Check Vsc

[brian155]

Hi All,

As in topic title my car is GS430 2005 with 99000 miles on clock and the check VSC warning as come on

along with yellow slip indicator light, yellow brake system warning light and yellow engine sign also when these are lit up I cannot engage cruise control. This was a known fault when I purchased the car

4 months ago but the then owner told me he took it to be checked and there was no fault stored in the vehicle memory and that the day to day running of the car was not affected and the lights etc were put out. Since that time the lights have come back on around 4 times and iv'e put them out with a code reader I bought and to be fair I don't notice any difference in the performance of the car. The fault code is P0420 and I get 2 "pages" both saying catalyst system efficiency below threshold (bank 1).I have been reading via google search about this fault code with various "fixes" from "cataclean" to wanting new oxygen sensors to leaking injectors to needing new cats, is there anyone on here that can help with a cure before a go down the OMG how much Lexus dealer route. The lights come on after a random mileage ranging from 8 miles to nearly 100 miles, also I do very short journeys of around 2 miles per day up to 10 miles a day will this have any effect on the cats getting warm enough to do their job?.

Kind Regards for your replies

Brian.

[steve2006]

Given the code I would consider having the car checked by a decent garage with good diagnostic equipment which can perform "live data" checks.

This will provide a more accurate diagnosis and will check the operation of the O2 sensors both voltage wise and switching frequency.

This doesn't have to be a Lexus dealer but make sure the one you choose has the necessary skills and equipment to do the job with preferably Lexus/Toyota trained staff.

[brian155]

Thanks Steve for your advice there is a really good auto electrician up in Stoke On Trent called D J Auto's and iv'e been told what he doesn't know about diagnostic's ain't worth talking about so will give him a call in the new year, thanks again for your reply.

[ColinBarber]

The lights come on after a random mileage ranging from 8 miles to nearly 100 miles, also I do very short journeys of around 2 miles per day up to 10 miles a day will this have any effect on the cats getting warm enough to do their job?.

The ECU knows not to check until everything is up to temperature, that is why you are seeing the light only come on after 8 miles. This fault is generated by the ECU monitoring the downstream O2 sensor, it should detect slow moving voltages. It is rarely the sensor that is at fault, with age these sensors tend to get lazy however we are only looking for slow voltage changes so ageing doesn't tend to be an issue.

Typically this fault can be caused by three things:

The upstream sensor causing the engine to run slightly rich/lean

An air leak in the exhaust near the downstream O2 sensor

The Cat isn't operating efficiently.

It should be possible for a garage to diagnose this correctly without having to replace parts. The fact that you have a V8 with two banks makes it easier because you can compare the two.