taka Posted May 5, 2014 Share Posted May 5, 2014 I would agree ^^. My TB was, by my experience, pretty darn clean to begin with. I was not confident that my efforts would do anything, but hey, the issue never returned. I chalk it up to a very sensitive system. These cars don't have idler veins, so there must always be a slight and consistent gap at full close which some sludge could interfere with. I couldn't see a reasonable way to get that plastic cap off the TB at all, let alone while on th car. How is/was this done by others? Was that shown to help the problem as well? I did not do that as part of my solution, but I did attempt to blast cleaner up through the butterfly pivot. Link to comment Share on other sites More sharing options...
frank_ster Posted May 5, 2014 Share Posted May 5, 2014 (edited) I would agree ^^. My TB was, by my experience, pretty darn clean to begin with. I was not confident that my efforts would do anything, but hey, the issue never returned. I chalk it up to a very sensitive system. These cars don't have idler veins, so there must always be a slight and consistent gap at full close which some sludge could interfere with. I couldn't see a reasonable way to get that plastic cap off the TB at all, let alone while on th car. How is/was this done by others? Was that shown to help the problem as well? I did not do that as part of my solution, but I did attempt to blast cleaner up through the butterfly pivot. there are metal clips holding the plastic cover on .. its very easy to disassemble in a 2.5 turbo you would probably have to remove the throttlebody to remove the cover. no there are no idle vanes in the throttlebody because it doesnt use a stepper motor or pwm motor. it uses the throttle plate its self for idle control. its default angle when unplugged is slightly open so the car will idle about 1800 rpm so the car can limp home. but again the code refers to a problem between the two sensors with in the throttle body unit where there supposed to be saying the same thing. if there is an argument power is removed from the unit. if the throttle body is not able to close enough it sets a different code i think its excessive idle speed. p2109 Edited May 5, 2014 by frank_ster Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
dragonman586 Posted November 24, 2014 Share Posted November 24, 2014 Hey y'all. I've been experiencing the same issues with a 2.5i. I'll do the recommended cleanings and report back. Link to comment Share on other sites More sharing options...
Kenny Melancon Posted November 25, 2014 Share Posted November 25, 2014 (edited) hi my name is kenny melancon I placed a few notes on here about your code issue, I have fixed my car by cleaning the throttle body no replacement of any parts, I can explain the code to you if you wish , my car has never set the code again. and I have also fixed 4 other cars the same way Edited November 26, 2014 by Kenny Melancon removed my phone number as requested by another person Link to comment Share on other sites More sharing options...
frank_ster Posted November 25, 2014 Share Posted November 25, 2014 you shouldn't put your phone number on the forums .. and what did you clean on the throttle body ? Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
dragonman586 Posted January 5, 2015 Share Posted January 5, 2015 Hello again. The code was thrown at least once a week at the worst. I have changed the entire pedal assembly 3 weeks ago and have not seen the code since. I will update if the code returns. Link to comment Share on other sites More sharing options...
frank_ster Posted January 6, 2015 Share Posted January 6, 2015 can you take the old one apart ? clean it and reinstall it ? it would help us understand what the root cause. the pedal and throttle body are made in a way they dont wear out. the only thing would be contamination that would make it not work. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
emt1581 Posted June 19, 2015 Share Posted June 19, 2015 The 06 Legacy I just bought my wife last Tues night had this code come up. Are there any vids online showing step by step how to dismantle/clean everything? Thanks -Emt1581 Link to comment Share on other sites More sharing options...
taka Posted June 20, 2015 Share Posted June 20, 2015 Not sure about any vids, but feel free to PM me if you have any questions. I have done this before and it is pretty easy. Start with the intercooler off, then the intake piping to the throttle body. Leave the TB on the car so as to not need to replace gaskets. Hose down in cleaner. Careful not to move the butterfly too much - just hold it open and do what you need to. Link to comment Share on other sites More sharing options...
