loud3nergy

This has been happening to me lately. I have a 99 GS400 w/125k miles. Ill be driving and then the CEL and VSC lights come on and have no throttle response for the first 80-90% of the gas pedal range and then it goes to the back-up cable response. I have done many searchers on ClubLexus and most have pointed towards the TPS and PPS sensors. So to narrow it down I took it to the local toyota dealer (closest Lexus dealer is 1.5 hrs away) and ran a diagnostics test on it. It was showing that it needed a Catalytic converter and they quoted me a price of approx $1300. My question is, would the catalytic converter really cause these symptoms if it was faulty? I have owned the car for 6 months and have only used Shell or BP premium gas. Any insight would be priceless right now. Thanks!

GS_OREO

A clogged CAT can cause backpressure which can cause misifires.

loud3nergy

would that trigger the car to go into 'safe' mode?

Debonair

What DTC(s) was setting the CEL on?

loud3nergy

P0340 bank two catalyst efficiency below threshold.

Debonair

P0340 is not a CAT code, its a Camshaft Position Sensor code.

Did you mean P0430?

P0430 is a CAT code stating that the CAT is not performing. This could be a clogged or failed CAT, Gas leak, or any of the Oxygen Sensors.

If these symptoms do not happen until after the car has warmed up then they probably are related to the code as the car does not check for this issue until then.

Was there any other codes or was this the only one?

loud3nergy

Well replaced some parts and have done some more research with out any progress... replaced the TPS sensor on the throttle body along with the Throttle Body Lever Sensor (what the actual cable wraps around) Still having the same issues. Car does it all the time now, it never acts right.. symptoms include:

-No throttle response except for last 25% of throttle
-Ideling high, around 1100 RPM
-When shifting it will shift late and very hard jerking the car and most times chirping the tires going from 1st to second.
-CEL, VSC and VSC OFF lights are always on

****anyone else having the problem please help me as with what resolved the issue for you.****

Thanks!

whazzzzuup

iTrader: (11)

Sounds like a MAF issue. Clean the MAF and see what happens. Sometimes, that would work. If it doesn't, then MAF replacement would be the next step. People on the Maxima forum always have the symptoms when their MAFs become defective. The defect is generally caused by the oil via the aftermarket K&N filter. Good luck!

loud3nergy

well, cleaned the MAF today and still no luck.. Also no K&N filter this GS is completly stock. Also took the cats off and inspected them.. they are still good. Might try and replace the MAF next... Any other suggestions? Thanks!