VSC and VSC off displaying

[mw430]

The VSC and VSC OFF indicators lit up when the car was started a few days ago and stopped when I replaced the petrol cap tightly.

A few days ago the engine warning icon showed followed by the two VSC indicators. They all stay on when the car's driven.

I see there are methods of shorting ODB2 contacts that could overcome this but has anyone cured this problem on a 55 reg SC430?

 

[ColinBarber]

You need to get the error code(s) read to determine the cause of the issue. There are multiple causes for those lights to come on. Resetting the errors without fixing the issue will only result in the lights coming back on again.

[mw430]

Thanks. I thought this might be the case so I ordered an OBD2 reader tonight.

I did try the suggested steps to cancel the errors. That made no difference so I need to find the hard fault to fix it myself.

[The-Acre]

9 hours ago, mw430 said:

Thanks. I thought this might be the case so I ordered an OBD2 reader tonight.

I did try the suggested steps to cancel the errors. That made no difference so I need to find the hard fault to fix it myself.

Keep us posted re the outcome, especially as you have the same engine as us LS430 owners. Always useful to hear of results.👍

[mw430]

The OBD2 code came out as P0031, related to the bank1 O2 sensor1 internal heater current being too low.

I'll get under the car and see if I can check the sensor's got 12V and 0V going to it.

If it has then I'll get a new O2 sensor.

After resetting the code, which was the only one reported, the EML came on quite quickly, followed several seconds later by the two VSC indicators. 

I'll update this when I've checked the voltages.

Thanks for the comments!

 

 

[mw430]

Now I've looked into it I can't even see the sensor and I've read that this is the easier one to get at!

Comparing B2 S1 with this B1 S1, both waveforms go up to just over 0.9V but B1's voltage goes down to a minimum of 0.095V while B2's is above 0.1V.

Does the SC430 take this as a cause of an O2 sensor having a problem or is it the same for other  models?

I guess I can run the engine until it's hot and look at the waveforms again.

If the problem's related to the sensor's internal heater maybe it only shows when it's cold.

Does this relate in any way to the VSC lights and if so how?

What a can of worms!

 

 

 

 

[ColinBarber]

As this is a heater circuit issue there is no point looking at the O2 sensor waveforms, it is on a different circuit and unrelated.

Worth unplugging the sensor and checking the connection for corrosion, possibly even swapping sensors over to see if the fault moves with the sensor or stays with the bank. Typically it will be an issue with the sensor and just needs replacing.

[BachelorDays]

8 hours ago, mw430 said:

 

If the problem's related to the sensor's internal heater maybe it only shows when it's cold.

Does this relate in any way to the VSC lights and if so how?

 

 

 

The o2 sensor has a heater to get it up to operating temp quickly. A check is made at around 5 secs after ignition and an error code registered if the heater circuit isn't responding.

Once the code is registered, since this is the pre cat sensor, default values are used for monitoring the running of the engine instead of actual results from the sensor. So the car will run at less than optimal level.

The VSC errors, as you've noted, can be caused because of a pressure leak in the fuel supply system so are sensitive to the engine running, hence a potential link with the pre cat o2 sensor.

The heater function normally starts to malfunction intermittently first, so the error is also intermittent, or happens only on cold starts. On other occasions the function stops operating suddenly so the error, once registered, remains permanently.

Once you get to it, see if there's anything obviously wrong with the connector and replace to check if the error goes away. But unless it's a broken wire you probably won't get much more out of the sensor.

[mw430]

Thanks guys for pointing out the potential link to the VSC displays and the fact the heater's not on the same circuit as the sensor signals.

I checked out all four sensors. The "failing" pre-cat one has a 0.72V peak waveform while the other has 0.82V. The lowest tester-recorded voltages are close to 0V on all 4. The post-cats are both stable at a middle voltage and both have a recorded 0.82V max. 

Working from a cold start or when the car's up to temperature there's no change in height or speeds of the outputs' waveforms.

If P0031 cuts out the offending sensor and creates an open-loop signal to keep the engine operating is this what the tester is showing, rather than being a low output from an aging sensor which is what I originally thought? I also thought that the lower signal levels could be the result of a low heater voltage but since the levels don't change when the engine's up to temperature that maybe that was wrong too and the thing's just out of spec.

Hopefully I can get the lower panels off this weekend and do a visual cable check and heater resistance check... if I find where its socket is!

