20 Most Recent 1998 Lexus Gs 300 Questions & Answers

I wanted to start a thread specifically about failures within the throttle body concerning the GS300 (1998 in my case)

My symptons were:
VSC, VSC OFF, and ENGINE Lights would come on, followed by my car going into Limp Mode, where only that last 25% (if that) of the throttle would respond (basically have to floor the pedal to even move at all).

During the mornings, or when the engine was COLD, the throttle operated normal...then once the car warmed up, usually at about 10 mins, the problem would start...it happened intermitantly at first...1 or 2 days over the course of a week, then it became more consitent, until last week it became a daily problem.

The first part I tried was the Throttle Position sensor, which is on the front side of the throttle body, and the easiest thing to replace...this didnt help at all. $300 part from Lexus, $80 part from RockAuto.com (exacly same part toyota OEM)

"Idle Valve Motor", which is the larger electrical object next to the TPS on my 98 GS300. Problem is solved.

The Codes I got were P1120 and P1121 - Accelerator Sensor problem. However it wasnt really the Accelerator Sensor, it was indeed to actual electrical Motor that controls the opening of the Butterfly valve inside the Throttle body.

I found the problem by good old trouble shooting, and using an ohm meter to see if the throttle electric motor was getting elev, I found that the elec motor just to the left of the TPS was basically freaking out and shutting down. The Accelerator Pedal Sensor is on the Back-side of the throttle body where the throttle cable connects to, and has a spring on it. It was fine.

GS300's are indeed "drive by wire" concerning the throttle...the cable triggers the Accel Pedal Sensor, which sends a signal to the ECU, the ECU then sends power to the Idel Valve Elec Motor (next to the TPS), which opens and closes the mechanical butterfly valve, then the TPS sensor detects how far the elec motor is actually opening the butterfly valve...its a closed-loop feed-back system, meaning any failure in any sensor will cause the entire systm to fail.

The throttle cable apparently is ONLY there to allow the fail-safe of having that last 10-25% throttle when the electronic system fails...there is a gearbox inside the throtle body which allows the tail end of the throttle to manually engage the butterfly valve...the rest of the time, the butterfly valve is 100% opened and closed via the idle control motor.

1998 Lexus Gs... | Answered on Aug 21, 2020

amigo revisa los terminales de los cables de bateria que tengan buen contacto, en segundo lugar revisa que el alternador envie el voltaje apropiado , avisame [email protected]

1998 Lexus Gs... | Answered on Jan 23, 2018

its the brake system has a problem,,ether the accumulator or the sensor of four tires,,check in diagnostic tools

1998 Lexus Gs... | Answered on Sep 28, 2017

Its on the passenger side wall by your right foot open the door get on your knees and look up on the wall right under the glove compartment.

1998 Lexus Gs... | Answered on Jul 29, 2016

In my case, there was a quarter stuck in the track. The seat had to be removed. If it is an electronic seat, I suggest checking the fuses.

Additional information would be helpful.

1998 Lexus Gs... | Answered on Mar 21, 2016

Try moving the steering wheel a little bit in each direction. If the column is locked it may prevent the key from turning.

1998 Lexus Gs... | Answered on Mar 12, 2015

Mice living in the air cleaner perhaps? It isn't as daft as it sounds as a car laying undisturbed for a while offers mice a very good home and they love to chew pipes and wiring.

The idle air control could be sticking and damp could have got into the oxygen sensors, or anywhere else...
Good luck!

1998 Lexus Gs... | Answered on Feb 21, 2015

Hi follow this link , i know it refers to a different model lexus but i'm pretty sure the procedure would be the same, otherwise ring a Lexus dealer and ask them for the procedure but knowing these top marque vehicles they do like to charge for doing very little , hopefully this link will help
How to Reset the Anti Theft Lock on Lexus LS400 Sedan eHow

1998 Lexus Gs... | Answered on Sep 30, 2014

Well code 125 means the engine is not getting hot enough for the emission system to go into closed loop. So you would check the thermostat first. If the engine is reaching normal operating temp of 195 degrees there could be a problem with one of the O2 sensors or the coolant temp sensor.

1998 Lexus Gs... | Answered on Aug 06, 2014

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