Good Afternoon. Have a 2001 GS300 that is throwing a P0120 code but also upon initial crank, while it immediately fires up, the engine quickly dies - within a few seconds. The TPS was replaced by someone else (it does look new) and after the previous owner replaced the TPS, it still throws a P0120 code, but I am not sure if that is the cause of the engine shutting down within in seconds of starting. It seems like while the engine gets enough fuel to start, it quickly becomes starved of fuel and dies out. When the engine runs for a few seconds, it sounds quite smooth, it doesn't run rough, I can even accelerate the engine RPMs for a brief moment before it dies out. I turn the key off, turn it back on to let the fuel pump charge up, then crank the engine and it fires right up, then dies shortly thereafter. Perhaps a bad fuel pump and/or clogged filter? Is the filter in the tank with the fuel pump or located elsewhere? Or, is indeed the P0120 the cause of such behavior? Any ideas on where the problem could be? Trying to help a single mom with a teenager get back on the road.

Thx,

Paul

 

A few suggestions from me would be to check the tension on the throttle cable and check for vacuum leaks after the MAF. If you have a big enough leak the ECU will almost completely lean the system out and stall without much sputtering or noise. Not sure that the P0120 code would make the car stall. Keep in mind that because the GS300's throttle body is a hybrid system (mechanical and electronic) you could still operate the engine up till about 40% throttle, as its right around that percentage of throttle and above that the TPS is used. Just to clarify, you did clear the P0120 code and it came up again?

 

Thank you much for the suggestions on the vacuum leak, I will check and see if that exists. Yes, I did reset the code and it came right back.

 

Doesn't sound like a fuel pump. Sounds like a fault in the TPS or ETCS. Once the car recognizes it's running, it will manage the idle. Sounds like that's not happening - starting fine but then dying pretty quickly... due to what - I'd start with the code you're getting. The car's ECU manages the idle (and 90% of all throttle input) via this electronic mechanical (ETCS) based on what the TPS is measuring & reporting. Cable is irrelevant to idle and everything except the last 10% of throttle input (90-100%). You're going to need some diagnostics to determine what's going on. Given it was the last variable adjusted, I'd suspect the TPS is faulty or dead. Try unplugging it and see if the behavior changes at all - if it doesn't, it's a sign you're on to something.

 

Ok, thank you for the advice and great suggestion on unplugging TPS to see if there is any difference in behavior. Will relook at the TPS and see if I can detect any fault and then go from there.

Best,

Paul

 

Hi Kyle and all, I disconnected the original TPS as suggested and started the vehicle and it wouldn't stay running - essentially same behavior was exhibited as previously described. I moved it slightly to left and right while attempting to start the vehicle and again no change in behavior. I removed TPS and replaced it with a new one. The car at least stays running but it runs very rough at idle. Also, there is no throttle response throughout the entire range. Here is a link to very short videos (apologize for the poor quality of them) of engine running and lack of throttle response, running rough, etc.
Reply
- New TPS installed.
- no TPS connected, sluggish throttle, running rough
- TPS installed, connected, sluggish throttle and engine races high rpm and then stays at high RPM around 5500

I attached a couple of pics at bottom of diag codes P0120 and P1121

Not really sure where to go from here. Thoughts?

 

Couple things -

1 - Remember, the cable will only be effective for the last 10% of the pull, so a non-response from the TB when you move the cable earlier in the pull is not surprising.
2 - I'm not sure on the history of this car, but if it's running rough, there could be other issues beyond the idle / TPS. Timing and basically any vast number of other issues could be at play causing roughness in the engine
3 - Full disclosure - I have a GTE, not a GE engine anymore in my GS, and I've never had to set the TPS - however, do a little searching and you can probably find some tutorials on it - here's one I dug up: https://www.clublexus.com/forums/gs-...libration.html
4 - It's possible other components of your throttle system are faulty - including the APS (I think) - Pedal position sensor - this talks to the ECU, along with the TPS to establish the correct actual operation of the throttle plate (ETCS). ETCS motor is also part of the equation. I'm not insinuating any of these components are also faulty, just reminding you they're all part of the same system that collectively are at play.

 

I'm having a similar issue with my 01 GS300, I was driving in on a really hot day and I was sitting at a stop sign, as soon as I pulled off it felt like some sort of hesitation but drove fine for a few miles until my car went into limp mode and I was only able to use the last 10-15% of the throttle to drive around, I took it to a local shop and it gave p1120/p1121 so they replaced the throttle body with one off a is300 as well as a new apps and a new tps, the shop tested everything with an ohm meter and everything was in spec but it was still throwing code p1120 so I ended up driving it around for a couple weeks until I replaced the throttle body motor which when I did that the car got stuck at 3k rpm and when I turned it off and tried to turn it back on it would rev up to 1200 rpm and shut off like it lost fuel, I've checked for vacuum leaks and faulty wiring but the only thing ive found was a litte bit of oil in one of the ecm connectors. could it be an ecm issue? just wanted to get some opinions before I keep throwing more money at this thing.