black cover off and flip it over to read the embossed diagram. You want to look for the EFI fuse (not RELAY). On the xA/xB, the EFI fuse is 15 Amps. On the tC, the EFI fuse is 20 Amps.
On the xA, the EFI fuse is #4:
http://www.scionlife.com/tech/images/ecu_reset/efi-xa.gif

On the xB, the EFI fuse is #12:
http://www.scionlife.com/tech/images/ecu_reset/efi-xb.gif
Using the fuse-puller (white piece of plastic in the box), pull the EFI fuse out and let it sit for 10-30 seconds.
Pop the fuse back in the EFI fuse socket. Make sure it is properly seated and is uniform with the other fuses.
Put the black cover back on.
Cross your fingers, start up the car, and hope you don't pull another CEL (Check Engine Light).
If you are successful in not pulling a CEL, I recommend you let the car for 5-10 minutes for good measure.

Some people have told me this does not work on the tC. Whether or not they did it right is beyond me. This has worked with other cars... If someone can get back to me on this, that would be very helpful.
Update:
Mikochu, in the unlikely event that you are still monitoring this post, this fix 100% works for the tc. I used it this weekend when installing a SRI. Thanks!

wouldn't it be faster and easier to disconnect the battery since you're under the hood anyways?

thanks for the info mikochu ...... :D

oh tyte. i've been wondering which fuse it is to reset. thanks!

i like the fuse method better than the battery-disconnect method; pulling out a fuse can be done without busting out my toolbox.

wouldn't it be faster and easier to disconnect the battery since you're under the hood anyways?

Ummmmm here is the reason why some don't disconnect the battery.

This is a solution for those who install new parts and do not want to risk losing their trip meter mileages, radio presents, and so on.

nice idea
i understood everything and i am fine
but, what you meant by "those who install new parts"?
what parts? like what??

i did it that way when i installed did the poor mans intake mod, i unplugged the maf and then did the fuse thing and it felt as if i lost power ...so i redid it but just unplugged the maf without doing the fuse thing and it pulls much better..... i thought it might have been that i didn't wait enough so i did it a few times and it was that. strange but i am against pulling out your efi fuse from experience!

I read on Consumer Reports:

Obtain a fresh unused 9V battery (those rectangular shape battery). Obtain a 9-Volt Vehicle DC-to-DC Adapter (one end plugs in your cig. lighter; the other end has connection for a 9V battery. Plug the 9V to the adapter> Plug the adapter to the cig lighter. It should work, according to CR.

so if i isntaled an cold air intake and a new exhuast system..then i need to do this right?
i feel that my rpms and motor is running funny.

so if i isntaled an cold air intake and a new exhuast system..then i need to do this right?
i feel that my rpms and motor is running funny.
Definitely after a CAI install...

ok i just gave it a try... CEL has not come on yet.. going to let it run for a the time you say to.

hmm seemed to clear up a few problems if it is the same in the morning il have to make the sure the CAL is set right and screws are tight and no air leaks.

mikochu thank you for this info.

If you dont do it after CAI install what will happen?

umm...this came in handy yesterday unforunately i read it today..

nice idea
i understood everything and i am fine
but, what you meant by "those who install new parts"?
what parts? like what??

after any install of aftermarket parts all the parts need to be recalibrated in order for your or any computer ran car to run its most efficient. things such as fuel maps air for sensors and such need to be recalibrated and the only way to do so properly is to reset you ECU after a install or mod and drive the car normally until the car has gotten a chance to set all the settings to correspond with the new modificatons or installation.

^^^ does that include things like carbon fiber door sill plates? :P I

Mikochu, in the unlikely event that you are still monitoring this post, this fix 100% works for the tc. I used it this weekend when installing a SRI. Thanks!

Is there anyway to be sure the ECU reset after doing this?

