GS300 2005 Mk3 'Check VSC' - help to understand Techstream readings

[BristolBrian]

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.

[rich1068]

Would you get the VSC/TRC and orange light for O2 sensors or cat efficiency? When the cats were on the way out on my MK2 GS300 I just got the orange light. And that went out on its own after a few ignition cycles.

[BristolBrian]

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!

[IanA2]

I have a vsc issue too so bookmarking this in case something comes up.

[simonsm]

H II literally joined the LOC about 5 minutes ago, so am delighted to be giving my First offer of a solution so soon!

Whilst I have only just joined, we have had the RX300 for about 4 years, so it's a known entity.

Having had this problem a couple of years ago - a great deal of research on the. American forums lead me to a very simple fix - but it actually works!

More often than not the problem is simply that the fuel filler cap is not seated or tightened sufficiently or the plasticky rubber seal just inside the cap is worn or kinked.

I had not given this another thought, it having worked perfectly, since, until yesterday, whilst on a 200 mile round trip (I work in the NHS so essential travel!) but on the return leg, the VSC and EML lights came on - all else perfect no change in fuel consumption or performance - so eventually pulled over, undid the fuel cap 'massaged'.the seal a bit and refitted - ensuring I tightened it until the clicks started. Within a mile - all warning lights extinguished.

I am sure this solution has been posted a thousand times but hopefully it will be of help to someone.

Best

Simon

 

 

 

 

 

[olumite]

Your exhaust is likely to have a vacuum leak behind the heatshields (just after the secondary cats).

The heatshields retain water and rust the pipework. Removing the heatshields and getting the holes repaired/welded should sort it.

[LexIS200Sport]

5 hours ago, simonsm said:

More often than not the problem is simply that the fuel filler cap is not seated or tightened sufficiently or the plasticky rubber seal just inside the cap is worn or kinked.

What he said. I replaced my fuel filler cap with a brand new one and fixed the check VSC problem once and for all. This was on a 2007 Mk3 GS450h @ ~110k miles.

Several thousand miles later I then had the "Cat efficiency below threshold" error (P0420) and that was fixed by replacing the PCV valve, which was all gunked up, and fixing a leak in the exhaust just ahead of the secondary O2 sensor.

[BristolBrian]

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.

[Lwerewolf]

The only thing that you can interpret are plots of same-side bank o2 readings - the 2nd sensor (downstream of the primary cats) should "lag" and/or be smoother than the first one. You can idle the car and change the fuel injection volume via techstream - it's part of the active tests. Make sure that you've fully warmed the car up beforehand.

The p0420 monitor checks for the "lag" between going from lean to rich and/or vice versa - if you read up on two-way catalytic converters (factory installed on pretty much every single remotely-modern petrol car - notable exception being Mazda's skyactiv-x since HCCI solves the NoX issue), they have an oxygen storage mechanism. By going lean to rich, oxygen is released by the cat for awhile to fuel its oxidation reaction - this causes a delay between the primary (pre-cat) sensor reading rich and the secondary (post-cat) sensor reading rich. When going rich to lean, the cat accumulates oxygen for awhile - leading to the same lag between sensors.

Don't look for a sinewave on the primary o2 while idling - the primary o2 (on all 3GS models) is an air-fuel ratio meter (a.k.a. wideband o2), and the car doesn't (need to) constantly oscillate between lean and rich to maintain a stoich mixture.

At any rate, p0420/p0430 tells you that the ECM has determined that the car's primary cat's oxygen storage capacity has been compromised enough to trip the codes. All sorts of exhaust leaks can cause a p0420 to pop up. A bad primary o2 might also trip it. A bad secondary o2, however, is very unlikely to trip it - they usually go lazy, and a "lazy"/delayed secondary o2 response is... "beneficial" in this case. Winter fuel formulations have also been known to do that... Overall, it's a mess. As for cat degradation - it's actually mostly contamination/poisoning - lead, phosphorus (various substances in the oil, coolant), coatings... Be sure to read up on the topic before you start trying things like acetone in the tank.

