Unresponsive Gas Pedal 2000 Ls 400

[T-Bone Mike]

My LS 400 has 155000 miles on it but has suddenly had intermittent response to accelerator pedal. This happens at speed. Pulling over and shutting down momentarily seems to remedy but it is a dangerous situation. Any others encounter this and have a fix? Many Thanks - Mike

[steve2006]

I'm not sure if the 2000 year model is "drive by wire" throttle control but if it is I would start with the accelarator pedal position sensor.

[steve2006]

Just looked and it is electronic throttle control so as above check the pedal sensor and wiring and then the throttle position control motor and wiring.

[1990LS400]

My LS 400 has 155000 miles on it but has suddenly had intermittent response to accelerator pedal. This happens at speed. Pulling over and shutting down momentarily seems to remedy but it is a dangerous situation. Any others encounter this and have a fix? Many Thanks - Mike

The problem could be caused by something else (required disclaimer :) ) but my 2000 LS400 had the same symptoms when the TPS (throttle position sensor) began to fail in 2008 and the throttle would work again for a while if I turned off and restarted the engine. I'd have to look up the mileage but I think it failed at about 115,000 miles. Test or have the TPS tested to see if it really is the problem. My PPS (pedal position sensor) was also marginal so I had it replaced when the TPS was replaced.

[T-Bone Mike]

Thanks for your thoughts on this. They make sense to me. - Mike

[T-Bone Mike]

I'm checking a "drill down" parts catalogue and can come up with a Throttle Position Sensor - but no pedal position sensor. There is however a vehicle speed sensor - or is that for the sopeedometer (most likely). Thanks again - Mike

[steve2006]

Yes the speed sensor is for the speedometer and also the transmission.

[1990LS400]

I'm checking a "drill down" parts catalogue and can come up with a Throttle Position Sensor - but no pedal position sensor. There is however a vehicle speed sensor - or is that for the sopeedometer (most likely). Thanks again - Mike

The attached pages from the 2000 LS400 repair manual set show the Throttle Position Sensor, the Pedal Position Sensor and describe how to test them.

sf-36.pdf

[T-Bone Mike]

I just checked back as I'm taking my LS in to my mechanic today. ...PLEASED to find your most kind attachment, Jim. Thanks very much. - Mike

[steve2006]

Please come back when you have an answer to your problem and let us know what it is.

[T-Bone Mike]

Hi Jim - my mechanic wants to change the Throttle Position Sensor and the Throttle control motor as he says he can hear what should be a silent mechanism "grinding". Now, I cna't come up with a throttle control motor through the drill down except for as part of the cruise control. Any thoughts? Thanks, Mike

[1990LS400]

Hi Jim - my mechanic wants to change the Throttle Position Sensor and the Throttle control motor as he says he can hear what should be a silent mechanism "grinding". Now, I cna't come up with a throttle control motor through the drill down except for as part of the cruise control. Any thoughts? Thanks, Mike

Sorry, but I don't know if the throttle control motor should be "silent". Personally I wouldn't change it if it tests within spec but I'm no expert. I don't remember them being nearly as prone to failure as the TPS. Your mechanic "wants" to change the TPS ... but does it test as being below specification?

[T-Bone Mike]

Hi Jim - my mechanic wants to change the Throttle Position Sensor and the Throttle control motor as he says he can hear what should be a silent mechanism "grinding". Now, I cna't come up with a throttle control motor through the drill down except for as part of the cruise control. Any thoughts? Thanks, Mike

Sorry, but I don't know if the throttle control motor should be "silent". Personally I wouldn't change it if it tests within spec but I'm no expert. I don't remember them being nearly as prone to failure as the TPS. Your mechanic "wants" to change the TPS ... but does it test as being below specification?

