Hello. Let me first introduce myself. I'm new to CL. I purchased my 01 LS430 in 2013. I've been browsing the website for quite some time and I'm honored to be apart if Team Lexus now. Here's my issue.

I've researched this acceleration issue on these forums and I wanted to know if anyone had any additional information.

If I'm driving anywhere between 50-80mph and I floor the accelerator, the car doesn't accelerate. It just feels like the tranny is still in 5th gear. It just pulls slightly and doesn't accelerate like it's supposed to. I know the tranny is supposed to automatically downshift to somewhere like 3rd gear to get more power, but it stays in 5th gear.

When I keep it floored, the tach jumps a bit like it had switched gears, but still no significant power. I've cleaned the MAF sensor and still nothing. Yes, the CEL is on. It goes off and whenever I try to replicate the problem, it cuts back on.

I got the code pulled at the mechanic. He says is a P0430 code for a bad catalytic converter, but I've been had bad cats and never had this issue with accelerating.

I was researching the issue and came up with it either being an Accelerator Pedal Position Sensor, maybe a fuel pump, a fuel injector, a bad computer for the tranny, idk.

What was everyone's issue and solution to this please.

 

Check with the folks on the post below... Your problem seems to be tranny-related.
https://www.clublexus.com/forums/ls4...s430-base.html
A couple of questions - Was the battery disconnected days prior to pulling the error code? Was P0430 the only one?

 

Thanks for the reply. No. The battery has not been disconnected. Right now, the CEL is on. If I drive around for a few days, it'll cut off. I did have that issue where if I'm driving on the highway and my foot was on the accelerator, it felt like I took my foot off the gas and I wasn't accelerating. Almost like an immediate stop of accelerating. Gears didn't change then. Once I took my foot off the pedal and reapplied it with more pressure than before, I would return to normal coasting. That would last for maybe 3-5 seconds. It would happen maybe twice on a 30 minute 40 mile drive. Anywhere between 0mph and 40mph, I have no issues with accelerating and the gears cycle correctly.

 

The LS430 ECT is very sophisticated - it takes input signals from multiple systems to determine shift behavior. Shown here is a diagram for the 2004 LS430. I'm not sure if this is different for earlier models. If you're sure that CEL only yielded the one error code P0430, then I would suggest to disconnect the negative battery cable for 10-15 minutes to reset the ECM to factory default settings. Sometimes by resetting the ECM, your car may detect additional error codes.

 

Thanks for the diagrams. Those look interesting.

That will be my next step tomorrow is to remove the negative cable from the battery and see what happens.

I will be sure to post an update.

Thanks again!!!

 

Find someone with Techstream to narrow down the problem so you don't have to guess randomly. Otherwise, you can measure each of these components manually and replace if they do not meet spec. From most likely to least likely: accelerator pedal position sensor, transmission speed sensors, throttle position sensor, MAF, throttle control motor, crankshaft position sensor.

You mentioned you cleaned the MAF - was the problem equally bad or even worse prior to cleaning the MAF? Maybe your MAF didn't survive the cleaning. Also, ensure all vacuum hoses are connected and leak-free.

Regarding P0430, it is almost never a problem with the catalyst. All LS430s over 10 years old and exposed to salt/water will develop a small exhaust leak at the Y-pipe gasket and/or underneath a heat shield. As I mentioned at https://www.clublexus.com/forums/ls4...ml#post8762221, the Y-pipe / P0430 is an expensive problem if you wait too long to fix it, and it could have been avoided completely if action was taken early enough.

Everyone with an LS430 that drives on salted roads or lives near the ocean should remove both the heat shield clamps and the heat shields immediately. Otherwise, you have a 100% probability of having an exhaust leak and seeing DTC P0430 in the very near future. If you catch the problem early, you can fix with a $5 tube of JB Weld. If you're past that, then you'll need to spend ~$30-50 dollars for an actual weld. If you're too late, you're going to spend hundreds of dollars for a new Y-pipe.

 

I'm a pretty well versed mechanic, keep in mind there are a lot of redundent systems in luxury cars, Lexus is no exception. It took me a very long time to solve my transmission problem, because of this. Without inspecting the electronics, and wiring in each of the systems that control shifting, you're at the mercy of the ECM detecting an issue and throwing a code. I kinda forced mine to throw a code by beating on it when the tranny wouldn't shift instead of limping it back home like I normally would. I don't recommend doing this, unless you're prepared to deal with any consequences.

I would get someone to pull codes one more time, before you reset the ecm. Ask that person to check for stored codes. Hopefully you'll have another code.

A link to my thread was posted, I would read it carefully. I had a very specific issue, the best way to describe my problem is erratic shifting. Your problem sounds like no downshift. I'll post some info that should help you shortly.

The issue you're decribing points toward the transmission control switch circuit. I would call your local lexus/toyota parts desk and see if they would print out the section starting at page DI-246. The diagrams posted before me are for a 6 speed transmission, so I don't think much of it will apply to your 01 ls430 with a 5 speed.

 

P0430 could be exhaust leak near the rear o2 sensor as stated earlier. P0430 is passenger and p0420 is driver side. Remove the heat shield and inspect. I had this problem before, I had cel, trac off and vsc lights on. Car was also very sluggish, has problems with shifting. Found exhaust leak, cut out section and welded in new pipe. Disconnect battery and problem solved, it never came back.

 

Here's some paperwork I have that will at least get you a head start.

 

This is all great information. Thanks so much for your help!!!

The update is it hasn't happened since last Friday. All I did was respray the MAF, let it dry, and put it back on. I do notice a bit of an improvement in response and acceleration. It has also not thrown a CEL code.

I will take it to my mechanic and have them inspect the gaskets for any seals. I didn't know that $5.00 dollar tube of JB Weld works wonders. I will check that out.

But as of today, no issues luckily. Someone told me the ECU probably had to relearn my driving habits after I cleaned the MAF.

I do appreciate your responses.

 

For the record, I don't condone the use of jb weld...

 

Hey Bud,

I saw your invoice location, and i'm all hey, thats my stomping grounds. I live about ten minutes from Lexus of Sacramento. There's a couple of really good indy tranny shops in the Sac area. I think you could have saved some money avoiding the dealer. I go there mainly to pick up parts for my indy mechanic, and the free donuts, coffee
If you need any shop names, feel free to inbox me

 

Haha I didn't actually buy all those parts. I'm actually was a mechanic here in town. I'm an engine builder now. I'd buy a used tranny before spending that kind of money repairing my old one.

I did really like the dealer. Who can complain about free coffee? I'm pretty much up to 3 starbucks visits every day now haha.

I did stomp my way out of the dealer sarcastically yelling out "Oh the joys of Lexus ownership!"

 

I was having the exact same issue with my 01 LS430 (230k miles) recently. Pulled the MAF and cleaned it, no change. Still had sluggish acceleration. So I replaced it with a Denso one from Amazon for $75. Fixed the acceleration issue.

Replacing the MAF should be a maintenance item. You can only clean it so many times before you just need to replace it. Takes 5 minuted to replace.

I don't know how many miles you have on your car (you may want to list that very pertinent piece of information) but if its anywhere north of 100-150k, just replace the thing.

 

I originally cleaned it twice and it had te same issue off and on. I got a throttle body cleaning and luckily it hasn't done it since. That's crazy how the MAF will stop working and it just needs to be replaced. My next step was to have the Throttle Position Sensor replaced. That looked like it was a part connected to the actual Throttle Body.

Thanks for all of the input.

BTW, going to the Lexus dealership is absolutely amazing. It's almost like a luxury cafe with everything you want or need. We have the same type of service at ours here in Washington DC.