Check for exhaust leaks, check that the o2s react properly (i.e. they go rich when rich, lean when lean, primaries don't delay - check with techstream's active test while graphing o2 readouts). If you end up wanting to replace the cat - go for OEM, as aftermarket cats usually have marginal oxygen storage capacity - they've been known to trip the code right from the get-go.

[BristolBrian]

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 !

[Lwerewolf]

p0420/p0430 codes have a threshold - it may look smooth to you (or jagged), but the car might think otherwise. Again, that doesn't really mean that the cat is not doing its job.

I'd test the intake and exhaust system for leaks regardless - might as well do both, since it's standard practice to check pretty much everything that you can on an engine before you replace a cat - you don't want the new cat to fail prematurely due to other problems.

[BristolBrian]

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.

[IanA2]

Would appreciate an idiot guide to how you resolve the VSC issue.

 

Many thanks.

[BristolBrian]

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.

[IanA2]

28 minutes ago, BristolBrian said:

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.

It was, and thanks.

I think I'm ok with sensors & exhaust. 

I've had a look at the Techstream stuff on eBay, they seem to be either very expensive or needs a laptop with a disc drive.

Anmy recommendations on that front from anyone?

Thanks folks.

 

 

 

[BristolBrian]

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.

[IanA2]

11 hours ago, BristolBrian said:

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.

Thanks. I've had a look at the many offerings on eBay. I don't know enough about them, and they most don't give a huge amount of detail, for example whether or not they include a licence key. I'd be very grateful if someone could recomend one that they know will do the joib.

Thanks.

 

ETA: We are a windows free area! Mac and Chromebooks only, I'm guessing most of these widgety things are windows based.

Edited November 24, 2020 by IanA2
xtra info.

[BristolBrian]

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

[IanA2]

7 minutes ago, BristolBrian said:

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

Yup 😞

[cobraBLACK]

If you have a modern Chromebook you can install any Play app, like Torque for example. They can't do everything (no TPMS access for example) but they can read and clear regular fault codes.

[johnatg]

You do of course need an interface device to transmit from OBDII to the Chromebook via Bluetooth. (Not all Chromebooks have Bluetooth).

I have an Autool code reader /interface jobbie to transmit to Torque on my Android phone. Only covers engine codes, but does so quite well (also provides real time live data) and a lot less hassle than setting up the laptop and cable for Techstream. Works on all my cars with OBDII, too!

And the whole thing cost less than £10 (excluding the phone!)

[IanA2]

Very helpful, many thanks.

I have an decent Acer CB and have installed Torque.

Just need to find out which widgety thing to buy. Afraid I'm still at sea on that front.....

[johnatg]

Mine looks like this but it's not quite that model. I've had it for several years.

https://www.amazon.co.uk/AUTOOL-Scanner-Adapter-NEWEST）-Diagnostic/dp/B07P2HKC4Y/ref=sr_1_7?crid=2JMEC4467GRTJ&dchild=1&keywords=autool+obd2&qid=1606219647&sprefix=autool%2Caps%2C457&sr=8-7

[IanA2]

9 minutes ago, johnatg said:

You do of course need an interface device to transmit from OBDII to the Chromebook via Bluetooth. (Not all Chromebooks have Bluetooth).

I have an Autool code reader /interface jobbie to transmit to Torque on my Android phone. Only covers engine codes, but does so quite well (also provides real time live data) and a lot less hassle than setting up the laptop and cable for Techstream. Works on all my cars with OBDII, too!

And the whole thing cost less than £10 (excluding the phone!)

Thanks, I have looked at the Autool CS320 which as you say works independently. I don't have an Android phone at the moment, but my Acer has Bluetooth, so maybe that would work?

[IanA2]

14 minutes ago, johnatg said:

Mine looks like this but it's not quite that model. I've had it for several years.

https://www.amazon.co.uk/AUTOOL-Scanner-Adapter-NEWEST）-Diagnostic/dp/B07P2HKC4Y/ref=sr_1_7?crid=2JMEC4467GRTJ&dchild=1&keywords=autool+obd2&qid=1606219647&sprefix=autool%2Caps%2C457&sr=8-7

Thanks, that looks like a possible and straight forward solution. Fingers crossed.