BristolBrian

Well, no re-occurrence of the light since then and frankly, I had forgotten all about it when I took it into the garage for a service and MoT this morning. Two hours later I get a phone call telling me it's failed its MoT for a hole in the exhaust! Mystery solved, I think.

Techstream runs on Windows only as far as I am aware, so I think you might be stuck....

I think I paid about £25-30 for a OBD2 connector widget with a cable terminated in a USB which plugged into my laptop, it also included the software and a licence key for it. I've just checked ebay and the seller I bought it from is no longer selling them. I recall something about Techstream V13 might not have needed a licence key, but doesn't work on Win10, I have Techstream V15 which works fine.

If that's asking me Ian, then frankly I didn't resolve it, it pretty much resolved itself. All I did was plug in Techstream (the Toyota/Lexus diagnostic app - see eBay) and clear the warning light and the associated error. From my understanding from reading around: - check your exhaust for leaks, particularly around joints, but also any tiny holes. - check the O2 sensors are working ok (see Lwerewolf's post above), if problems then it's likely the front sensor (P420 = left, P430 = right) If those are all ok, it's probably the cat, don't replace with a cheap one, it'll likely retrigger the same code, possibly even from new. That's all for a 2005 GS300, your 2000 GS430 may be different.

Just an update in case anyone finds this later - I've now done a couple of slightly longer trips, up to about an hour including motorway and accelerating hard up to motorway speed and the light has stayed off. Fingers crossed it was a blip, but I'll get the garage to double check the exhaust for leaks when the MoT comes up in Feb. Thanks for the help, particularly Lwerewolf.

Thanks for that very comprehensive summary - that's great and exactly the explanation I was hoping for. I must have missed something when I tried to reset the warning light in Techstream the first time as I tried again on Saturday and (so far) it has stayed off. I'm going to cross my fingers for the next couple of weeks and see whether it comes back on again once I've done a decent trip, as so far all I've done are a few half hour round-town trips. If it does come back I'll definitely follow your suggestion and map out the response to see if it really is the cat or not. Hopefully not !

Thanks for the replies today. I did see the thing about the fuel cap and had a fiddle with it yesterday. The cap seemed to be pretty solidly attached with no play when attempting to move it around. I think I might ask my local garage to check the exhaust in the next week or so, and see if that helps. In the meantime, I've ordered some cataclean just in case, and might just get a new fuel cap on the same basis. Both of those potential solutions are way less than an hour's labour! If anyone can help interpret those Techstream readings, I'd be most grateful.

The lights have been on solidly since they pinged on for the first time yesterday, and even clearing them in Techstream made no difference. I have no idea what that implies (!) but maybe someone does!

I've had an early GS300 Mk3 for the last 3 years and apart from a few minor things, it's been great. Yesterday however the dreaded 'Check VSC', TRC and engine orange warning lights came on. I plugged Techstream into it and downloaded the data and it seems to be a Cat Efficiency error - or at least that's what is showing. The O2 sensors and O2 sensor heaters show as Pass. Reading around this forum (thanks!) I think I interpret this to mean one of the following: - O2 sensor failure, probably front, or - Exhaust leak, or - Cat starting to go. Is that reasonable? There is 107k on the car. Clicking into the various Techstream bits I found the following: Monitor Cumulative Result Summary Misfire Available Infinity Fuel System Available - Infinity Composition Parts Available - Infinity Catalyst Efficiency Complete Fail Thumb Down(Red) Heated Catalyst N/A - N/A Evaporative System N/A - N/A Secondary Air System N/A - N/A A/C System N/A - N/A O2 Sensor Complete Pass Thumb Up O2 Sensor Heater Complete Pass Thumb Up Exhaust Gas Recirculation / VVT N/A - N/A Thermostat - And then on the "Test Results Report" Test Result Min Max Test Value Unit O2 LEN B1 A Pass 0.00 18.83 1.85 V O2 LEN B1 B Pass 0.00 0.00 0.00 V O2 LEN B1 A Pass 0.00 0.00 0.00 V O2 LEN B1 B Pass 0.00 0.00 0.00 V O2 LEN B2 A Pass 0.00 0.00 0.00 V O2 LEN B2 B Fail 0.00 26.20 28.84 V O2 LEN B2 A Pass 0.00 0.00 0.00 V O2 LEN B2 B Pass 0.00 0.00 0.00 V Could someone who knows more about this than I do help interpret that? Does that push the likely problem one way or another? Thanks for the help.

Thanks folks - so rockauto is credible, but I think I will leave them as is, and just change them when they start to deteriorate (with Denso Iridiums). The car is 2005 with 85k, so I guess the plugs were last changed at the 6year/60k or 8 year/80k services done by Lexus roughly 7 or 5 years ago (although only 25-30k miles ago).

I've just bought a rather lovely 2005 GS300 SE which has been gorgeously looked after by the couple I bought it from. It's got full Lexus history except for the last 3 services which were done by an independent, and I can't find any evidence of the spark plugs for at least the last 3 years. I'm tempted to change them even though the car seems to be running fine. What's the collective wisdom on this? Worthwhile or waste of money? While I'm at it, the plugs look to be about £20-£25 each - rockauto.com seems to be offering 6 delivered Denso 3473's for £58. Are these guys reputable? There is a note against the plug saying "Part is designed for US, CA Market vehicles" - if it's the same stock number, surely it'll be the same plug as over here? Any advice appreciated!

Thanks for that Brendan - did you fit a flashlube system?

Thanks for all the good advice so far - I guess the message I hear is that, as with any other older car, a thorough inspection is key and then a bit of luck! Mark, your list of problems seems perfectly reasonable to me for a car of this age, if I could get 5 years use on a £5-6k car with maybe £1-2k total on occasional fixes (eg a preventative new rad plus one decently expensive but not terminal problem) over the 5 years (plus servicing) I'd be happy with that. Maybe I'll also have a think about a higher mileage, rather cheaper LS430 and then it's only £3k if it all goes horribly wrong.

Martin - that's a great list, thanks. Sorry to hear of your horror story, that's the sort of thing that does concern me, as I don't fancy scrapping something I've just dropped £6k on.... Mike - thanks, I'm looking forward to the LPG story, although I see you have a 400 rather than a 430, is that a vvti one or earlier?

Hi - newbie lexus fan here. I'm rather smitten with the idea of replacing my aging Avensis with something equally aging but rather smarter, and think I might be settling towards an LS430. I understand the 400 is simpler therefore a bit less likely to go wrong but I do like my toys and the 430 is certainly full of those. Further, even the latest 400s are getting on for 20 years old now and that's old enough to make me nervous - I need my car as transport, not a hobby to tinker with. I do about 10k per year. I've done a fair amount of digging around in the last month or so and seen to have the following as the main things to watch out for: - suspension faults - telescopic steering motors - electrics, particularly subwoofer Is there anything else I've missed? I want to LPG whatever car I get to bring down the running costs - I can find plenty of older models converted, but can't seem to find many 2004/2005/2006s, is there a reason for that? Does the vvti engine run OK on LPG? I know there has been mixed results with my vvti Avensis with valve recession. Finally I spotted what looks like a decent one not too far from me on eBay, there is a decent amount of history and the seller says he'll get lexus Cardiff to change the cam belt and service it before delivery. It looks nice from the pictures. Price seems a little high, but not like the couple I've seen online recently at £8-9k. Does anyone know the seller? Has anyone seen it? Any advice appreciated http://m.ebay.co.uk/itm/Lexus-LS-430-4-3-V8-Saloon-Auto-Tiptronic-/371565070227