Hi, I would like to know if there is a way to reset the ECM at home without an HDS or a computer.

 

I had trouble with reduced MPG after the dealer recently "flashed" my PCM with an update. After pulling the - battery cable for a few minutes I did the "idle until the fan comes on twice and wait 10 minutes", starting from a cold engine. My tailpipe is now free of the black soot that became apparent after the PCM update and the MPG is right back over 40 for a trip.

 

Codger dude, I think you have revealed the simple truth. From our experiences and your post I conclude that all the average Fit owner has to do is disconnect the battery, let the engine cool down, then reconnect, startup and let it go through the fan cycles as you report. It's that simple. No voodoo magic required. It has always resulted in my car running perfectly.

 

Just had the procedure done yesterday, it's really hard to hear the cooling fan and no, I'm no deaf

Ciao,

 

I reinstalled ECU after the Hondata reflash that is part of the KWSC high boost upgrade and took off on a drive without doing the idle relearn procedure and was very bummed out over the amount my fuel gauge needle moved.... I did the process before filling the tank and there appears to be a difference but I really won't know until I fill up again and even then the extra boost and tuning changes will probably have a negative effect on fuel mileage..... I am hoping that using my throttle controller in the eco5 mode and position will have some influence in keeping fuel cost down.

 

This may be a stupid question, but I'm new to this ECM/Idle Learn stuff. I drive a 2008 Manual Fit Sport and currently have 56K miles. About 5K miles ago my stock tires were shot so I threw on an extra set of 17s that I had laying around the house until I could get the funds for new 15in tires. Prior to the 17s, I was averaging 35-37mpg. After installing the 17s I noticed quite a drop in gas mileage which was expected due to the increase in weight. It dropped to an average of 30mpg. Also, my registration expired during this time so I had to go get the emissions testing done to renew it. They of course disconnected my scangauge so after reconnecting it I then had to recalibrate it on the next tank fillup. So, this past week I finally got my stockies back on with new rubber and was excited to get back at 35-37mpg but I've had no such luck.....still consistently getting 30mpg??? Do I need to have the dealer reset something or try this idle learn thing? I'm not just going by the scangauge, I'm also calculating it via fillup amount/mileage. Any thoughts?

 

Do this,

Disconnect your battery for 20 minutes

then follow these directions:

1. turn the ignition switch ON (II), and wait 2 seconds.

2. Start the engine. Hold the engine speed at 3,000 rpm without load (in park or neutral) until the radiator fan comes on, or until the engine coolant temperature reaches 194 F (90 C).

3. let the engine idle for about 5 minutes with the throttle closed. (NOTE: if the fan comes on, do not include its running time in the 5 minutes.)

This will complete the reset. You can then turn off your car.

Make sure to have your radio code as disconnecting your battery will cause you to have to reenter it.

Your gas mileage problems might not be fixed by this, but it shouldn't hurt. You mainly do an ecm/pcm reset when you alter the intake or exhaust system, not really sure if it affects the tires.

 

I would agree. Let us know how it works.

 

If you aren't topping off the tank when refueling and relying on the fuel pump cut off instead it could be affecting your mileage figures.... I get better than 30 MPG running 10 PSI boost and richer fuel mixture than stock if I can control my right foot.

 

How would topping off the tank increase my mileage? I go to the same gas station each time and reset my odometer then when I return to fill-up I pump until it clicks everytime and just divide the mileage by the number of gallons used. Unless the fuel pump cutoff clicks at different amounts I don't see how that could be the problem, only maybe if it was 2 different gas stations.

 

For a LEV-2 car my 2008 tailpipe tip has lots of soot on it. I will give this a trip and see if it helps.

 

Hi there all! I just wanted to put my two cents on the subject.

I recently added an air intake, and while I contemplated on doing the idle reset at that point, the car was running just as well as before. With a PRM intake, I suppose I should've been expecting more.

After performing a transmission fluid flush, I was driving the car and was wondering why the car was hesitating shifting from third to forth with half throttle applied. I thought I killed my trans from flushing!

Anywho, I decided to do an idle reset. I disconnected the battery for 2 minutes, plugged it back in, and started the car. I waited 2-3 minutes on idle, but I figure to get the fan running, it would've taken a while. My dad watched for the radiator fan to turn on with his flashlight (just did this about 11 pm EST) while I held the engine at 3K rpm.

When the fan kicked in, I waited until it was done and waited for 5 minutes. The fan kicked in a second time. I waited another 5 minutes. After that, the fan turned on a third time. Once that was done, I waited for it to finish and turned the car off.

Grabed my wallet and phone (juust in case), and took a test drive with Dad on a local highway.

Shifting was remarkably tighter, more consistent, and felt like the shifting when I bought it brand new. The hesitation and slight whine at third gear was gone, and got me up to 5.5k RPM when it gave a very satisfying shift up to 4th with quite a lot of power to spare. Throttle response was more apparent, and I got a much stronger growl from the PRM intake.

With 33K miles on my car for the 2007 GD3 Fit Sport, I feel very confident that this idle technique is key for anything major regarding any intake or exhaust change. The transmission fluid change I recommend be done for anyone every 30K, since my fluid did end up looking brown (I'm doing mixed city/hwy driving, mostly 50-65 mph drives for 8 mile bursts at a time with some bumper to bumper traffic).

With all this information, I hope that future readers will be confident in this procedure. I know that I have!

 

Hey, great news! And glad to see another satisfied PRM customer. I still love my GD3 intake after a year.

 

I know this is super old but I want to try this for rough idle I'm running out of ideas.

This may seem like a dumb question. When you disconnect the negative cable is the engine supposed to be off it running?

Thanks in advance.

 

Engine not running. Off.

 

Perfect, thanks a ton!

 

Usually how long does it take for the fans to come on?

 

It can take awhile - like 15 minutes, or less. But no worries, if you are patient, they will come on. So I D/C the battery for 30 minutes (old school), start the engine and just find other things to do while I wait for the fans to come on. Then wait 4 fan cycles through and it's always sweet.

 

Most vehicles, if you disconnect battery negative and turn on the ignition key for a minute it clears the ECU almost immediately.

 

I don't doubt it. good to know.