Sorry to beat what must seem like a "dead horse".

I was reading through some old threads (OMG YES I USED THE SEARCH BUTTON) and I know about the following ways to "reset" the ECU:

• Technosquare method
• D/C Negative Terminal for 12+ hours
• D/C Negative Terminal and Mash on the brake pedal 4-5 times (under debate)

My question is: has anyone confirmed that the BRAKE PEDAL method works or does not work? In one thread I was reading, somebody was calling BS on this method but other people insist it works.

My concern is: the d/c negative terminal for 12 hours method takes too long, and the technosquare method (from my understanding, not sure though) only resets CELs but does not "truly" reset the ECU.

Can we get a final answer?

Thanks

Mike

 

I've never heard the one about disconnecting the battery and mashing the brakes. Not sure what that would do because once you disconnect the battery, there's no power to anything so depressing the brake isn't going to be triggering any switches or signals.

 

Once and for all: Disconnect the negative battery terminal, then do anything that would draw electrical power, such as stepping on the brakes (brake lights). This will drain any residual voltage from the circuit. My favorite, which ALWAYS works, is to short betwen the lifted negative cable and the positive terminal still on the battery. Make sure that there are no wires on the negative battery terminal or else...

 

Unless there are some huge capacitors somewhere in the car, there shouldn't be any residual power. If there are small caps somewhere, leakage should take care of them in short order. Not to mention that you have "always on" things like the security system, BCM, clock, etc. that will drain any remaining power.

I think that's an "Z" urban myth like the one we used to hear all the time about the ECU "opening" up more power after you reach 1200, 5000, 10000 miles.

 

The "Technosquare" method is the method listed in the service manual for use when you don't have a Consult-II machine available (which I imagine you don't). It does infact reset the learned fuel value.

 

pedal mash method worked for me

 

As I understand it. It depends on the type of code, error as to which method works.

 

There must be some sort of cap in the ecu if you think about it. If leaving the power disconnected for 24 hours resets the ecu, we know that it has volatile memory and that eventually whatever voltage source is holding the memory runs out and memory is wiped out, hence the reset. It's very unlikely there is a battery and a timer in there waiting for 24 hours to tick off so it can decide to reset, especially since the battery would be a pretty ridiculous maintenance item. FWIW, there is no residual power in the car harness once the battery is disconnected, so we know there is no external cap to account for this 24 hour wait. The other peripherals would not be able to drain stored power from the ecu if it is internal to the ecu, it would be isolated. It makes all the sense in the world for a car computer to filter it's input power since it is an electrically noisy environment, and it makes all the sense in the world for it to go to a low power mode when the ignition is off, so those filter caps could store a charge when the batt is disconnected since it should already be in a standby mode and not sucking much current at all. So yes, there must be a capacitive charge stored in the ecu.

And yes to my experience you can drain it real fast by disconnecting the neg batt terminal and pumping the brakes several times. Try it.

edit to add: undrgnd has half a point here, I think the only things that will speed this up are things that the ecu might care about. I think all that happens with the brake pedal method is the ecu gets an interupt telling it to wake up, we're doing something you care about and it tries to run and sucks it's caps dry, boom reset ecu. You would have to do something that the ecu would be listening for for this to work, in other words opening the door wouldn't work even though the dome light would draw power if the batt was connected, but the ecu wouldn't wake from that and nothing would happen that way, same with turning on the headlights, or some other electrical drains.

 

You are correct that the ECU has some sort of capacitor in there to hold enough power to retain it's memory. Otherwise, settings would be lost every time you disconnected the battery to do any work on the car. It's like your basic home clock radio, you can unplug a lot of them for a few minutes and when you plug them back in, the time is correct. Leave it unplugged all night long and it comes back on with the blinking 12:00.

As for the ECU, it doesn't make sense than any external loads would cause it to reset prematurely, otherwise when you worked on the car with the battery disconnected, it would be to easy to drain all the power and accidently reset it.

Of course, the million dollar question is - how do you know your ECU has been reset? I'm not talking about clearing a CEL or some other condition, I'm talking a true reset so that the ECU is relearning mods, etc.

 

The ECU IS reset every time you disconnect the battery to work on it. Settings are stored in non-volatile memory and hence it doesn't care about power. The error codes, including the pending ones are lost whenever power is removed form the ECU for the appropriate length of time.

 

lol, yeah that is the $1M question isn't it? I could tell you it was much livelier, but that is too subjective and not concrete, but it is what I felt. I'd been driving around for a while in pretty tight traffic, not able to push the car and it seemed like the car was in econo mode. I tried that reset method out of curiousity and I believe I got some power back, but yeah, no solid evidence for you. FWIW, I was a doubter about the whole ecu reset thing in general, not just this method. I was pretty convinced that despite the car having a "learning" ecu that when I needed the power it would give it to me when it sensed WOT. Not the frist few times while in econo mode though, now I just try not to let it get to that place.

I guess the real way to chase this home would be to get someone doing a decently drastic N/A mod to try this immediately after some driving to baseline un-reset ecu, check things out again for a few hours after the brake/batt deal, and then disconnect for 24-hours and compare once more. I'll be doing a plenum myself as soon as we hear something more from motordyne regarding the best combo of their stuff, V2 or not, for a rev-up. Heh, of course if we could really use somebody doing something like that say, right now, to jump in here.

 

So, let me get this straight.

Let's say for the sake of argument, you have a CEL showing but you're certain it will go away if the ECU is reset.

If you D/C your negative terminal for too short a period of time, does the CEL go away or not go away?

The test is: next person who gets a CEL / SES light needs to disconnect the negative terminal for a few mins then reconnect and see what happens.

If the light doesn't go away, disconnect the negative terminal again and mash the brake pedal a few times. Then see, again, does the light go away?

I'm frankly a little surprised no one has a crystal clear answer on this.

 

Yeah, I'm pretty certain it works myself, just from my own limited experience, but DavesZ#3 had an excellent point. It's not like you get any blinky lights to tell you it's done. Your CEL/SES test may show something for us. FWIW it was one of the vendor reps in a post tipping to use this way that got me to try it. I'm almost certain it was Tony at Motordyne, you ought to ping him on this.

edited for spelling, damn tough day!

 

d/c negative terminals + steppin on the brakes worked for me.

It's not a big deal but the car just runs leaner. Felt a lil stronger

 

aight i installed a popcharger but did not reset me ecu...is that ok or should i reset it?

 

Did you get a check engine light?

 

SUCCESS! disconnect negative terminal from battery then pumped the brakes a couple times then plugged the battery back up and ecu reset! I had a bad mass air flow sensor and seems to have fixed the service engine light

 

ECU RESET:

1. Confirm that accelerator pedal is fully released, turn ignition switch "ON" and wait 3 seconds.

2. Repeat the following steps (a and b) procedures quickly five times within 5 seconds:
--a. Fully depress the accelerator pedal (HARD).
--b. Fully release the accelerator pedal.

3. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 10 seconds until the CEL starts blinking.

4. Fully release the accelerator pedal (while the CEL is still blinking)

5. Wait about 10 seconds.

6. Fully depress the accelerator pedal and keep it for more than 10 seconds.

7. Fully release the accelerator pedal (The CEL light will continue to blink).

8. Turn ignition switch to "OFF" position and now you can start the car. The CEL light should be gone.

 

I hate this method--again, you have no feedback whether or not you were successful because the SES light keeps blinking. I've been able to get this to work on the third try, sometimes the fourth, but usually, it takes about 20 tries. What a PITA.

Gotta love the OBDI guys who could simply pull a fuse.

 

I get it on the first try

guess you need to practice your timing