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Old 04-30-2013, 10:49 AM   #1
gggplaya
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Default Recalibrate Accelerator Pedal Position Sensor?

I recently had work done on my car. They disconnected my battery as evident by needing to reprogram all my radio stations. When i left the shop the car stalled and died a few times while slowing for stop lights. I had to rev it a few times and it seemed as if the car was learning how much throttle it needed to give. That was a week ago and now the car seems to run fine, except it doesn't seem to give enough throttle when cruising off the pedal. Sometimes the car jerks back and forth if i don't give it just a little gas.

Is there a procedure to properly re-calibrate the throttle by wire system?

i have a 2008 impreza 2.5i 5MT.
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Old 04-30-2013, 11:22 AM   #2
Rudgers73
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I have had the same problem with my car after disconnecting the battery for a while. The electronic throttle needs to relearn. I struggled for a week just trying to deal with it but it never got better. There is only one way to reset it properly and it takes about 20 min.

Your car must be cold for this to work:

1. Get in your car and make sure all of the accessories are off (A/C, lights, radio, fan, etc)

2. Turn the key to the "On" position and wait for 20 seconds. You should here some relays and your fuel pump for a second.

3. Start your car without touching the gas petal.

4. Let it idle until the radiator fan comes on.

5. Turn off the car and when you restart you should be all set
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Old 04-30-2013, 11:55 AM   #3
gggplaya
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Should i disconnect the battery before starting all this?
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Old 04-30-2013, 01:53 PM   #4
gggplaya
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Quote:
Originally Posted by Rudgers73 View Post
I have had the same problem with my car after disconnecting the battery for a while. The electronic throttle needs to relearn. I struggled for a week just trying to deal with it but it never got better. There is only one way to reset it properly and it takes about 20 min.

Your car must be cold for this to work:

1. Get in your car and make sure all of the accessories are off (A/C, lights, radio, fan, etc)

2. Turn the key to the "On" position and wait for 20 seconds. You should here some relays and your fuel pump for a second.

3. Start your car without touching the gas petal.

4. Let it idle until the radiator fan comes on.

5. Turn off the car and when you restart you should be all set
Ok so i went and did it during my lunch break.

1. I first disconnected the battery, waited a minute or 2, pressed on the brake to get rid of any energy in the system. Then reconnected the battery.

2. Then i keyed on and waited for 20 seconds. I pressed on the gas pedal slowly from full off to full throttle. I did this 4 times so the ecu could learn the full range.

3. Then i started the engine and let it idle for about 10 minutes. (You'll see the rpms jump to about 1300rpm, then slowly work it's way down to 700rpm. It'll flucuate alot as it learns how to maintain rpm's. It'll flucuate alot at 700rpm until it learns how to maintain it.)

4. Once the tach is holding steady at 700rpm, i let it run for a few more minutes just to be sure it's good.

5. Then with the car in neutral and the parking brake on, i slowly began to increment the throttle. Start with 2mm, let the car try to hold the rpm steady, it'll fluctuate alot until it learns, then continue to the next 2mm increment until the car can hold the rpm steady. I did this until it reached about 3000rpm.

6. Repeat step 5 a few times to make sure it's consistent and learns the subtleties of slight throttle.

7. Take it out for a drive, it still has some learning to do, just drive as normal at first until it seems smooth.



Now it's much improved. No more jerking back and forth while cruising off throttle. The shifts are also smoother because it gives it some actual gas between shifts. Seems like it's back to factory when i first got it. I wish subaru published an actual calibration procedure like when it leaves the assembly line. I have the tech manual, but can only find the voltages for the pedal, nothing about calibration.
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Old 04-30-2013, 04:15 PM   #5
Rudgers73
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looks like you may have added a few unnecessary steps (the incremental stepping while the engine is running) but if it worked for you then no biggie!

good deal

I think the biggest part of the recalibration is the stepper motor knowing where the home position should be during idle. I think the rest is just a span to WOT which is a pretty big window with the standard definitions in the table.
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Old 04-30-2013, 05:33 PM   #6
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I have a 2008, the computer programming may be different than your 2006, but it most definitely needed the incremental revving. It was having trouble maintaining rpm at each increment, you could see and hear the engine trying to figure it out. Now i can do it and it holds steady at each increment.

My biggest issues were the jerking off throttle which was very annoying, and light throttle sensitivity which was tolerable(give it more gas). It just seemed like i needed to push the pedal down more than i was used to. It just didn't seem to give it enough gas with light throttle and it wasn't consistent like when i bought the car.
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Old 04-30-2013, 06:17 PM   #7
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Oh interesting. Glad to hear you are good to go
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Old 05-02-2013, 10:49 AM   #8
tauntaun
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Would this same procedure work on my 2001 wagon? I know the battery had been replaced recently and it has the same symptoms you describe above.
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Old 05-02-2013, 10:55 AM   #9
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Double Post
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Old 05-02-2013, 10:56 AM   #10
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Originally Posted by tauntaun View Post
Would this same procedure work on my 2001 wagon? I know the battery had been replaced recently and it has the same symptoms you describe above.
I'm not sure, but it doesn't hurt to try, and only takes 20 minutes of your time.

On throttle by wire cars, it very apparent the need to relearn everything. The engine stalls if you simply try to drive off, and it has trouble maintaining rpm with no engine load. It's never been like this on any of my other cars, but they are all cable throttle.
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Old 09-17-2013, 09:14 AM   #11
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I will have to try this..I have an 06 Baja that I just bought. When I hooked up the scan tool, it was reporting a TPS reading of 15% at closed throttle and 74% at WOT.
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Old 09-17-2013, 03:22 PM   #12
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Quote:
Originally Posted by compu829 View Post
I will have to try this..I have an 06 Baja that I just bought. When I hooked up the scan tool, it was reporting a TPS reading of 15% at closed throttle and 74% at WOT.
Was that with Engine running and driving or just key on?

There is more that goes into final throttle plate angle than just the acceleration pedal position. It calculates what the engineers have decided is the best throttle angle based on, at the least, Engine speed, Engine load, accelerator pedal position. On an automatic transmission equipped vehicle it may use other parameters in addition to the three I listed to determine final throttle plate angle.
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Old 09-17-2013, 09:02 PM   #13
Rudgers73
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Quote:
Originally Posted by compu829 View Post
I will have to try this..I have an 06 Baja that I just bought. When I hooked up the scan tool, it was reporting a TPS reading of 15% at closed throttle and 74% at WOT.
15% at idle may be correct. It's designed to "limp" with a broken servo motor... 15% would keep you from stalling with a smooth clutch application
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