Apologies in advance for making a new thread, but I've ran into an issue that I can't seem to find info on in the service manual. This past weekend I had planned to swap my engine due to a coolant leak that I thought was originating at the head gasket. Once I had everything disassembled I noticed that it was actually coming from the water neck and turned out to be due to a disintegrated thermostat o-ring. I was running out of time anyway, so I decided to patch the leak with a new o-ring and reassemble instead of proceeding with the engine swap. During a test drive I noticed that the transmission no longer kicks down at all when mashing the throttle at any speed. It launches from a stop just fine and is confirmed to be getting full throttle, so I'm pretty sure it's not the throttle cable. It also shifts smoothly and predictably. I labeled all of the connectors while tearing it all down and am pretty sure that everything was reattached correctly. This leads me to believe that the issue may be with the throttle position sensor. I also unfortunately can't check for codes at the moment because my crappy OBDII Bluetooth adapter decided to start crashing my phone. The only other factor that I think is worth mentioning is that I also changed the transmission fluid using Toyota type IV. This has me a little worried because the only troubleshooting recommendations I could find in the service manual point to a problem with the valve body. Thoughts? Any help would be tremendously appreciated.

 

@MPRZ Hi, My car Scion xB 2004, had like 2-3 years ago a head gasket defect symptom. I was to 2-3 mechanics for a diagnostic. No one was sure. Then I find a "wizard" mechanic with great wisdom.
He start tell me things that I can not confirm or deny that can be the reason of mall functioning. He assure me that is not the engine problem. There is a symptom, there is a diagnostic, and a(re) solution (s).
My car was neglected in the past 10 years.So, we start the so called "decade" maintenance. He becomes my car "fitness personal trainer".
Was replace:

1. All radiator hoses with new silicon of high quality.
2. Front radiator + fan assemble.
3. Interior heater core.
4. Thermostat and water pump.
5. 2 belts of the engine.
6. New High output Amps Alternator (200A).
7.New transmission filter (x3 times in one Month).
8. New 100% synthetic engine oil (AMS oil).
9. Flush the interior engine with Kerosene (big time to clean all the sludge).
10. Was replaced majority of the sensors.
11. Was open and clean the idle throttle.
12. The intake was clean from the opening near front driver side to the engine.
13. We got a brand name, brand new battery Deka, "imported" from Pennsylvania.
14. Replace all 4 tire, do balance and front Allingment.
15. Check the calipers for usual damages.
16. Replace the PVC valve so will not have an oil consumption.
17. Check all the electric system power consumption (here we replace some lights front/back to LEDs.).If the computer get a voltage with too much fluctuation
(if the steady state is not reasonable), the computer will do mistake at the spark plugs and transmission mall function.
18. Check if the engine motor mounts are in place and the engine is aligned with the transmission. Must be at 0 degrees.
19. Check the exhaust from the engine to the end (muffler). If there is an obstruction need to be fix.

This car mechanic teach me a lot (for free). Not really! I had to pay for repairs (about $2,000/year).
I hope that my old list will give you something to think about.
Please let me know when is the point (nostalgic), to say Good bye to you old car?

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Thank you.

 

How did you go about changing the transmission fluid?

 

@MileHightC Hi, If you ask me the question about the transmission fluid I can tell you the full story. Please let me know if you like to know?
Thank you.

 

Just a drain and fill. My plan was to swap the engine and trans, but I had limited time and ran into a few snags so everything ended up staying in place for now. The fluid was last changed about three months ago with a new filter and everything was fine. I didn't drop the pan at all this time.

 

Is it at the proper level when at operating temp while on and in park? Seen this type of behavior when it's low with ATX.

 

Yeah, the fluid is at the right level. I always check it running when hot and on a level surface. It goes into gear and shifts very smoothly otherwise.

 

That's good. Always nice to be able to rule that out and you can never ask too simple of a question on the forums lol.

