VSC and VSC Off Lights - Limp Mode - Page 27 - ClubLexus - Lexus Forum Discussion


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VSC and VSC Off Lights - Limp Mode

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Old 07-18-13, 05:33 PM   #391
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OK, just spent an hour or so messing with this TB. First off, 2 months ago when I replaced the APPS the TB was clean as a whistle. Today I had to clean it around butterfly about an inch out. Not terrible but more than I expected to see. The ohm ranges are spec'ed out at 68 degrees. It was 95 here. Reading on APPS and TPS were 4.53 exactly for both. This should be expected because higher temperature leads to more resistance. The TCM was making a little bit of a friction noise and the ohms were low even considering the high temp. I think it is the TCM
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Old 07-18-13, 06:36 PM   #392
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little research on resistance and temperature. With the wiring in the car, the ohms will increase linear with temp increase. If that is the case then, 68F/3200ohms = 96/x : X= 4,532 ohms at 96F

Can anyone confirm this?
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Old 07-18-13, 06:38 PM   #393
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Quote:
Originally Posted by burny View Post
OK, just spent an hour or so messing with this TB. First off, 2 months ago when I replaced the APPS the TB was clean as a whistle. Today I had to clean it around butterfly about an inch out. Not terrible but more than I expected to see. The ohm ranges are spec'ed out at 68 degrees. It was 95 here. Reading on APPS and TPS were 4.53 exactly for both. This should be expected because higher temperature leads to more resistance. The TCM was making a little bit of a friction noise and the ohms were low even considering the high temp. I think it is the TCM
I don't think it's the motor unless you're seeing a trouble code. A little grinding/buzzing is normal, at least based on my personal experience with my car.
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Old 07-18-13, 06:44 PM   #394
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little research on resistance and temperature. With the wiring in the car, the ohms will increase linear with temp increase. If that is the case then, 68F/3200ohms = 96/x : X= 4,532 ohms at 96F

Can anyone confirm this?
The best way to test TPS and APPS is to insert a metal pin into VTA1 or VTA2, then measure the output voltage as you rotate the APPS lever. If the APPS isn't working properly, then you will probably not see any change in the TPS.
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Old 07-22-13, 09:12 AM   #395
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little research on resistance and temperature. With the wiring in the car, the ohms will increase linear with temp increase. If that is the case then, 68F/3200ohms = 96/x : X= 4,532 ohms at 96F

Can anyone confirm this?
My APPS and TPS show ~1400-1500 ohms at 82F. Have you checked the calibration of your DMM? I don't have access the the car at this time to recheck resistance at 96F, but I suspect that the value would still be within spec when the engine is warm.

Were you able to fix the limp mode problem after changing out the motor?
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Old 07-22-13, 11:36 AM   #396
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Hi, what is a DMM? The motor came Fedex saturday but I was not home to sign for it. Now they don't deliver until Tuesday. FedEx sucks. Car is in the garage torn down.
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Old 07-22-13, 02:05 PM   #397
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Im pretty interested in your repair of the APPS, did you repair some metal/carbon brushes inside of it, or what?

Nice to have a new spare now huh! :-) just in case.

Also, thanks for the info on voltages etc, my electronic repair manual is "somewhere" on my old computer drive, so I mostly just help people by memory, having exact values on the voltages and signals is nice. Thanks.



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NP! Post back with your results. Toyota designed a flawed APPS. I bought a new APPS, but decided to disassemble my old APPS to see if I can decipher the failure mode. Took me three hours to make the corrective mod. So far so good. I still have a new sealed APPS (P/N 22060-46010) available for sale. Paid $275 with Toyota invoice. Local cash pickup in S Cal only.

I can help members who are local to S Cal trouble-shoot a defective APPS. The APPS will almost always test OK when cold. This part will usually fail when the engine is warm, resulting in erratic or no signal output at the VTA1 and VTA2 terminals. List price at Toyota is $400, but you can buy it online for about $300.

http://www.toyotapart.com/22060-46010.html
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Old 07-22-13, 02:09 PM   #398
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To Everyone:

One bit of advice I would suggest to ALL people working on engines with "newer" electronic controls is to get a Multi-Meter capable of reading Duty Cycle...almost all of the voltage signals going thru these cars, especially to controller motors and solenoids are Pulse-Width-Modulated signals, and reading voltages on them with normal voltage meters can be misleading.

Ive been working on my BMW lately and it saved me all sorts of time in diagnosing whether or not signals were being sent correctly

Just a suggestion.
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Old 07-22-13, 06:47 PM   #399
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Im pretty interested in your repair of the APPS, did you repair some metal/carbon brushes inside of it, or what?

Nice to have a new spare now huh! :-) just in case.

Also, thanks for the info on voltages etc, my electronic repair manual is "somewhere" on my old computer drive, so I mostly just help people by memory, having exact values on the voltages and signals is nice. Thanks.
This particular unit needs a 0.023" to 0.025" shim added between the white Teftlon back plate and the end of the rotating shaft. I use aluminum but shim can also be made out of steel. I glue the shim to the end of the rotating shaft.

