AnthonyZ

2000 gs400 died 2 days after buying it. Vsc off lights come on and nothing but the mechanical throttle. Got codes for the apps and throttle control motor circuit malfunction. Fuses seem good. I replaced the apps from autozone and that got rid of the apps code. Now just the throttle motor. I was able to test the motor and see that it does get power and opens when I use a power probe. I brought it to Lexus for what I thought would be an expert opinion and I get a call within an hour saying it’s the throttle motor, I don’t think they checked very hard or at least as hard as I would have liked. Whatever. Estimated $2100 for entirely new throttle body as Lexus doesn’t sell just the motor. I got it off eBay for $350ish. Installed it and what do you know… same thing, limp mode and no throttle response. Swapped in a new tps just to check and still same results. Throttle control motor circuit malfunction. At this point it seems like the only thing left to replace is the ecu. Do these things go bad that often? I do not feel like dumping more and more money into this car that I’ve only been able to drive for 2 days. I’d like to hear other opinions on my situation or any info that you may find helpful it seems every thread on this topic is just a dead end. Also the throttle motor turns on when the car is off and as soon as I pull the throttle cable it turns off? Any clues what that could mean?

Arussto

Update on rereafing your post. I now know ehat apps means😂🤣 so deleting my rant or editing
By apps you mean the thing on the TB where the cable attaches to?
That does go bad as the solder sometimes goes cold .
Symptom is no response to pedal from about the first quarter inch to the last quarter inch .
like a dead pedal for about 60 percent of the pedal travel.
kindly verify. That part i think is called the accelerator pedal position sensor.

The motor on the TPS side of the throttle body rarely if ever goes bad from my reading.
Why not put ignition on and see if butterfly is operating wuth pedal?

If indeed that is uour symptom, search CL for:

GS300 '03 3L Accelerator Pedal Sensor

Matt 222 I think is originator.

Hope this is your problem as easy fix.

Yri

Is your scanner good enough to be able to read live data from the car? If so, check the throttle position percentages and see if they act accordingly to your pedal inputs. Considering you've replaced the TPS, it should have gone away by now. Check your connectors to the throttle body itself. If they're dirty it can make a difference too, maybe follow the wires back and check other connectors too.

EDIT: I did just find this video on a GS400 that seems to have a similar issue...

AnthonyZ

Hey thanks for the responses, I’ve actually been using that video as my reference and I seem to be getting the same exact results as him. I’ve just gone out and tested apps, tps, and the motor, all come out great. Voltage gets put out consistently from the apps when the cables pulled. But no movement from the throttle plate. Motors ohms read 0.4 right in spec. The entire throttle body is new after all. I’ve inspected the wires not very much just visually and tugged on them through the harness a bit. Everything seems good to me… I’ve used the scanner to read the live data and tp% does not change when the pedal is pressed. But the tps is connected to the throttle plate through small gears so it doesn’t surprise me as my throttle plate isn’t even moving. I am thinking it’s the ecm, I got the service manual and have been through all the steps with all components testing to be fine pointing to either wiring or ecm. Voltage goes from the apps, to ecu, which then tells the motor. I’ve verified that the signal goes from the apps to the ecu. My cars throws a code for the throttle control motor even though it’s in working condition, could this be the ecu’s fault for not sending the right info to the motor for it to work properly? I’m thinking I’m in the same situation as that video

AnthonyZ

Maybe these can help somebody else

AnthonyZ

Hey just an update, I replaced the ecu and it works again! It seems to work so much better than when I had first drove it 😁