Legacy_06 Posted May 23, 2010 Share Posted May 23, 2010 Hello all, I have 2006 Subaru Legacy Spec-b. In march of this year my wife and I were driving when our car when it faulted with a check engine/flashing cruise control light, and most noticeably; the car wouldn't rev more than 2000 RPMs (limiting our max speed to 10 mph). My car has been in and out of the Subaru Dealership for the past 2 months. Every time my car has gone in, a stored code of P0638 was present. The dealership has checked all the wire connections of my Electronic Throttle Control System, replaced my accelerator assembly, and replaced my throttle relay. I picked up my car (for the 7th time) on May 20th (2 days ago), and today my car faulted AGAIN!!!!! Both the Subaru dealer and Subaru of America have told me they've done all they can do for my car, and they are unable to diagnose it because the car behaves itself when they have it. Basically they told me not to bring it back. It is my understanding this problem is related to a mismatch in positions between the accelerator position and the throttle position. Has anybody had this same error? If so, please help me out with some direction. I've already paid too much money to have a broken car, and cannot afford much more. Thank you, Mike Link to comment Share on other sites More sharing options...
rao Posted May 23, 2010 Share Posted May 23, 2010 Your dealer sounds like a real winner. The service manual calls for that code to be diagnosed using the info for code P2101. See attached and good luck.P2101 - Part 1.pdfP2010 - Part 2.pdf Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
jagcars26 Posted May 23, 2010 Share Posted May 23, 2010 Your dealer sounds like a real winner. The service manual calls for that code to be diagnosed using the info for code P2101. See attached and good luck. This /\ Link to comment Share on other sites More sharing options...
ehsnils Posted May 23, 2010 Share Posted May 23, 2010 More info here: http://forums.nasioc.com/forums/showthread.php?t=1011316 So did they replace the accelerator pedal assembly and not the throttle body? If they did that then they are probably not too smart. Link to comment Share on other sites More sharing options...
Legacy_06 Posted May 23, 2010 Author Share Posted May 23, 2010 Yes, they only replaced the accelorator assembly and bit the throttle body. Rao: do I need to get a reader to look up the p2101 code? Link to comment Share on other sites More sharing options...
ehsnils Posted May 23, 2010 Share Posted May 23, 2010 ^ ? "bit the throttle body" - What? Didn't they do anything about it? The P0638 code indicates a throttle body malfunction (including opening angle sensor), so if they changed the accelerator assembly they were probably fiddling at the wrong end. Link to comment Share on other sites More sharing options...
Legacy_06 Posted May 24, 2010 Author Share Posted May 24, 2010 Sorry about the "bit throttle," I meant "not throttle." The dealer stopped working on my car because I refused to pay for parts that didn't resolve my problem. Once the accelerator assembly was replaced and my car failed, I got ahold of Subaru of America to get my money back on the parts which were replaced. Once this happened, the dealership would only test drive my car to diagnose it. After looking through the Diagnostic Procedure posted by jagcars26 (Thank You!), I was told all of these steps were taken by the dealer. My thought is they didn't go further to the throttle body and basically gave up. I'm thinking of purchasing a new throttle body. Is the Electronic Throttle Control part of it, or are there two separate parts? Also, as a side note. Subaru of America told me to go to tech.subaru.com to find drawings and manuals. Is this where jagcars26 got the two PDFs? I haven't purchased a subscription yet, but I am looking for technical manuals for my throttle control system. Thanks again for all your help, Mike Link to comment Share on other sites More sharing options...
ehsnils Posted May 24, 2010 Share Posted May 24, 2010 It's all about semantics - the accelerator assembly contains as far as I know (if I'm right - semantics and designations varies) the accelerator pedal which contains an angle sensor that sends data to the ECU which sends data to the throttle body which contains a motor and a feedback sensor. The feedback is then sent to the ECU and if there is a mismatch between the sent data and the feedback data the ECU will consider the throttle body faulty. During winter time the throttle body can suffer from icing and hardened lubrication (as you can see in the NASIOC posts.) This can also cause problems - and someone noted that it may burn the control electronics for the throttle (if that's part of the ECU or if it's integrated in the throttle body is beyond me). So if you have all papers in order that specifies what was changed you should check part designation and part numbers to verify what was replaced. If they haven't documented it correctly then it's probably time for taking it to a higher level with more pressure - legal pressure. Depending on where you live you have different options. To me it still does sound like they replaced the wrong part. Like replacing the steering wheel when there is a puncture... Link to comment Share on other sites More sharing options...
leggtnut Posted December 15, 2010 Share Posted December 15, 2010 This just started happening to my 06 LGT. did it just before thanksgiving and just happened again today. Took it in on black friday and they looked it over and did not find any faults except for the stored P0638 code in the history. verbadum from the service log: "Tech found a code P0638 present for throttle control circuit range performance problem. Tech found current throttle voltage normal at this time, tech suspects outside electrical influence. tech cleared codes and road testsd. All operations normal at this time." Called them again today and they said to bring it in at earliest convience. Ben (2014 Outback SAP w/ eyesite, 2014 Tribeca Limited, 2006 LGT limited sedan) Subaru Ambassador PNW Link to comment Share on other sites More sharing options...
ehsnils Posted December 15, 2010 Share Posted December 15, 2010 No strong radio transmitter nearby? CB/HAM Radio? Or a neighbor doing 1kW CW? A high voltage power line with bad insulators is also a great radio interference transmitter that can make things weird. But in above cases you would have experienced the problem at the same geographical location. Another reason can be a bad battery or alternator. Link to comment Share on other sites More sharing options...
Legacy_06 Posted December 15, 2010 Author Share Posted December 15, 2010 @Leggtnut This was one of the most frustrating experiences I have ever had with any vehicle. I'll give you the outcome, which was found and repaired by myself. The 06 legacy doesn't have physical cable connecting the accelerator to the throttle body. This car is drive by wire, meaning there is a sensor on the accelerator pedal which reads how far to open the throttle body, an actuator in the throttle body (which moves the throttle), and a throttle positioning sensor which tells the Electrical Control Unit (ECU) the position of the throttle. If any of these components are not in the correct position for a certain duration of time (milliseconds), the car will go into a limp mode using the tachometer as the throttle limiting device. My solution after 5 1/2 months, dealing with 2 different dealerships, and Subaru of America was to replace the throttle positioning sensor on my own. The only catch is the throttle positioning sensor is part of the entire throttle body. I found a used throttle body from WOW Auto Parts (online). The cost was $348. Subaru wasn't able to troubleshoot my car because they weren't familiar with this type of technology. I found my solution from an Audi forum. I guess they've been doing this for a while. So far I have over 3000 miles on my car without a glitch. hope this helps. Link to comment Share on other sites More sharing options...
leggtnut Posted December 15, 2010 Share Posted December 15, 2010 Thanks for the info. I will give this to my dealier. Luckly I am still under warranty so no cost to me for this. Ben (2014 Outback SAP w/ eyesite, 2014 Tribeca Limited, 2006 LGT limited sedan) Subaru Ambassador PNW Link to comment Share on other sites More sharing options...
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