I remember one point when my vehicle problem: start, the engine runs at around 1000 RPM but not accelerate, if I pull to D or R, it stops.

Is my vehicle error caused by ECU/ECM. Some recommend me to replace ECU/ECM. Anyone has experience with ECU/ECM replacement?
Is this one fits my vehicle, just buy and replace?

 

Like even if you floor it, it did not affect the car's behavior in any way? Did the pedal feel like usual or it just dropped to the ground?
And what do you mean by "it stops" - did the engine just stall or the issue went away?

Your accelerator pedal is directly connected to the throttle body, so the engine should either rev-up or start choking. If it did not affect completely anything, the only thing that I can think of is an accelerator cable (?)..
Next time something like this occurs, try accelerating from under the hood, acting directly on the throttle body and see what happens. Also, pay close attention to the sensors data.
You can also try filming it to give a better understanding of the issue.

Hope this helps and best of luck!

 

It is definitely tempting to suggest that it may be an ECU failure.
The ECU replacement is kind of a process, you may need to re-program it (I actually have no idea if you have an immobilizer, can you send a picture of your key?).

I would suggest leaving it as it is for now, since, as you wrote, the issue went away for now. Wait until it shows itself again, and try scanning the ECU. If your scan tool will not connect and you won't see any Check Engine light in the "ON" position, then I would definitely suggest replacing the ECU.

Hope this helps and best of luck!

 

Do you mean my vehicle key?



Do you know the location of the Vehicle Speed Sensor, I can not see it


My vehicle

 

It seems like your car doesn't have an immobilizer, meaning that it will be much easier to replace the ECU.

Here is a thread about Vehicle Speed Sensor replacement.

But if you are looking for it because of my previous post, I meant a different thing - by "accelerating from under the hood" I mean pulling on the throttle cable (see attached photo). It is a cable that actuates a flap that is inside the throttle body, allowing more air into the engine, thereby increasing its RPM. When you step on the accelerator, you are pulling on a throttle cable, which, in turn, actuates that flap. What I suggested to do is to go under the hood and basically "bypass" the accelerator, acting directly on the throttle body.
You need to replace your VSS only if your speedometer doesn't work, or you have a Check Engine P0500 code.




Hope this helps and best of luck!

 

I currently use a clone key without any circuit inside. It does not have anti-theft.
Thank for your guide about throttle. So I do not need to focus on it in term of mechanic.
But I wonder if the VSS failed or the wiring/connector to it broken.


so it does not send the right information to ECU? In this case, can ECU does something to stop the engine accelerate then cause my vehicle problem?

 

Symptoms of a bad VSS - fluctuating or inaccurate speedometer, rough transmission shifts, Check Engine light with the P0500 code.
If you don't have any of those, your VSS sensor is in good working condition, and you don't have to worry about it.

That is basically what I wanted to know, it means that the ECU doesn't have to store your key information, meaning that you won't have to re-program it after the ECU replacement, which makes this process that much easier.

Yes, you do not need to worry about the throttle body malfunction, just if you would encounter your issue again, try going under the hood and accelerating from there.

Hope this helps and best of luck!

 

Today, after running 5 miles more, the vehicle throws check engine light ON


and it has the error code:



I check throttle via OBD-2: without accelerator pedal press down: 10.2%, increase up when I press pedal. It means that throttle sensor and its wiring still OK?, or we need to check it?
I notice that when I start the engine let it run without pressing accelerator pedal, sometimes the engine increases RPM a little bit then returns down to normal

In the present time, the vehicle still OK and I can drive it normally . I have one question that if 1995 Lexus es300 has Accelerator Pedal Position Sensor? Does ECU compares TPS voltage and Accelerator Pedal Position Sensor Voltage, if these voltages are not matched, ECM throw the error code P0510? I still look for the throttle system operation of this vehicle

 

This code most probably means the TPS, since your car doesn't have any Pedal Position Sensors or Full Throttle Switch.

Sometimes it is normal for the engine to adjust a little bit, especially with your CE code, you just don't want it to be way off (increase from 800 to 2000 RPM or something like that).

For now, you can try disconnecting the sensor and see if anything changes, that can be a good indication. If the sensor is disconnected, an ECU starts to run in a "guess mode", meaning that it goes in trial and error to work out the best setup. Not the best key scenario, but it is still better than a false signal.

Hope this helps and best of luck!

 

I do mistake: OBD-2 show throttle 10.2% open, not 10.2V. Thanks Arsenni. Do you know base on what information, the ECU throws the check engine light ON? ( I mean the operation of ECU on throttle system).
I know that base on the throttle voltage, ECU will control the fuel quantity to engine room: low voltage --> low fuel supply. If I disconnect the throttle sensor, no voltage on throttle wire to ECU, that is the same with throttle open 0% , the same with no pedal pressing --> ECU blocks fuel --> no fuel to engine room --> can not accelerate ?

I really do not understand my circumstance: throttle voltage still OK because OBD-2 tester show throttle % and this changes up and down when I press or release the gas pedal. It means press pedal ==> throttle open --> throttle voltage up --> OBD-2 recognize. So the sensor is OK and ECU receives the good information. But why it throws error code? Does ECU compare the voltage with another voltage? And this another voltage is error --> ECU throws error code?.

If ECU only bases on throttle voltage to control fuel quality,in this case my vehicle throttle voltage is OK, so why and base on what make ECU throws error code? And what cause my vehicle sick?

 

It is so, but here is a catch - the throttle should be closed when the pedal is released. A while ago, the idle was adjusted by a screw on a throttle body, hence why it was always opened, but in newer cars (your engine already has it), the engine idle is done by utilizing an idle port, which is controlled by the Idle Control Valve. What I'm saying is that your sensor is still sending signal to the ECU, regardless if it is correct or not.

I finally ran some tests on my working sensor, and got some base numbers - I measured a resistance between Ground and Signal pins on the sensor (see attached picture), and I've got 0.5k Ohms with the closed throttle, and 2.1k Ohms for the fully opened. I also tested the voltage that goes from the Signal pin - when the throttle is closed, there should be around 1V, and when it is fully opened, there should be close to 5V. Just be careful with the wire, I would suggest getting yourself a wire probe tool, since it can reach to the wire without damaging the isolation too much.



Your logic is completely right, but the catch is that the sensor always sends around 1V back to the ECU to let it know that the sensor is still there and working. If this signal would disappear, the ECU will switch into the "guess mode", meaning that it will start trying to predict what is the throttle's position, based on other sensors. The only problem with this is that it will not be a smooth ride by any means..

Hope this helps and best of luck!

 

Is this the Idle Valve sensor, not TPS?

You mean that I can take out the TPS connector and drive the car?

 

this is my vehicle TPS connector. It has 4 wires, 1 and 4 may ground and 5V, 3 maybe throttle voltage wire and 2 maybe Idle Voltage?

 

I am sorry, I forgot that your car has a pre-VVT-i engine.. My solution will not work out for you.
I think I know what the issue is - your TPS is combined with the Closed throttle switch, which, judging by your code is the issue. So you probably just need to adjust your sensor.
Here is a thread that talks about the older TPS style. Do not follow the links in the first post, go down until you will see "adjusting the TPS Throttle Position Sensor".
Connector that he wrote about is called Molex, and can be obtained at any electronics store. The rest is pretty self-explanatory.

Hope this helps and best of luck!

 

When I intended to replace the TPS, one man said that my vehicle problem due to ECU losing its data, due to battery replacement, then I need to make ECU relearn. Is this true?