 

Alright, so I did a little more troubleshooting and am at a complete loss. The ECU is throwing no codes whatsoever. I did have the battery disconnected for about a week so the codes should have been cleared, but I figure that any problems with the valve body solenoids or various sensors would show up right away. The overdrive switch functions normally. The only other odd behavior I noticed is that at full throttle from a stop the shift from first to second occurs at around 4,500 RPM. This leads me to suspect that the TPS may be at fault. I'll have no way to know for certain without replacing it, but I really don't want to spend $75 just to find out the problem is with something else. Could this be caused by a vacuum leak? Also, can anyone here explain to me exactly how the kickdown function is controlled on this car? Google so far has been of no help in pointing me in the right direction.

 

@MPRZ, according to my car mechanic, the VVT valve is in charge with "feeling" the engine needs of delivering more power. That VVT valve let extra oil to navigate faster in the engine as needed. It is acting like an "observer" and "controller".
Some times there is old bad oil stuck in the area of that filter/mesh, and need to be removed manually. That is an easy work with just 10mm socket ranch (first push out the Alternator like 1- -3 inches, then access the bolt). The old School mechanics clean that part with Kerosene.

The Transmission fluid have a stick. If is cold, must check the level of that liquid on his lower marking. If is hot must be at the top marking. That liquid is expanding with the temperature. Must have the red color
(not brown color or any dark color), and must smell like oil (after 100K Miles must be changed as needed and the transmission filter). By doing maintenance, is how majority of the Scion owners will drive theirs car to 0.5 Million Miles!

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Did ya figure it out? this is pretty much all the info if you wanted to test your sensor before buying a new one.

 

Hey, sorry for the late reply (I've been stupidly busy), and thanks for that service bulletin. I'm gonna give testing the TPS as outlined a quick go this weekend, and if it doesn't turn up any problems I'll probably just call it quits with the auto trans. I have a used five speed and almost all the necessary parts ready for the swap. If I can find a master cylinder reservoir this week I'll commence with it next weekend and hope for the best.

 

@MPRZ Hi, I have a Scion xB 2004. The automatic transmission first needs to have the up-grated program software. Then if is NOT performing you can jump to other options.
For your transmission malfunction / torque converter. It is possible (to ask a "honest" Toyota dealer) to do a software re-programming transmission shift?

I like to ask also for general knowledge, does Toyota dealer do re-programming for free? If, not free how much cost?

Thank you.



For transmission re-programming must be a file like this one available.....? Or not?

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Is there a cable from the throttle to the gearbox??
Did it get knocked off somehow??

 

There's no cable, all electronic. No worries though - I'm waiting on just one more part so I can proceed with my planned 5-speed swap after which the automatic will either go on craigslist or straight into the trash.

 

Oh, man. I just realized I never posted an update to this. It turned out to be the TPS all along and was only reading 42% at wide open throttle.
Thanks to mrrcom and RichBinAZ for your advice.

I realize it's been months since I posted, but I wanted to close out the thread in case someone else runs into this same issue.

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awesome job on this repair! Thanks for posting solution!

 

What's funny is that I happened upon it entirely by chance. I had to take the box in for its regular emissions test and decided to scan for codes on the way to the facility to confirm there weren't any. That's when I learned that the Torque app has little widgets for each of the sensors, and the TPS one shows the percentage value. Bingo! I guess my lesson is that trouble codes (or lack thereof) apparently don't always paint the entire picture.

 

yes, OBD is pretty limited for troubleshooting and diagnostics. They'll only throw code if sensors are completely dead or wildly out of range. Thus scanners that read ODB are even more blind.

You suspected TPS earlier, which was very intuitive! Then using tools mechanics have been using for over 100-yrs would have found problem right away. Such as following test-procedure in manual by testing TPS voltage at closed and fully-open positions. Will find that output is still within allowable range (thus no MIL or codes), but out of calibration.

Good job!