Tuan:

If you swapped out the entire TB, then that means you already put in a different TPS sensor, as well as the "fly by wire" - which is the Accelerator Pedal Sensor, also called the Lever Assembly - because they are part of the TB assembly, as is the throttle control motor (sometimes called the idle control motor). In other words...you already did what the mechanic is suggesting.

Unfortunately it looks like youve got some mixed problems, and will be interesting to see what the problem ends up being.

By the way: The term "Fly By Wire" is semi-true in the GS 98-2005 case...there is a moving cable from the pedal to the TB, which turns the Accel Pedal sensor.

The fact you swapped out the entire Throttle Body and same problem would tell me its not the TPS sensor or the Accellerator Pedal Sensor, it would lead me to believe its an ECU issue.

If you swap out everything and it still happens, then Id have to assume one of the new swapped pieces is no good. There are only so many systems and ECU's, and the rest is a mechanical engine,...

 

Just to clarify, 98-00 is cable, 01-05 is drive-by-wire(electronic, no cable) thats actually the techinical term. I didnt make that up.

 

SO that means the accel pedal sensor is inside the car, attached to the pedal...and the TPS sensor is on the TB...a different setup than mine being a 98 with throttle cable.

So...now I have to ask did Taun replace the pedal sensor or just the throttle body?

 

This is all giving me a headach. when I swapped out my entire throttle body, it includes all the sensors and motor. I asked the mechanic again, he said the gas pedal and throttle position sensor would have to be change... I'm going to have him do it as a fool proof plan. If it doesn't fix the problem then I don't have to pay. I been busy lately and don't have time to take it to him yet. Will update.

 

The TPS is relatively cheap, so even though the new TB came with one, if the mech wants to do it as a fool-proof, then may as well.

What year is your GS?

If replacing the accell sensor and TPS dont work, after doing an entire TB, then it must be ECU -OR- a possible short in the wiring between the TB, the ABS/VSC/ECU system.

If its a wire, it could explain why all the replaced parts have resulted in nothing being fixed.

 

I'm having this issue for the past week. CEL, VSC lights, and limp mode. Pulled codes at Pep Boys since Autozone and Kragen/O'Reilly won't do it anymore. Got codes P1120 and P1121.
Did a test with the multimeter and the Throttle motor control was off.
Changed it yesterday and reset the ecu. Drove fine for about 10 miles or so then the CEL, VSC lights, and limp mode started again. Will try and do a multimeter test again and see if the TPS or Accelerator Pedal Sensor (Lever Assembly) is the culprit. If it's the Accelerator Pedal Sensor then I'll just buy a used throttle body. I have to do my timing belt/water pump change and was gonna do my spark plugs as well so might as well remove the throttle body and replace it if that's the case.
I'll update once I find out what is causing my issues.

 

You can test the TPS and the APPS with a multimeter (DMM). Set it to volts, hook it up to the sensor's signal wire, which wire it maybe. Go inside Key on engine off (KOEO), slowly depress the gas pedal all the way down slowly. Monitor the DMM if you see a voltage drop during the depress of the gas pedal. If you see a drop, that's the sensor that needs to be changed. The Potentiometer inside is no good. This method can be used on both of those sensors. Hope that helps.

 

Hey out there I have a similar problem with my 01is300 except I've replaced all the components tps, mass air flow sensor throttle motor still no power....any help??

 

Well according to the thread it can either be your ecu or according to a Lexus tech it could be the shaft inside the throttle body. A Lexus tech here in Cali said they've had issues with the shaft. Of course that could just be them wanting to give me the shaft and charge me $1500 for a new throttle body.

 

So tested the APS and TPS as indicated in the tech manual. Actually tested it near the correct temps and the OHM readings were within spec. I didn't do the drop voltage test indicated by GS4_Fiend since I don't have someone that can depress the pedal for me.
Oh my car is a 99 GS300 btw.

 

Testing resistance doesn't justify the integrity of the sensor. If you got no current flow, you will not see voltage drop. It can pass the resistance test by factory procedure, but that doesn't not mean the potentiometer inside is good. That's why i recommended you my method.

 

You can test the voltage on a 99 by rotating the lever assembly under the hood, because the accel pedal inside the car simply moves the throttle cable.

I think its just on '06 and newer models that dont have the cable. 98 thru '05 all use the same TB, which appears to use a cable and the accel pedal sensor (lever assembly) is on the TB.

 

You can do that on a tps but not on the apps.

 

My GF's car that is giving me problem is also a 99 GS300

I think it has something to do with the gas pedal as well...


I went to electric rebuilder, they rebuild electric component and reprogram ecu in orange county and he told me this guy had the same problem. He changed everything, nothing works so he bought a used ecu and electric rebuilder reprogrammed the ecu for his gs. It still didn't work. Electric rebuilder didn't want to pinpoint my problems because it is too time consuming and they told me they want to change the ecu, throttle body, and gas pedal. Not the pedal sensor, the actual gas pedal. He wanted to charge me 900 for everything which is cheap. Then electric rebuilder recommended me to another guy "TOM'S auto repair" because he's been doing it longer than them and fixed a couple of gs with the same problem.

(Gs4_fiend, that was when I took it to the mechanic and he said I needed to change my tps and gas pedal)

He was kind of a bad ***. I told him that electric rebuilder recommended me to him and that he may give me an alternate route. He called them a "bunch of dumbasses"

Bobadrift you should check him out. He doesn't seem like he'll try to milk you for all your money. I'm going to take my car there next week. I've been busy with work and going air ride on my GS

If you want maybe we can go there together on Wednesday and maybe he'll give us a group fix discount haha.

 

Ok, here is the thing...the gas pedal in a '99 has no sensor on it, it pulls a cable which turns the lever assembly on the TB.

If that cable is moving, which is pretty easy to test, then replacing the actual gas pedal is doing nothing.

GS4_Fend said the '00-05's are completely drive by wire...but im not sure this is accurate, I think its the 06+ - my TB is off an '02, and it has the lever assembly where the cable attaches to, and here are two Ebay auctions showing TB's for '98 thru '05, and they lok identical to mine - the cable attachment is clearly there.:

http://www.ebay.com/itm/98-05-Lexus-...sories&vxp=mtr

http://www.ebay.com/itm/LEXUS-IS300-...sories&vxp=mtr

There is no sensor on the gas pedal if the TB has the Lever assembly.