sjpitts

I have new to me 2001 Lexus GS 300 that has been going into limp mode with codes P1120 and P1121 and the VSC lights on.

I found this thread:

https://www.clublexus.com/forums/per...limp-mode.html

that describes my symptoms exactly. So I decided to give it a shot and bought a new control motor (OEM Part Number:89672-30020). I am getting ready to replace the motor and I am starting to get nervous. I don't have the factory service manual, and I haven't found anyone that describes the process in depth. I found this video that shows the replacement:


In this video, he shows replacement, and it looks pretty easy. But he doesn't really describe the process in great detail. For example, he shows marking the throttle position sensor but he does not describe why. And he shows some sort of calibration routine at the end, but again does not really describe it.

So does anyone know of a good resource that describes the process in more detail? Or can anyone explain the two steps I mentioned above? Or do I just need to buy a factory service manual? I found the FSM's on ebay for 180 bucks, but that is pretty pricey.

Thanks

Jared

Mr Jokster

iTrader: (8)

Its like just 4 screws man, VERY easy.

Marking the TPS? Nah, for noobs. Just reinstall and start the car, if its idling too high, turn it clockwise, idling too low, turn it counter-clockwise (or visa versa, cant remember). As soon as you loosen the screws on the TPS, you'll see it move slightly. When you remove it, you'll see a couple tabs on the inside that are spring loaded. Thats why it needs to be marked so that you put it back in place, however, it will still need calibration because where its set is to work with the current motor and APPS, the new motor will make it slightly off. This is why imo marking is pointless because you have to adjust it anyways. The spring tabs apply pressure to the butterfly of the throttle body which opens and closes it ever so slightly to increase or decrease idle.

As for the codes... Highly doubt its the motor. Almost all of the time its the APPS.

I didnt watch the video, too long... Not sure if it was mentioned in the video, but my advise, make sure the "tabs" on the TPS are on the correct side of the "tabs" on the throttle body, if they're not, you wont be able to adjust it. The tabs on the TPS have springs on them and if on the wrong side of the throttle body, you wont be able to adjust the butterfly. You'll know right away when you place it over the throttle body. As soon as you place it on, give it a little twist, you should be able to feel the 'springyness'.

The screws holding the motor/cover on are most likely going to be extremely tight, be sure not to strip the heads. If you see that they're not coming off easily, I suggest using a set of vice grips to 'break' them loose before unscrewing.

The job is VERY easy, dont fret, no need to buy a repair manual. Just look at the part and look for the screws/bolts that are holding it in place and remove them. Just like removing a tire, you see 5 lugs, you remove 5 lugs.

sjpitts

Mr Jokster

Thanks much for the advice. You having given me a bit more confidence on this. It doesn't sound too bad.

However, I must admit that I didn't really consider that it could be the APPS. I may have jumped the gun on replacing the motor. Is there a definitive way to tell without just replacing the parts?

The car has been having issues with the AC servo motors, and I thought I heard a similar sound when it went into limp mode. But that could really have been anything. It could have been my imagination.

Thanks again,

Jared

Mr Jokster

iTrader: (8)

The sensor is quite easy, you can use a multimeter, ground the meter and put the other end to the signal wire on the sensor (you're gonna need 3 hands). Once you get your initial reading, you have to slowly open the throttle by hand and watch the meter. Without getting too technical, basically you should see the numbers slowly climb like 1, 2, 3, 4, 5, 6, 7 etc. A defective sensor would show something like 1, 2, ..., 1, ..., 5, ..., 7 etc. Or something to that effect showing that as the throttle moves, its missing sequential values on the way up thus the reason why the car will hop and skip.

burny

https://www.clublexus.com/forums/per...mp-mode-4.html

Read through this thread. It is long, but very detailed. There is a PDF attached to one of the posts that shows the normal ohm readings for the TPS, TCM and APPS. I used this to diagnose the Throttle control motor as the issue and replaced it. Car is still going fine. Be sure to put the wire in the holder next to the TCM when replacing. If not the wire will be too close to the manifold and eventually cause failure again from the extreme heat.
When reading the thread, I would concentrate on the areas where Lexus is fixing this issue for free and let them deal with it.

sjpitts

OK, maybe a dumb question, but these values (1, 2, 3, etc), are they ohms? And you can measure them with the sensor on the car, but the car off?

Or are they volts, and the car needs to be on and running?

It seems like they would just be ohms, but I want to make sure.

Again, sorry if that is a dumb question.

Jared

sjpitts

Wait, I think I found a picture showing how to do this. Ohms it is.

sjpitts

Thanks, I haven't found a PDF, but I found the picture I just posted above. I am not sure if the settlement is still active. All the links I tried were dead.

jared

Mr Jokster

iTrader: (8)

Your diagram is the correct way to do it, I just couldnt remember the proper impedance values, so I gave the voltage way to do it.

As for the settlement, checks have already been sent out. You needed to be the current owner when the settlement occurred.

burny

I would read posts 515,518,528 and 542 in the thread I linked. Call Corporate and let them know you are experiencing this serious safety issue and need it repaired.

sjpitts

So I just did this test. I put on my ohm meter and I measured 1.7kOhms. That is right in the range that it supposed to read. But then measured the ohms while rotating the cable-- I rotated it clockwise, emulating what would happen if the accelerator cable was being pulled --- and nothing changed. I was expect the ohms to change when that rotated.

Was I wrong about that? Or does this show that something is wrong with my APPS? Maybe I rotated the wrong thing?

Thanks again for your help

Jared

sjpitts

OK, let me try to explain what I did one more time. I measured the impedance betweem E2 and VC. It measured 1.7kOhms, which is right in the middle of the expected value.

I then rotated the part of the APPS where the cable attaches while measuring the impedance. I rotated it as shown in the attached figure. I was expecting to see the measured impedance change while I did this. But it never changed.

What does this mean? Does this mean there is something wrong with the APPS?

Or was I testing it wrong? I am not sure that the impedance would really change when you rotate where the cable attaches, because I am not sure the APPS really has anything to do with the cable.

So can you clarify?

Thanks

Jared

Mr Jokster

iTrader: (8)

You're doing it just fine. No change in the readings would indicate no input from the throttle position sensor. It would seem that the APPS is the culprit.

Heres a video giving what I would expect the "professional" procedure to check.

sjpitts

Thanks for the reply. It appears that I jumped the gun buying a 270 dollar throttle control motor from Toyota.

So now that I need to buy an APPS, should I pay the extra and buy OEM?

On ebay, there are complete OEM APPS's for 180.00. There are some generic looking ones from china for 95.00. And there are some that don't include the spring and cable part for 132. What do you recommend?

http://www.ebay.com/itm/NEW-FACTORY-...lWtZvL&vxp=mtr

http://www.ebay.com/itm/New-Throttle...NX9Mqw&vxp=mtr

http://www.ebay.com/itm/OEM-For-Lexu...xYfW6F&vxp=mtr

Thanks again for the help.

Jared

lexo98

iTrader: (2)

Are you sure the throttle position sensor is properly installed? It doesn't just slide straight in. The tabs on the inside need to be angled so that it will control the throttle. It's hard to explain but when I cleaned my throtttle body I had removed it and didn't reinstall the tabs so they were lined up and felt spring loaded and my car didn't run. I freaked out until I figured that out. If it doesn't feel spring loaded, when you measure with the ohm reader and move the tps the ohms will not change