Is there anyway to be sure the ECU reset after doing this?
Well, I can 100% vouch for this working on the TC. I had a CEL on mine before I did this , and rather than disconnecting the battery, I decided I'd see if this method worked. Pulling that fuse removed the CEL, so yeah, it works :)

Is there anyway to be sure the ECU reset after doing this?
Well, I can 100% vouch for this working on the TC. I had a CEL on mine before I did this , and rather than disconnecting the battery, I decided I'd see if this method worked. Pulling that fuse removed the CEL, so yeah, it works :)

Oh, thanks! Although, I was actually looking for some kind of "landmark" that I could look for after reseting it to assure me that I did it right. I'm installing a CAI so I'm guessing a power gain would be something to lookout for. I'm guessing that If the engine doesn't run well anymore or my gas mileage dramatically drops...I can tell the ecu didn't reset....???

Oh, thanks! Although, I was actually looking for some kind of "landmark" that I could look for after reseting it to assure me that I did it right. I'm installing a CAI so I'm guessing a power gain would be something to lookout for. I'm guessing that If the engine doesn't run well anymore or my gas mileage dramatically drops...I can tell the ecu didn't reset....???

There really isn't any kind of landmark or anything. But trust me, if you pull that fuse at the beginning, and leave it out until you are done, the ECU will be reset.

Just remember to let the car idle for 5-10 minutes before you drive it. Regarding Gas mileage....most likely your first two tanks are gonna be significantly lower...I say that because when you hear how aggressive the new intake is, you're gonna jamming the gas all the time, and winding it up. I typically averaged about 23-24 or so in town, prior to the intake. MY first two tanks after wards were 20.x But that's because I was shifting at 4-5000 rpm's, not 2800. Once I got over the noise/aggressiveness, the gas mileage went back up to 23 ish.

Oh, thanks! Although, I was actually looking for some kind of "landmark" that I could look for after reseting it to assure me that I did it right. I'm installing a CAI so I'm guessing a power gain would be something to lookout for. I'm guessing that If the engine doesn't run well anymore or my gas mileage dramatically drops...I can tell the ecu didn't reset....???

There really isn't any kind of landmark or anything. But trust me, if you pull that fuse at the beginning, and leave it out until you are done, the ECU will be reset.

Just remember to let the car idle for 5-10 minutes before you drive it. Regarding Gas mileage....most likely your first two tanks are gonna be significantly lower...I say that because when you hear how aggressive the new intake is, you're gonna jamming the gas all the time, and winding it up. I typically averaged about 23-24 or so in town, prior to the intake. MY first two tanks after wards were 20.x But that's because I was shifting at 4-5000 rpm's, not 2800. Once I got over the noise/aggressiveness, the gas mileage went back up to 23 ish.

Thanks! GREAT FEEDBACK!

Glad to be of help :)

I installed mine the other day and used this method to reset the ecu. If I had done it wrong and it didn't reset for any reason the CEL would've lit up right?

I'm pretty sure, yes.

It worked like a charm...it's been running great! I was a little sceptic at first. Now, if there would be a diagram for the tc, I'm sure that would help out future installers alot. THANKS FOR THE HELP EVERYONE!

can some explain why it's the EFI fuse and not the ECU-B fuse on the tC?

Good info, i've tried before but never noticed a difference...but trying it after doing a few more things - def a difference. Good write up!!!

well i just want to know what EFI fuse # for tC??

other than that very helpful info :bow:

Aewsome post! I just changed to a K&N drop in filter and it caused a CEL. I knew there was a way to reset the ECU without loosing the clock, radio settings and such.

Thanks!!!

cool i'll have to pull the fuse when i put in my CAI

good write up

I have a tC and I did this twice. I looked at the back of the fuse box for the efi fuse. There are only two 20 fuses so you have to make sure you look at the fuse chart on the top where you got the fuse clips from. Then I took the fuse out and put it back in 20 seconds later. When I turned my car on it did not fix the cel issue. The second time I took it out I cleaned my car and then put it back in. Either it takes a few times to take it out or it has to be out longer. Someone that has a tC I would give it 10-15minutes then put it back in. See if that fixes the problem the first time.

Here is how to reset your ECU without disconnecting your battery...
On the xA, the EFI fuse is #4:
On the xB, the EFI fuse is #12:
...