The basic design of the APPS consists of two variable resistor pads that act over 90 degrees of rotation to supply VTA1 and VTA2 to the ECU.

The stepping signal at the control motor is also seen at the output side of the APPS (VTA1 and VTA2) in the form of noise spikes if the motor is connected to the ECU. I don't know if this is due to inadequate signal filter from the ECU or sign of a degrading ECU. The VTA1 and VTA2 outputs from the TPS are free from this anomaly.
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Old 07-22-13, 06:48 PM   #400
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Quote:
Originally Posted by burny View Post
Hi, what is a DMM? The motor came Fedex saturday but I was not home to sign for it. Now they don't deliver until Tuesday. FedEx sucks. Car is in the garage torn down.
Digital Multi Meter.
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Old 07-22-13, 06:55 PM   #401
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Quote:
Originally Posted by az-dave View Post
To Everyone:

One bit of advice I would suggest to ALL people working on engines with "newer" electronic controls is to get a Multi-Meter capable of reading Duty Cycle...almost all of the voltage signals going thru these cars, especially to controller motors and solenoids are Pulse-Width-Modulated signals, and reading voltages on them with normal voltage meters can be misleading.

Ive been working on my BMW lately and it saved me all sorts of time in diagnosing whether or not signals were being sent correctly

Just a suggestion.
True. That's why I use an oscilloscope to inspect the waveform. You can attach the input to channel A and output to channel B to check for proper operation. This is one way to isolate an intermittent condition caused by thermal or vibration.
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Old 07-23-13, 01:31 PM   #402
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Another thing I noticed is when I step on the gas it just completely shuts off.
I would check and see if you have the TPS on correctly.
It has to go on and then turned counter clockwise.
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Old 07-23-13, 08:04 PM   #403
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Wow, fun night. Took entire throttle body off car and cleaned it like new. Installed new TCM and TPS. Had to adjust new TPS 3 times to get idling perfect. Car runs as good as it did when it was new. Drove it an hour with no issues. Daughter has it now and will keep me updated. Car threw codes and VSC lights came on upon initial startup. Cleared them and they never came back. Think I am good to go. Thanks for all the input.
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Old 07-24-13, 08:45 AM   #404
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Wow, fun night. Took entire throttle body off car and cleaned it like new. Installed new TCM and TPS. Had to adjust new TPS 3 times to get idling perfect. Car runs as good as it did when it was new. Drove it an hour with no issues. Daughter has it now and will keep me updated. Car threw codes and VSC lights came on upon initial startup. Cleared them and they never came back. Think I am good to go. Thanks for all the input.
Let's hope this gremin is gone for good. The official method of adjusting the TPS is to attach an OBD II reader and turn ON the ignition switch without touching the gas pedal. Do not start the car. Adjust the throttle opening to 14.8% plus/minus 0.8% using the TPS. You can also hook up an accurate multi meter to the VTA1 output of the TPS to obtain a reading of ~0.732 VDC.

The engine will ide high after you clean the throttle body. This is normal as the ECU will learn to dial in the correct idle speed after several drives. I would advise against adjusting the TPS to achieve the desired idle speed when warm.
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Old 07-24-13, 09:48 AM   #405
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Nice work on that! I have solved similar problem with a ring sensor on GM 4WD trucks thats inside a $600+ "Encoder Motor" (the device that changes the Xfer case from 2WD to 4WD 4Lo etc)

GM dealers will only replace the entire encoder motor assembly, no ifs and or buts. But the ring sensor is a $64 part, takes 2 hours to replace.

Its a Hall-effect variable resistor, but the issue with it isnt a shim, its the tiny metal brushes they use wear out, and then scratch the resistor down to substrate. BAD BAD design.

I appreciate your technical info on this issue. I diagnosed this Limp-Mode problem using older fashioned methods and a std DMM before they had Duty Cycles, and I dont have a scope. I did that because Lexus would Only commit to replacing then entire Throttle Body if it wasnt the TPS sensor (which I already knew wasnt due to readings) so thus my journey started.

Quote:
Originally Posted by furballi View Post
This particular unit needs a 0.023" to 0.025" shim added between the white Teftlon back plate and the end of the rotating shaft. I use aluminum but shim can also be made out of steel. I glue the shim to the end of the rotating shaft.

The basic design of the APPS consists of two variable resistor pads that act over 90 degrees of rotation to supply VTA1 and VTA2 to the ECU.

The stepping signal at the control motor is also seen at the output side of the APPS (VTA1 and VTA2) in the form of noise spikes if the motor is connected to the ECU. I don't know if this is due to inadequate signal filter from the ECU or sign of a degrading ECU. The VTA1 and VTA2 outputs from the TPS are free from this anomaly.
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