 

[ColinBarber]

The heater is just a coil and it is turned either fully on or fully off. It provides heat to the sensor to get to an operating temperature quickly to get more accurate results. The ECU monitors the current it supplies to the heater circuit - if it is out of spec it will throw a heater related error code. Normally it goes open circuit as the heater burns out.

The waveform of the actual sensor has nothing to do with this error, forget 0.72v peak. The heater should get 11v or more, draw less than 2 A and less than 0.25 A.

If there is anything wrong with the actual sensor waveforms you will get P013x or P015x errors.

[mw430]

Now the weather's let me get the car out of the garage I've taken off the centre panel under the engine/exhaust area. The sensor is easily accessible and only recessed by a cm.

The socket's a different matter. Its cable is very short and leads up to a plug in a recess protected by a heat shield. I tried to photograph it but failed due to lack of space.

If I could lift the car a foot off the drive I could look up into the connector area but it's on a jack so I can't. Although it looks straightforward to disconnect I don't want to damage it by following the wrong procedure.

How does the socket release from the plug? Can anyone help me here? 

[ColinBarber]

I think there is a little tab in the middle which you push down which then easily allows the connector to pull away.

[The-Acre]

2 hours ago, mw430 said:

Now the weather's let me get the car out of the garage I've taken off the centre panel under the engine/exhaust area. The sensor is easily accessible and only recessed by a cm.

The socket's a different matter. Its cable is very short and leads up to a plug in a recess protected by a heat shield. I tried to photograph it but failed due to lack of space.

If I could lift the car a foot off the drive I could look up into the connector area but it's on a jack so I can't. Although it looks straightforward to disconnect I don't want to damage it by following the wrong procedure.

How does the socket release from the plug? Can anyone help me here? 

As Colin says, the connection has a piece that needs pressing down to release it, it only goes down slightly.  I assume you also have a slotted socket to remove the sensor?

[mw430]

I know the picture's poor but where is the bit to push, please?

[The-Acre]

I don't know if this will help, it shows how the plug fits on a Denso sensor. It's hard to explain but the plug is only held in with a small clip. On some you press the male plug down, but on some you lift the female plug up.

 

[The-Acre]

Just to add, I'm sure you know that it doesn't disconnect from the actual sensor end!

[mw430]

That's probably the only thing I do know!

The car's connector is secured somehow in the recess and there's something on its far right that never shows in any plug/socket I've seen for this car. I assumed it was the securing mechanism to keep the bits secured to the car so I've never played with it. I don't know if the cable it connects to would be happy being yanked if it was suddenly released.

The area that looks like it may have a locking tab is on the left hand side where the socket is much wider than the plug. That's where I inserted a flat screwdriver blade...and achieved nothing!

Still searching.

[The-Acre]

If your picture is showing the relevant plug then it looks like the clip is at the top, so it looks like you need to push the female part down to release it.  I remember doing it on my GS and I had to push down and pull, both with the same hand!

[BachelorDays]

8 minutes ago, The-Acre said:

If your picture is showing the relevant plug then it looks like the clip is at the top, so it looks like you need to push the female part down to release it.  I remember doing it on my GS and I had to push down and pull, both with the same hand!

You can see it at the very edge of the plug. If it's any help, I'd say it's more a squeeze n pull than a push n pull. Don't try to yank it. Be patient. It'll be stubborn and then just give way.

[mw430]

Something to try Sunday I guess as long as it's not raining.

Thanks both for the hints..

[The-Acre]

1 hour ago, mw430 said:

Something to try Sunday I guess as long as it's not raining.

Thanks both for the hints..

I hope you manage it ok.  If the picture was sharper it would be much easier to see how it fits.

[mw430]

Finally I exchanged the sensor for a Denso and everything's back to normal.

There's a bar on the socket opposite the side that mounts to the car. That locks on a protrusion on the plug that's between two guides. It needed a flat head screwdriver a bit narrower than the width of the bar so that when the screwdriver was turned it forced the bar out and released the plug. I guess anyone that's done an O2 sensor replacement  probably knows this but it was all new to me. I was able to see the plug/socket detail using my Snake Scope, but getting used to the reversed image took an hour!

The heater was open circuit. The new sensor's waveform has the same amplitude as the other bank's forward sensor. Basically all 4 sensors have the same max and min so maybe they could all be good for quite a while longer.

The only noticeable difference in performance with the change was tickover. With the faulty sensor the revs stayed at 1100rpm for a very long time. The new sensor's tickover drops to 800rpm or less in 20 seconds.

Thanks to everyone for their comments and for the sunny weather!