Hello everyone, I am new to this forum and need help. To start I don't own a Lexus, but my girlfriend does and that is where my problem lies. Just about three weeks ago she began complaining of CEL's and other warning lights coming on just before she losese the ability to accelerate(limp mode from what I understand). Now this does not happen daily but in the last week has become much more frequent of an issue, so I obd it, P1120(accelerator pedal position sensor?) Anyways yesterday we take it to the dealer and they call saying they need a new ECM to the tune of $3k, before they can check the sensor which would run another $700.. In short are they trying to take advantage or is this common troubleshooting? I appreciate any help, and have read several threads pertaining to trouble code P1120. Thank you in advance.

 

instead of taking it to the dealer take it to some small mechanic shops, im sure they wont charge that much. try cleaning the throttle body.

 

First off what is the year and model of your GFs Lexus?

Replacing the main ECU is not a common troubleshooting FIRST step. That said if they have already eliminated the Accelerator Pedal Sensor and sensor wiring as the cause, the ECM is the next culprit on the list.

Read up on this code HERE as MANY members have already got and fixed it.

 

This thread specifically helped me with my troubles.

 

So what was the conclusion of your problem?

 

First off its a 99. So got the lexus back yesterday and they said it was just a faulty ecm. So there's 2k, this morning we were driving home and when turning to cross an extremely busy highspeed street boom "limp mode" and nearly get clobbered by a huge turbo diesel. So now faith in the dealer is almost nonexistent. I am going to check for trouble codes again. But the same symptoms have re-risen within 24hrs(cel, vsc lights, etc.) After code checking should I go through and check voltage? And if so can anyone give correct voltage/ohm reading I should get? Thank you all for help so far, we cannot afford another hit like this so again thank you.

 

you payed 2k and the problem still exist? take it back asap.

 

Sound like she needs to find a richer boyfriend...

j/k -----

Seriously though, it sounded like your TPS or Throttle Motor is the issue and Thomas had showed you where to go start your research, but you then just spent $2,000 at the dealer anyway. So I'm not sure what else you want to know now? Unfortunately your now going to need to go round-and-round with the dealer as they have alot of your money and the car still does not run.

You start messing with it on your own at this point and they can just say you've screwed something up, and voided any warranty you would have had on their $2000 attempt. You need to either pursue a full refund first and then try to fix the car yourself, or let them keep your money and force them to continue working on the car until it is fixed.

And btw most dealers will not want to listen to the customer telling them what should be done to fix it as per some forum info..

Sticky situation now man, sorry to see...

 

Which stealership did you take it too? Man I would take the SHT back so fast.

 

OK so here's the deal. That code is very very common. it is always the accelerator position sensor. sometimes throttle position sensor is sold also, only because they typically fail at around the same time.

I do not for a second buy the engine computer went bad. we almost never have problems with that computer.
Here's the deal. Lexus troubleshooting guides fool "less talented" technicians. the repair manual for most codes will have you check voltages at pins and resistance of different components. WELL GUESS WHAT? if all that checks out....the last step will say "replace ecm"......makes sense...if nothing else is wrong....it must be the computer. WELL GUESS WHAT?????? The problem you described is a very very very intermittent problem. Almost any time you go to check voltages and resistance, THEY WILL CHECK OUT OK BECAUSE THE PROBLEM IS NOT HAPPENING AT THAT TIME. A half experienced tech would know that. But people mess it up all the time.

Get your money back. You spent money on a problem and it wasn't fixed. at least 99% of the time that code is the accelerator position sensor. should run about 400-450 for the part. I'd be mad if I were in your shoes. I might ask for more than just the 2k back.......

 

FYI, the problem only happens for a split second....then goes into fail-safe mode. the problem is not continuing the entire time it's in fail-safe mode. It just won't leave fail safe until the key is cycled

And if you care to know what the problem is.....I'll give you the super short version. the accel position sensor actually has 2 sensors in it for safety reasons. when the 2 sensors don't agree on the position, it shuts down the system and throws the code

 

It's your Throttle Motor. I just replaced mine also. You can buy the Throttle Control Motor from Sewell Lexus with a CL discount for a little over 200 and replace it yourself.

 

I have no intention of being argumentative. I just don't want someone to buy a throttle motor based on an accelerator position sensor circuit malfunction code. I gave the short version of what causes that code and don't feel like typing the long story. so I'll copy and paste a little bit and be done with this.

Accelerator pedal position sensor is mounted on the throttle body and it has
2 sensors to detects the accelerator position and a malfunction of the accelerator position’s own.
The accelerator pedal position sensor is connected with the accelerator pedal by the accelerator wire and
the voltage applied to terminals VPA and VPA2 of the ECM changes between 0 V and 5 V in proportion to
the opening angle of the accelerator pedal.
The ECM judges the current opening angle of the accelerator pedal by these signals input from terminals
VPA and VPA2 and the ECM controls the throttle motor based on these signals.
If this DTC is stored, the ECM shuts down the power for the throttle motor and the magnetic clutch, and the
throttle valve is fully closed by the return spring.
However, the opening angle of the throttle valve can be controlled by the accelerator pedal through the throttle cable.

that was the beginning of p1120, i'll skip to the end to show what i was referring to in an earlier post.

check and replace ECM (See page IN−32)