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GS400 Throttle Body Problem

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Old 06-25-14, 08:56 AM   #1
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Default GS400 Throttle Body Problem

The other day, my GS4 decided to stop driving forwards. It would go in reverse and the car would rock somewhat violently when I would shift between park and reverse. My CEL was already on due to an exhaust leak but the VSC/VSC OFF lights came on.

I turned off the car and waited for my wife to come pick me up. I figured I would start the car back up and see if it was working again. At that point it drove fine. I had the codes pulled and it indicated the TPS is bad. It supposedly did not have the other code for the accelerator position sensor. Once I was almost home, it happened again and I was able to get the car home by turning it off and restarting it.

It looks like in most cases the TPS is fine and it's either the motor or the APS. I'm hesitant to rely on most of the info in the huge thread about this because it seems to mostly be GS3 related and the thread is cluttered up and confusing with people posting about completely unrelated problems.

I'm looking for experiences from other GS400 owners who have fixed this problem. How exactly did you figure out what component was bad and where did to get the replacement parts from.

Last edited by sivikvtec; 06-25-14 at 09:01 AM.
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Old 06-26-14, 09:46 AM   #2
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Hello Clark, thank you for the message. I believe the best plan of action at this point would be to take a multimeter and check the resistance on each part to help narrow it down.

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Old 06-26-14, 11:47 AM   #3
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Excellent advice...
The multimeter is an important tool, learning how to use it will save time and money.
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Old 06-28-14, 06:24 AM   #4
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Thomas, thank you so much for the help!! This is exactly what I needed

It looks like the clutch is bad on my motor.

Did you replace your motor with the GS300 one (89672-30020)? Did you have any issues? The OP in the thread below said a grommet size was different? What is he talking about, I assume it is this?

Does the entire throttle body need to be removed because it is impossible to gain access to the lower mounting screws for the cover that goes over the TB motor? I guess it was different on the older 1UZ motors and there was enough room to get in there, so I cannot keep the TB installed as shown in the .pdf linked below?

Also, I assume that I will need to bleed the cooling system afterwards because I have to disconnect that small hose in order to remove the TB. To bleed the system, do I just let the car run with the radiator cap off and the heat all of the way up?

Last edited by sivikvtec; 06-28-14 at 09:21 AM.
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