YES - the TPS tested intermittently bad which was just how it behaved. The car workes fine now - but I don't want to wait for that to happen to me again in 70 mph traffic in the NY metro area. That wasn't as much fun as it sounds! LOL thanks Jim - Mike

[T-Bone Mike]

Hi Jim - my mechanic wants to change the Throttle Position Sensor and the Throttle control motor as he says he can hear what should be a silent mechanism "grinding". Now, I cna't come up with a throttle control motor through the drill down except for as part of the cruise control. Any thoughts? Thanks, Mike

Sorry, but I don't know if the throttle control motor should be "silent". Personally I wouldn't change it if it tests within spec but I'm no expert. I don't remember them being nearly as prone to failure as the TPS. Your mechanic "wants" to change the TPS ... but does it test as being below specification?

YES - the TPS tested intermittently bad which was just how it behaved. The car workes fine now - but I don't want to wait for that to happen to me again in 70 mph traffic in the NY metro area. That wasn't as much fun as it sounds! LOL thanks Jim - Mike

I'm discovering not everyone speaks the same language; I use Lexus of Pembroke Pines for my parts ordering. (I found them through this forum) They couldn't find the "Throttle Control Motor with CLutch" which was on the the pdf you kindly attached. Instead there were two other costly parts - neither with a diagram. Part Number: 8967230010 turned out to have an application in a GS 400 as an idle control and something else in the LS and Part Number: 2206050011 was a throttle lever assembly. I wound up just purchasing the TPS and will forgo having the "grinding mechanism" replaced. OR, as much as I like my motor head experienced mechanic, perhaps he can't follow reading the resistance readings and fixes by the seat of his pants. BUT - When my steering column motors froze up and left the steering wheel tilted up and unable to adjust at all. He took it all apart and cleaned the various motors and mechanisms, reassembled it and it has worked fine for 3 years since.

[1990LS400]

YES - the TPS tested intermittently bad which was just how it behaved. The car workes fine now - but I don't want to wait for that to happen to me again in 70 mph traffic in the NY metro area. That wasn't as much fun as it sounds! LOL thanks Jim - Mike

Yes, it certainly can be an "interesting" experience when a TPS fails ... engine running but the gas pedal does little or nothing. Mine failed on a Spring 2009 evening while I was doing U.S. Census work at the end of a dead end street in a neighborhood I definitely didn't want to be in after dark. Having the required government placards on my car didn't make me feel good either and neither did having a nice shiney new looking car when most of the other cars on the street looked like wrecks or were up on blocks. As I was trying to get my car to move from a standstill, about 10 young tatooed guys holding beer bottles approached my car. They were maybe 20 feet away when my car suddenly lurched forward and I waved to them as I drove away. Maybe nothing bad would have happened but I'm glad I didn't have to find out.

T-Bone Mike, how many miles are on your car?

[T-Bone Mike]

YES - the TPS tested intermittently bad which was just how it behaved. The car workes fine now - but I don't want to wait for that to happen to me again in 70 mph traffic in the NY metro area. That wasn't as much fun as it sounds! LOL thanks Jim - Mike

Yes, it certainly can be an "interesting" experience when a TPS fails ... engine running but the gas pedal does little or nothing. Mine failed on a Spring 2009 evening while I was doing U.S. Census work at the end of a dead end street in a neighborhood I definitely didn't want to be in after dark. Having the required government placards on my car didn't make me feel good either and neither did having a nice shiney new looking car when most of the other cars on the street looked like wrecks or were up on blocks. As I was trying to get my car to move from a standstill, about 10 young tatooed guys holding beer bottles approached my car. They were maybe 20 feet away when my car suddenly lurched forward and I waved to them as I drove away. Maybe nothing bad would have happened but I'm glad I didn't have to find out.

T-Bone Mike, how many miles are on your car?

My car has 155,000 miles on it. I purchased it in 2004 with 50,000 miles as a CPO. I've never regretted it. Thanks again for your help. - Mike

[lextechrob]

Try cleaning the throttle 1st, if that does not do it, just replace the throttle body assembly with a used one. Easy to change and pretty cheap. Common for worn throttle motor gears to trip a fault and take away the throttle.