frank_ster Posted June 20, 2015 Share Posted June 20, 2015 (edited) Cleaning the inside of the throttle body may not help anything , this was an issue for carbon on cars with a iac getting stuck. You need to take the plastic cover off the side of the throttle body. If its a non turbo car is very easy . And clean around the magnetic pickup for the throttle position sensor. And put it back together. On turbo car you need to take off the throttle body. The gasket is actually a o ring and they usually dont break. The error code is for missmatch between the 3 different sensors in the throttle plate . Basically if all 3 arnt saying the same thing it sets code and outs car into limp mode. Edited June 20, 2015 by frank_ster Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
emt1581 Posted June 21, 2015 Share Posted June 21, 2015 Update...problem solved! Visited the local Subaru dealer and asked about diagrams/part numbers/ cost of replacement/etc. After talking to a mechanic the guy said he was told I could try to clean the terminals/sensors but usually once the check engine light came on it was time to replace. I was also told about the two 12mm bolts holding the gas pedal in place and the plug connecting everything. Finally, if a replacement was needed it would have been $180 out the door. Came home, unbolted the gas pedal and disconnected the plug. Blew into it...boy was that full of dust!!, then I reconnected everything and started the car....no more check engine light!! Hasn't come back since! Seems like it worked. And if it comes back, I can clean it again or just replace it but I'd find the part online rather than paying $180. Just figured I'd share. Thanks! -Emt1581 Link to comment Share on other sites More sharing options...
frank_ster Posted June 21, 2015 Share Posted June 21, 2015 give it a few weeks Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
Subfan Posted September 5, 2015 Share Posted September 5, 2015 My wife's 2006 2.1i threw this code for the first time today. It went into limp mode 2 blocks from our local Subaru dealer so I took it there. Unfortunately, it is a holiday weekend, so other than reading the code, no-one could look at it until Tuesday (so it is sitting in their shop). I read a little about this, it seems that there are some fixes but most seem to be temporary. I'm not one for typically working on my own vehicle, so I'm pretty sure I'll let the dealership fix for me. I guess my question is, what should I expect them to come back with? Replace the pedal assembly? Or just a sensor? Any idea what I should expect to pay? Link to comment Share on other sites More sharing options...
frank_ster Posted September 7, 2015 Share Posted September 7, 2015 500-1000$ probably. They will just chnage parts instead of cleaning. I havent had a problem since i cleaned it. About 3 yeara ago?? Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
emt1581 Posted September 7, 2015 Share Posted September 7, 2015 give it a few weeks Been a few months....still fine. The airbag light comes and goes which just means I need to work on or replace the overhead light board. Other than that, no issues. -Emt1581 Link to comment Share on other sites More sharing options...
RSdude Posted November 7, 2015 Share Posted November 7, 2015 (edited) I know this is an old thread, but I've searched many forums and haven't found any with a permanent solution. I've been having this problem on my 2005 Baja Turbo 5MT w/ 72K miles since I bought it in May, but hasn't been a problem with my 2004 Baja Turbo 4EAT w/176K miles that I bought in February. The RPMs would fluctuate to 1500 rpms and below at idle or I could feel small surges in gear just before the CEL would come on. I would notice sometimes that the cruise light would flash before the CEL would illuminate. I don't know if this problem is related to the difference in ECUs and people usually don't post about their trans configuration, so I cannot say for sure. This is just my experience. Seems unusual that the car with 176K miles operates fine and the 72K mile car is plauged with this issue. So far, I've done all the tests in the service manual, more than twice. I haven't done any data logging, but I hooked up my Subaru Select Monitor and both signal outputs seem to be normal when I depress the accelerator through it's full range of motion. I've tried swapping the pedals and have even replaced the pedal with a new Subaru OEM part. Nothing has worked. It has started to become a daily occurence and can be quite dangerous in certain situations. I think it has to do with humidity like others have mentioned, because it usually occurs more on cloudy/rainy days and early in the morning/late in the evening. The P2138 code refers to a difference in the voltage output of the two potentiometers in the pedal assembly. I thought that maybe I'd try hooking both signal inputs going to the ECU to one of the signal outputs on the pedal assembly so that there would never be any differences in voltage, causing the ECU to go into limp mode. It has been three days so far and the idle is much smoother, there are no longer any surges, and I have not yet had a CEL. DISCLAIMER !!!! Try this mod at your own risk, but I think that limp mode is much more dangerous and have had many close situations where I've lost the pedal on a busy highway, crossed dangerous intersections or even stalled out on hills. If you try this mod and you have a surge or wide open throttle situation, just be aware that the simplest thing to do is to put the car in neutral before pulling over and turning off the ignition. I say this as a disclaimer, because this situation happened with the Toyota pedal recalls and people died. Below is a link to pictures of the schematic for the pedal position sensor and my jerry rigged wiring job. I unhooked the connectors and used some other terminals I had from another harness to make my mod reversible without cutting any wires. The signal input wires on my car are the blue with white stripe and the white with blue stripe. They are terminals 2 and 5 on the wiring harness. imgur.com/a/io0Fm I hope this helps. Every forum I've read hasn't found a solution and I've even read about individuals selling their car because of this. I'm too stubborn and I love my Bajas. The wife says I have to sell one though. I will report back if I have any further issues. Edited November 7, 2015 by RSdude Link to comment Share on other sites More sharing options...
