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I own a 05' Lexus LS430 and I had been having such a headache lately for which I am going to need your guys help to figure out the problem.
Recently over month+ my vehicle would sometimes jerk/hesitate/delay when I give an acceleration in P/N Gear and sometimes when I drive for a good amount of time inside the city with A/C on or keep vehicle in start idle for long time without movement and I turn off the car then when I start the car won't start instead It would simply crank and then I have to let the car be off for 2-3 minutes and then when I start it would start right away. There had been also times where when I cold start in the morning the vehicle would randomly start in "LIMP MODE" where the engine would be very rough/jerky with fuel smell all over the air and accelerator pedal won't respond at all and car speed would be limited to 10/20 speed max with jerky RPM vibrations and only solution would be to turn off the engine and wait few minutes and start again then It would start normally and smoothly no vibrations. In other hand when I drive the vehicle at night and park the vehicle and turn off the front parking lights then immediately the RPM will drop too low as soon as I turn off the lights and sometimes even engine would turn off by itself such as the picture below (Idling at 100-200 RPM) :
Sometimes when idling there is miss fire feel in the vehicle like random slight low jerk.
At times most commonly I had CEL/VSC only with code P0121 Throttle position (TP) switch A/accelerator pedal position (APP) switch A - range/performance problem - Status: CONFIRMED
After facing the same problem multiple times I thought It could be issue with the Sensor in the Accelerator Pedal hence I replaced the whole accelerator pedal with sensor from a vehicle in nearby Junkyard and after the replacement the vehicle ran for 1 good day and then the same problem. But a day later I am thrown with new multiple CEL/VSC codes such as along with previous P0121 :
P0122 Throttle position (TP) switch A/accelerator pedal position (APP) switch A - low input | Accelerator Pedal Position Sensor / Throttle Position Sensor A Circuit Low Input - Status: CONFIRMED
P0222 Throttle position (TP) sensor B/accelerator pedal position (APP) sensor B - low input | Accelerator Pedal Position Sensor / Throttle Position Sensor B Circuit Low Input - Status: CONFIRMED
P2135 Throttle position (TP) or Accelerator pedal position (APP) sensor / switch A/B - voltage correlation - Status: CONFIRMED
And sometimes randomly every time I change the parts back and fourth I am greeted with this code which lasts only one time and doesn't come back after clearing until I replace throttle parts again because I decided to put back old my accelerator pedal along with it's sensor today.
Now I am really lost and don't know what to do. I tried clearing the codes and they go away but a day later they come back again (Except P0500) with the Junkyard Pedal + Sensor Unit. Now today I replaced back with my old Pedal and sensor and I am greeted with P0121 only randomly and at times It goes away itself and hopefully the other set of codes don't come? or maybe they will? don't know only upcoming days will tell. Not sure if I messed up anything :-(
And so far I have tried cleaning the MAF sensor with IPA 70%, Cleaned Throttle Body with Throttle Body cleaner, Spark Plugs + Coils and only thing I can think of now replacing the whole Throttle Body unit but I am not sure if I should because I heard people say the Throttle Body of LS430 won't easily go bad. I did previously once trying swapping the whole TB unit with a Junkyard one a LS430 2004 and I was greeted with ABS warning light as soon as I turn on vehicle then I didn't try driving with it instead fitted my old one back the same minute because I didn't want to risk and with my old (current) TB unit I don't have any ABS lights.
Needs a new battery. Also check that the battery is charging correctly (over 14 volts with the engine running).
A 05 LS430 has an alternator which has a charging control function and the stronger temperature compensation. So it's not always 14V even the engine is running. The ECU is always monitoring the voltage and the current. When the battery is well charged, the alternator's voltage drops down to 13V or a bit less.
Throttle/Pedal Sensor Issue
and only thing I can think of now replacing the whole Throttle Body unit but I am not sure if I should because I heard people say the Throttle Body of LS430 won't easily go bad. I did previously once trying swapping the whole TB unit with a Junkyard one a LS430 2004 and I was greeted with ABS warning light as soon as I turn on vehicle then I didn't try driving with it instead fitted my old one back the same minute because I didn't want to risk and with my old (current) TB unit I don't have any ABS lights.