That is from the first post of this thread, and I think the fusebox diagrams are switched (interchanged). The first fusebox is the really xB's and the second fusebox is really the xA's. I don't think anyone has noticed this error yet.

I think the post would be correct if the diagrams were left in the same place and only this change was made:

On the xB, the EFI fuse is #4:
On the xA, the EFI fuse is #12:

Otherwise, my xB has an xA fusebox ;-)

[

On the xB, the EFI fuse is #4:
On the xA, the EFI fuse is #12:

Otherwise, my xB has an xA fusebox ;-)

It's #4on my 2005 xA RS1.0. I had to reset the ECU 6 times after installing a K&N filter.

[

On the xB, the EFI fuse is #4:
On the xA, the EFI fuse is #12:

Otherwise, my xB has an xA fusebox ;-)

It's #4on my 2005 xA RS1.0. I had to reset the ECU 6 times after installing a K&N filter.

Yes, I was not correcting the fuse numbers for either car. I was noting that the diagrams were transposed.

How did you know that you needed to reset the ECU even one time??

After I reset my ECU by pulling the #4 fuse, I just started up, warmed the engine for a mile, and then started winding it out in each gear at full throttle. To let the ECU educate itself about 93 octane, supposedly.

It accelerated so violently in 2nd I couldn't find the little tachometer in time to avoid 6000 rpm LOL.

[quote="vintage42"]

How did you know that you needed to reset the ECU even one time??

Itquote]

When I added the K&N it would throw a CEL (check engine light) which also deactivates the VSC abd ABS. Because the K&N is oiled the oil gets on the MAF and causes the CEL. After about 5 resets and spraying electronic cleaner on the MAF sensor the CELs went away.

Anytime you add an engine, intake or exhaust perfromance part you should reset the ECU.

My VSC, Trac Off and Check Engine lights came on today for no apparent reason. I pulled the fuse for one minute replaced it and started the car and all is well. Great write-up.

I have to agree it was a good write up. Does anyone know what makes the car do this though??

can someone clarify what fuse to take out for the tc? after installing my CAI, my car still feels the same as stock... will pulling out the fuse help fix it?

yes please verify what fuse # it is that you pull out of the tc

ive also heard that if you have your stock headers cat, to knock out a piece of the catalyst and put it between the 2 antifowlers, but sense i dont have the cat, would there be anything else that could work just as well as the catalyst?

tC

http://tijil.org/tC_fuse_EFI.gif

HTH,
Tomas

Thanks Tomas. I <3 U.

just for the sake of posting it, my manual for my automatic (06) xB sayd 5. EFI 15 A:.....

so in other words, the FI on 06 xBs #5, not #4 which was initially posted.

#4 is DOME 15 A........

thought it should be said.....

The manuals show the fuses as different random numbers - the numbers are just to identify the words with the pictures. Is the position of the fuse the same or different?

Tom

Actual pictures would be really nice, whiever has them. Kinda don't wanna f*ck this up

bringing the thread back from the past... but thanks for the info... i'm dealing with a CEL and my car stuck in emergency mode that I can't clear... so i'm hoping the fuse pulling method works!!! :relief:

I reseted the ECU by disconnecting the battery, it worked but now the passenger window is not working from the pilot control, do you know something??

I reseted the ECU by disconnecting the battery, it worked but now the passenger window is not working from the pilot control, do you know something??

Is the light on the window switch blinking? If so:

From the drivers door, roll down the window, keep holding the button for 5 seconds after being down. Roll it back up and hold again for 5 seconds. You have to re-initialize the windows.

If not, take it to your dealer.

i didnt notice that they were blinking, yes it worked, thank you very helpful

be aware, im not sure if it was mentioned but your car computer (ECU) has to relearn everything, on a automatic it relearns the gears and shift points, it also relearns timing and fuel along with a lot of other things. 10 miles at 2200rpm with ac off same with ac on idle for 20 minutes (until its fully relearns) So i would not be going like a bad out of hell if you have a turbo or sc, as it will probably lean the hell out of you in some areas while its relearning the map.

