SpencerT

On my 95 ls400 the check engine light is on because of an 02 sensor.

Im not sure of the exact code but I believe it is a downstream sensor.
A shop I trust thought it was due to an exhaust leak immediatly after a catalytic converter that was tripping the o2 sensor.

When I cleared the codes the sheck engine light would come back on within 50 to 250 miles under normal driving, but will come on within 5 miles if I put the car in power mode and really floor it to 80mph+

After 1.5 years of driving like this I finally got the leak fixed (The shop disconnected the pipes and installed a new gasket after the catalytic converter) and it deffinatly sounds like the leak is fixed as the tick is gone and the tone is much deeper.

200 miles of cautious driving later and a coworker shows up to work with a 2012 impala (Same model as the cops) and talks all day about how his rentel chevy will blow my lexus away.
Needless to say, after that LS400 POWERRRRR video, I was curious.

0-60 he had me. barely.
after that my 18 year old lexus past his "300hp" impala and easily gained ground until i hit 95 and had to slow down.

I was thrilled until the check engine light returned 2 miles later.



Long story short: My 02 sensors trip the cel at full throttle.
Ill post the exact code in a day or so.
until then any ideas?

billydpowe

iTrader: (1)

not without the codes, for me.

whit3b0y

only thing i could think of is, don't go 95MPH. there is no need to.

SpencerT

I considered that. It is more of a want than a need.


btw the check engine light will come on regardless.
It just does it much sooner when I go that fast.

GS4_Fiend

iTrader: (22)

Well retrieve the code by looking for the DLC connector under the hood, short Pin TE1 and E1 with a paper clip and count the CEL flashes. Make sure you got no exhaust leak. Report back

SpencerT

Why does everyone recomend shorting Pin TE1 and E1 with a paper clip and counting the CEL flashes?
the 95 is obd2 and pretty much every single auto parts store or oil change place will let you use a scanner for free.

The code is P0430. catalyst efficiency below normal. bank 2.


On a possibly unrelated note: today while idling in drive around 400 rpm (factory ecu problem I believe) and when I turned the ac on the engine revved up to 650 rpm like normal, then the ac sounded like it was being cut on and off rapidly and the rpms bounced from 400 to 650 about 5 times before the ac fully came on.
I turned the ac off then back on and the problem was gone.
Was this just a fluke do I have another problem?


So now I have 2 questions.
The cause of my check engine light.
And what the heck was happening with my ac?

Lavrishevo

iTrader: (1)

I just dealt with the same thing on my 99, but it was code 420 bank 1. 430 - Bank 2 is passenger side. Check for exhaust leak at the down pipe, could be post cat 02 sensor, and if not any of those it will be the cat. Have to replace both. Mine turned out to be the cat on bank 1. Kind of sounds like exhaust leak. If not, it is probably the cat. Lexus said that the 02 sensors will set their own specific code when I was researching my problem.

When I reset my ecu the idle rpms were a little off but came back to normal within 100 miles of driving. Clean your throttle body if you have not already.

GS4_Fiend

iTrader: (22)

P0430 - check for exhaust leaks, bad post o2, lastly bad cat.

SpencerT

the code came up on the scanner as catalyst below thresh hold.

doesnt this mean that the downstream o2 sensors are reading the air mixture and must be working?
I thought a dead o2 sensor gave a different code.

the exhaust smells rich too if that gives any clues

PureDrifter

iTrader: (10)

please pay attention to the year of the vehicle being posted

OP-hunt for exhaust leaks and check the exhaust for O2 content.

Lavrishevo

iTrader: (1)

Since 420 & 430 are generic codes your going to have to do a process of elimination. It's the passenger side that your getting the error on. The post cat 02 sensors reading vary to much compared to the pre. Personally, I would check for exhaust leak. It only needs to be a very small leak to set the code. If no exhaust leak then it's either the sensor or the cat. My bets are it's the cat starting to degrade. I don't believe 02 sensors are returnable item. The other idea, although this may sound crazy but you can swap the bank 1 & bank 2 sensors, reset the code, and then see if it comes back as PO420. This would tell you it's the sensor. Again, if no leak and it comes back as 430 and you swapped the sensors then it's the cat. No, the downstream 02 sensor is for emissions.

Another piece of advice is to test for exhaust leak while someone is reving the engine a bit. Small leaks may not leak unless under pressure.