frank_ster Posted November 12, 2015 Share Posted November 12, 2015 ^ thank you for your input. have you tried cleaning under the cap of the throttle plate ? Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
RSdude Posted November 12, 2015 Share Posted November 12, 2015 I don't know what cap you're referring to, but I have cleaned both connectors on both the pedal assembly and the throttle body assembly with no results. The last thing I tried was cleaning the throttle body and butterfly valve with carb cleaner. Like most turbos without a catch can, there was a film of oil residue that I thought might be causing the throttle plate to stick. If you try this, be prepared for a temporary episode of white smoke coming out the exhaust. Update My modification is still working with no check engine lights or limp mode conditions. I have noticed random micro surges in the throttle like before, but they no longer result in a check engine light and limp mode. The surges are barely noticeable and don't affect the throttle enough to be a problem or a safety concern. Actually, they are so slight, that they do not affect driveability at all. I noticed that I have my modification hooked up to the Sub-accelerator signal, so maybe if I feel like crawling back down into the firewall cave, I'll try the Main-accelerator signal and see if the micro-surges still occur. Link to comment Share on other sites More sharing options...
frank_ster Posted November 15, 2015 Share Posted November 15, 2015 the cover on the throttle body, it has the sensor in side of the cover which reads the magnetic pickup from the throttle plate . i dont think oil can cause issues with this type of sensors. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
tdelker Posted November 15, 2015 Share Posted November 15, 2015 Seems like now that you have iosolated the issue it would be wise to buy a new pedal assembly to have a properly functioning car with correct redundant sensors to make sure you don't have an run away situation. Link to comment Share on other sites More sharing options...
RSdude Posted November 16, 2015 Share Posted November 16, 2015 My throttle body is a sealed unit. The servo and TPS are not serviceable, but this code does not refer to the throttle body, it refers to the a voltage variation in the two redundant sensors in the accelerator pedal. As stated previously, I have replaced the pedal assembly with no positive results. Many other people have tried replacing the pedal too and it has not corrected the issue. Link to comment Share on other sites More sharing options...
frank_ster Posted November 17, 2015 Share Posted November 17, 2015 From my experence this code is for both the throttlebody and the pedal sensor , as i have a buick engine and stand alone ecu along side of the factory ecu. Wheni probed the wires on the theottle body i could recreate the code everytime . The pedal assembly and the throttle body have magnetic contactless position sensors with inverted curves. One ramping up with poaition and one down . If the sensors dont point to the same position the code is set and lompmode acticated. My throttle body when i remove it has a plastic cover where the plug plugs into. I removed that cover and cleaned the metal bits of the magnetic pickup and that solved my issue. If you even force open the servo with your finger with ignition on it will also set this code. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
RSdude Posted November 18, 2015 Share Posted November 18, 2015 This thread is regarding Subaru P2138 code with dual contact potentiometers and factory ECU's. The later models have magnetic Hall effect sensors. To avoid confusing other Subaru owners plagued with this issue, I think your comments regarding a Buick with standalone ECU and magnetic Hall effect sensors belong in another forum. Link to comment Share on other sites More sharing options...
frank_ster Posted November 19, 2015 Share Posted November 19, 2015 This thread is regarding Subaru P2138 code with dual contact potentiometers and factory ECU's. The later models have magnetic Hall effect sensors. To avoid confusing other Subaru owners plagued with this issue, I think your comments regarding a Buick with standalone ECU and magnetic Hall effect sensors belong in another forum. buick engine, all subaru sensors, this thread was started with issues with a 05 legacy gt witch is what i have. i only mentioned the buick engine because i have played with the system and had this even triggered a few times because of my doing and after because of metal chips in the stock subaru throttle body unit. so it seems you have an older version of drive by wire. that i have not seen before. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
emt1581 Posted April 3, 2016 Share Posted April 3, 2016 Been a few months....still fine. The airbag light comes and goes which just means I need to work on or replace the overhead light board. Other than that, no issues. -Emt1581 Been 6 more months...still fine! -Emt1581 Link to comment Share on other sites More sharing options...
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