2005 Turbo Baja (automatic) keeps throwing a P0638 code

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DoubleD
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2005 Turbo Baja (automatic) keeps throwing a P0638 code

Post by DoubleD »

My 2005 Turbo Baja (automatic) keeps throwing a P0638 code

"Throttle Actuator Control Range/Performance Bank 1"

This happens every few months or so. It typically happens if I get a bit aggressive with the gas pedal but it does also happen if I'm just at a stead pace.

The check engine light pops on, the light on the cruise control button starts to flash and the car goes into limp mode and aggressively starts to down shift.

I bought a wifi code reader and app on my phone and I used to be able to reset the code but now it won't reset until I pop the hood and tap on/near what I believe to be the electronic throttle. Then I can reset the code. - I'm not sure if its just a timing thing, that is it takes a while to pop the hod get the screwdriver and tape he back of the throttle thing.

This is getting annoying and could be dangerous - I have read that it could be a dirty intake or maf of ???? Do I use MAF sensor cleaner or carb cleaner spray?

Any suggestion on how to fix this or if its possible to change this throttle actuator with out needing a dealer to activate it.
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kamesama980
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Re: 2005 Turbo Baja (automatic) keeps throwing a P0638 code

Post by kamesama980 »

P0638 means the E-throttle isn't working properly. When any problem is detected, to reduce the changes of something going wrong at more than minimal throttle, the ECM goes into failsafe mode and cuts power to the E-throttle and it reverts, under spring pressure, to about 5% open (1500rpm?) and the ECM controls power in limp-mode via fuel mixture, ignition timing, and cam timing.

Yes you can certainly try cleaning it (the throttle, not the MAF). If you have a spare car and are mechanically and electrically inclined you could even try disassembling it to clean/lube it but keep in mind it's a "no serviceable parts inside" kind of thing as far as Subaru's concerned, the FSM doesn't even consider taking it apart.

I can send the FSM troubleshooting section for that code but it's basically check for power and resistance on each wire under various conditions and if all the wiring's good, replace the throttle body. No mention of needing to recalibrate it.
-Russell
"You don't get to judge me for how I fix what you break"
03 sport 5mt
05 turbo 5mt vf39 and other STI bits, 3" turbo-back
DoubleD
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Re: 2005 Turbo Baja (automatic) keeps throwing a P0638 code

Post by DoubleD »

I guess I've been lucky - it always clears. Recently I have to tap the side of fly by wire module

If u could send the diag procedures I'd appreciate it
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Guacamole
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Re: 2005 Turbo Baja (automatic) keeps throwing a P0638 code

Post by Guacamole »

Here's the 05 FSM for Engine Diagnostics. The p0638 code procedure is on pages 403-410.
http://jdmfsm.info/Auto/Japan/Subaru/Ba ... %20DTC.pdf
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kamesama980
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Re: 2005 Turbo Baja (automatic) keeps throwing a P0638 code

Post by kamesama980 »

Guacamole wrote: Fri Aug 24, 2018 11:27 am Here's the 05 FSM for Engine Diagnostics. The p0638 code procedure is on pages 403-410.
http://jdmfsm.info/Auto/Japan/Subaru/Ba ... %20DTC.pdf
Not sure on the official stance here but publicly posting copyrighted material is usually frowned on by boards. ToyotaNation almost got shut down for it way back 15+ years ago right before I joined but they're also a 50k post/day board last I checked so a lot more publicity... Toyota dealers and corp both have a presence there.
DoubleD wrote: Fri Aug 24, 2018 7:32 am I guess I've been lucky - it always clears. Recently I have to tap the side of fly by wire module

If u could send the diag procedures I'd appreciate it
I'd say that's pretty indicative that you need a new throttle housing (or like I said, try to disassemble and service)
-Russell
"You don't get to judge me for how I fix what you break"
03 sport 5mt
05 turbo 5mt vf39 and other STI bits, 3" turbo-back
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