Food for thoughts! Great Write Up!

be aware, im not sure if it was mentioned but your car computer (ECU) has to relearn everything, on a automatic it relearns the gears and shift points, it also relearns timing and fuel along with a lot of other thingsUp! The ECU does not learn, remember, forget, unlearn or relearn. It operates in real time using the inputs from the engine's sensors such as MAF, O2, knock.

The ECU does not control the automatic transmission. If the automatic transmission is electronic like my Subaru's, it is controlled by a separate TCU that does continuously modify when to shift for the way it has most recently been drive. But I don't think the Scion automatic transmission is electronically controlled so has no TCU.

The ECU does not learn, remember, forget, unlearn or relearn. It operates in real time using the inputs from the engine's sensors such as MAF, O2, knock.

The ECU does not control the automatic transmission. If the automatic transmission is electronic like my Subaru's, it is controlled by a separate TCU that does continuously modify when to shift for the way it has most recently been drive. But I don't think the Scion automatic transmission is electronically controlled so has no TCU.

Don't guess, know. :eyebrow:

Scion ECU (ECM) black boxes DO learn over time based on long term driving habits, and set one of several different performance modes for engine and transmission. This same "long term" adjustment (memory) is actually lost, and has to be relearned, when power is removed from the ECM...

Here's the wiring diagram for the Electronically Controlled Transmission in the xB Classic:

Automatic Transmission Control (http://scionlife.org/Scion_Docs/2004_xB_Shop_Manuals/2004%20xB%20Wiring%20Manual/H_systemcircuits/AutoTransCont.pdf)

Note that the electronically controlled transmission is directly controlled by the Engine Control Module (ECM/ECU)...

Read especially the last bit that describes in simple English how the ECM controls the transmission.

Yes, that is the same ECM that is reset and has to relearn from scratch through several complete cycles how it's driver drives, and sets engine and transmission to match that "style." Yes, the ECM also adjust and controls "real time" as events happen, but it also adjusts over a much longer period to a number of overall driving habits.

The box is much more sophisticated than most people give it credit for being...

http://tijil.org/bb-smob03.gif

I should have been less certain and said if the transmission was electronically controlled it would learn. So the transmission is electronically controlled and can adjust to drivers, like the Subaru. You then indicate that the ECU also learns for the engine, but the link does not say that.

Are you also saying that the ECU also learns, remembers, forgets, unlearns and relearns the running of the engine? Rather than operating in real time using the inputs from the engine's sensors such as MAF, O2, knock? Are you contributing to the impression that the ECU must learn how to run the engine from the driver? Where do you get this from?

Do you also advocate disconnecting the battery to reset the ECU when changing octane, air filter, spark plugs or muffler? Do dealers know about this? Does the owners manual mention it?

I should have been less certain and said if the transmission was electronically controlled it would learn. So the transmission is electronically controlled and can adjust to drivers, like the Subaru. You then indicate that the ECU also learns for the engine, but the link does not say that.

Are you also saying that the ECU also learns, remembers, forgets, unlearns and relearns the running of the engine? Rather than operating in real time using the inputs from the engine's sensors such as MAF, O2, knock? Are you contributing to the impression that the ECU must learn how to run the engine from the driver?

Do you advocate disconnecting the battery to reset the ECU when changing octane, air filter, spark plugs or muffler? Do dealers know about this? Does the owners manual mention it?

I'm not advocating anything, Allan, only correcting the misinformation you provided.

There are, to my understanding, two different sets of adjustments made by the ECM both for the engine and the transmission: Short term and long term.

Obviously both engine and transmission respond and make adjustments based on current inputs, but it is my understanding that these instant changes are also moderated by long term trends that the ECM learns over time. Exactly what these trends are and how they interact with current inputs are very cloudy, and they are a proprietary feature of the Toyota firmware.

The background information originally provided to the sales organization when these vehicles were introduced did state that both engine and transmission responses were modified by not just current inputs, but by learned habits. I'm much more inclined to accept the word of the folks who developed the hardware and firmware than I am the word of someone who said the ECM didn't even control the transmission.

