('03-'05) Electronic Throttle not responding - Subaru Forester Owners Forum
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post #1 of 9 (permalink) Old 03-09-2011, 05:51 PM Thread Starter
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Car Year: 2005
Car Model: Forester 2.5X AT
Unhappy Electronic Throttle not responding

HELP! I have an intermittent (but almost daily) problem with the electronic throttle not responding on my '05 Forester 2.5X with auto trans. Often I stop ata red light & when I stepon the accelerator the engine doesn't rev normally. It has a loping idle between 800 & 1000 rpm. When I step on the gas pedal the engine slowly revs up to 1500 rpm. Check engine light comes on & cruise control light flashes.

My OBDII scanner pulled two error codes: P2109 "Throttle / Pedal Position Sensor A Minimum Stop Performance" & P0638 "Throttle Actuator Control Range / Performance (Bank 1).

After I shut off the engine & turn it on a few times, the engine revs normally. It then drives normally for a day or so. I think the problem is in the "throttle-by-wire" system.

Any recommendations on where to start? The throttle position sensor / throttle actuator & the throttle body appear to be one unit that sells for around $570ish new. I was planning to take it off intake manifold & clean everything (I have new gasket). Maybe try to clean sensors on throttle & pedal with electric contact cleaner spray? (How to get to sensors inside plastic boxes???)

Any help is really appreciated!
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post #2 of 9 (permalink) Old 03-10-2011, 03:40 AM
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Has any work been done in the area of the throttle body previously?

I'd first see if the throttle plate moves smoothly. If it doesn't it just needs to be cleaned. Otherwise, you're going to have to start checking voltages of the sensors and connectors, as other than it just sticking, its likely an electrical issue.

04xt/4eat, 16g, STI bits and bobs
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post #3 of 9 (permalink) Old 03-10-2011, 11:47 AM Thread Starter
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Nothing has been done around the throttle body, ever. Subie was in front end collision over a year ago but no problems until now. I did clean the mass air flow sensor at 120K (10K / 6 months ago) with some CRC aerosol cleaner specifically for that purpose. No problems at the time. Just did it as part of 120K service when I had to remove air filter box to change spark plugs.

I have throttle off right now. Throttle plate was pretty dirty on engine side of plate. Cleaned it very well with Subaru throttle plate spray. I was able to get cover off of throttle actuator / sensor box. It is just held on by 6 brass clips. (Hopefully I can get them back on!) Looks clean inside. Sensor appears to be sealed inside plastic cover. Just a plastic non-moving "tab" with tiny lense looking thing that fits into a metal cylinder that rotates when throttle plate moves.

I will clean everything on throttle (including electrical connectors) & put it back together. If that doesn't work?: 1) do same to pedal assembly?, 2) find throttle relay & test?, 3) start testing every wire?!?!

Thanks for the help! Any advise or experience about this type of thing is really appreciated!
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post #4 of 9 (permalink) Old 03-10-2011, 12:09 PM Thread Starter
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Update: cover goes on throttle easily with clips. Rotating cylinder attached to throttle plate appears to have two tiny magnets on opposite sides. Throttle position sensors (I think there are two?) must sense position magnetically.
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post #5 of 9 (permalink) Old 03-10-2011, 06:45 PM Thread Starter
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Where can we find schematics & diagnostic info (voltages, etc.) for Subie throttle-by-wire? I put intake back together & my '05 Forester 2.5X seems to run ok. I will know for sure if it doesn't act up for a few days. Throttle plate wasn't sticking but I cleaned off a layer of gunk (& cleaned electrical connections to throttle). My OBDII scanner indicates the throttle is staying closed a couple degrees more than before (probably because crud gone = a bigger gap for air to get around throttle plate). Was 14.5 degrees at warm idle, now around 12.2 to 12.9 degrees.

I noticed a couple other threads of people with similar issues (& no definite answers). I will try to let you all know if this fixed it or not. Thanks for help.
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post #6 of 9 (permalink) Old 05-19-2011, 11:07 AM Thread Starter
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Unhappy Electronic Throttle good a few months now bad again!

After I had cleaned throttle & connections & put everything back together Subie ran fine for a few months. Last few days it seems like there was a little hestitation when accelerating. This morning I had the exact same problem as before with the same error codes. After Subie was off a few minutes it fired back up & ran normally. I'm checking voltages but don't know exactly what I'm looking for.

Anyone know the following?

Normal percentage of throttle opening at idle when engine is cold / hot?
Which wire is #1, #2, #3 etc on 6 wire throttle plug?
What normal voltages are for these wires?
Where to find wiring diagram or diagnostic info for this?

Also top white wire at plug is the same guage as other wires in plug, but if you peel back the sheath the wire becomes much thicker. I thought thin wire had been crammed into thick wire BUT it came from factory like this (I'm original owner) & tiny bit of wire (shielding?) coming out where thin wire exits thick wire has no voltage while there is 5.02 volts at the plug. Anyone know anything about this?

This intermittent problem is driving me nuts. I love my Subie but can't trust it until real problem is found & fixed. Thanks for all your help!!!
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post #7 of 9 (permalink) Old 11-25-2011, 08:43 AM Thread Starter
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I found the problem!!!

I found the problem!!! Sorry I haven't replyed in a while. It was an intermittent problem with the electrical relay that powers the throttle assembly. I replaced it a few months back & no problems since then. It is a small "can shaped" relay that you can access by removing the glovebox. It is just to the right of the glove box. There are two identical looking relays. One is for the fuel pump. The other (behind the first if I remember correctly) is for the throttle body. I replaced both (since they are relatively cheap & running awfully hot). NO PROBLEMS WITH THROTTLE RESPONSE / ERROR CODES SINCE!!!

When I come across my old paperwork & wiring diagrams I will try to remember to post more details.

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post #8 of 9 (permalink) Old 12-14-2011, 01:33 PM
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Quote:
Originally Posted by BanyanBoy View Post
I found the problem!!! Sorry I haven't replyed in a while. It was an intermittent problem with the electrical relay that powers the throttle assembly. I replaced it a few months back & no problems since then. It is a small "can shaped" relay that you can access by removing the glovebox. It is just to the right of the glove box. There are two identical looking relays. One is for the fuel pump. The other (behind the first if I remember correctly) is for the throttle body. I replaced both (since they are relatively cheap & running awfully hot). NO PROBLEMS WITH THROTTLE RESPONSE / ERROR CODES SINCE!!!

When I come across my old paperwork & wiring diagrams I will try to remember to post more details.

Will you post the part number? I'm getting some P2109 issues, and if the part is cheap I think I'd like to just go ahead and replace it to be sure.

Thanks!
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post #9 of 9 (permalink) Old 10-11-2013, 05:30 PM
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Quote:
Originally Posted by Type2 View Post
Will you post the part number? I'm getting some P2109 issues, and if the part is cheap I think I'd like to just go ahead and replace it to be sure.

Thanks!
82501AA130 for any one in the future.

2004 FXT A/T (vf43 08 STI TMIC)
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