Should you find reliable info that says something contrary, you are certainly more than welcome to present it. :)

(I believe the experience of the forced induction folks will also reinforce the idea that the ECM learns over time and makes long-term engine adjustments, as one of the "problems" some encounter appears to be trend adjustments made by the ECM...)

From the ECM description... (http://scionlife.org/Scion_Docs/2004_xB_Shop_Manuals/2004%20xB%20Wiring%20Manual/H_systemcircuits/EngineControl.pdf)

Control System
∗ SFI system The SFI system monitors the engine condition through the signals, which are input from each sensor to the engine control module. The best fuel injection volume is decided based on this data and the program memorized by the engine control module, and the control signal is output to TERMINALS #10, #20, #30 and #40 of the engine control module to operate the injector. (Inject the fuel). The SFI system produces control of fuel injection operation by the engine control module in response to the driving conditions.
∗ ESA system The ESA system monitors the engine condition through the signals, which are input to the engine control module from each sensor. The best ignition timing is detected according to this data and the memorized data in the engine control module, and the control signal is output to TERMINALS IGT1, IGT2, IGT3 and IGT4. This signal controls the ignition coil and igniter to provide the best ignition timing for the driving conditions.
∗ IAC system The IAC system increases the RPM and provides idling stability for fast idle–up when the engine is cold and when the idle speed has dropped due to electrical load, etc. The engine control module evaluates the signals from each sensor, outputs current to TERMINAL RSD, and controls the idle air control valve.
∗ Fuel pump control system The engine control module operation outputs to TERMINAL FC and controls the C/OPN relay. Thus controls the fuel pump drive speed in response to conditions.
Emphasis added --Tomas

So is it accurate to say that "your car computer (ECU) has to relearn everything... timing and fuel along with a lot of other things"?
What are the situations where you believe that the ECU should be reset?

So is it accurate to say that "your car computer (ECU) has to relearn everything... timing and fuel along with a lot of other things"?
What are the situations where you believe that the ECU should be reset?

No, the ECM does not have to relearn everything - the vehicle will continue to run adequately with what it currently remembers or with the "average" settings it has when freshly reset, but it can adjust itself to get along better with its usual driver's style if allowed to "customize" it's settings by remembering the conditions it normally encounters.

As to when might I recommend resetting? When any change of vehicle equipment that might affect the engine or transmission customizations that have been made in ECM memory, and that includes change in tire diameter, change in air intake, or other similar changes that will cause a sudden, semi-permanent change in the engine or transmission's operating environment.

Some folks like to reset with change of seasons, but I feel that seasonal changes are certainly gradual enough that the ECM can easily keep up.

Some folks believe it is reasonable idea to reset when one moves to a new area, because changes in altitude and topography require re-learning. There is some good thought in that, and I can see the logic: Why build the new memory on the old, why not just start from scratch with a reset?

Some suggest it for extended vacations in totally different environments. (I would probably not - but at the same time I would not be averse to resetting when I get back home...)

Some even suggest resetting once a year - often in the spring when they go through everything on the car anyway - simply to clear the memory and reboot the ECM computer. Spring cleaning. I can understand the logic in that, too.

All the ECM reset does is erase the customization based on previous experience and bring everything back to factory settings. It might save a little bit of learning time or, more importantly, clear any errors or anomalies that might have crept in. It is akin to rebooting any other computer: It gives it a fresh start without any of the minor errors that might have accumulated over its runtime..

Turning the ignition off does not re-boot the ECM computer - it merely goes into a "sleep" mode - although it does wake up about 5 hours later and run some checks, such as those it does on the fuel system during extended downtime.

A reboot comes most easily from a temporary removal of ECM power (pulling fuse or disconnecting battery), and that is the quickest way to get back to a cleared memory and factory settings.

Many folks do not like to reboot the ECM by disconnecting the battery because other devices in the vehicle also have volatile memories that are lost when this is done (trip odo, radio, etc.).