Intermittent check VSC / AWD warning, only at motorway speed

Lexguy64 · October 28, 2023

Sorry if already covered before, just looking for advice with the check VSC and AWD warnings which have started occurring intermittently but only whilst driving on the motorway. The warnings have occurred each time I have driven on the motorway, approx once a week for the past month, but the warnings only stay on for around 5 minutes and then disappear until the next time driving at speed.

No issues at all when in normal town driving. Also when the warnings do appear I cannot feel anything suggesting loss of power to any of the wheels or the ABS kicking in suggesting the ABS sensor?

I know that the auxiliary Battery is often suggested as the cause, but I have no issues starting, also with this occurring when the Battery would be charging with driving I do not think this is the cause, unless you think otherwise.

any ideas??

katabrontes · October 28, 2023

Check the tyre pressures. I have a similar problem with these lights coming on at odd times. It was suggested that it could be due to imbalance in the wheel sensors. Could be a bit of dirt or if the pressures are adrift then one wheel will turn slightly faster and might cause it. Never found the cause of mine although it happens much less since I replaced the HID main beam bulbs with LEDs which suggested it might have been a CANBUS issue. No fault codes ever appear.

Lexguy64 · October 29, 2023

Thanks for the suggestion Michael, to be honest I haven’t checked the tyre pressures for a while but they are all still at the right pressures so that is not the problem for me.

katabrontes · October 29, 2023

Hi David, mine is still a mystery but it is less often since I changed the main beams to LED even though the HID conversion was stated to be CANBUS compliant. I don't worry about it any more. It always clears if I stop the engine and restart it. Never failed an MoT as my garage knows the stop start trick so if it happens they can clear it.

RONNIE W HODGEKINSON · October 30, 2023

On 10/28/2023 at 7:53 PM, Lexguy64 said:

Sorry if already covered before, just looking for advice with the check VSC and AWD warnings which have started occurring intermittently but only whilst driving on the motorway. The warnings have occurred each time I have driven on the motorway, approx once a week for the past month, but the warnings only stay on for around 5 minutes and then disappear until the next time driving at speed.

No issues at all when in normal town driving. Also when the warnings do appear I cannot feel anything suggesting loss of power to any of the wheels or the ABS kicking in suggesting the ABS sensor?

I know that the auxiliary battery is often suggested as the cause, but I have no issues starting, also with this occurring when the battery would be charging with driving I do not think this is the cause, unless you think otherwise.

any ideas??

I would get the 12V Battery checked Seems to me a Likely Cause But Of Course it could be a Faulty sensor or even something else...Lots of these little problems in my opinion seem to Eminate from the Battery......

Greisingel · October 30, 2023

Get Techstream on to it to see if any errors are stored.

Lexguy64 · October 30, 2023

I would but don’t have access to techstream. How do you guys do this without having to go to the dealer?

katabrontes · October 30, 2023

My local garage checked mine with Techstream and I did it with a small dongle. No error codes showed up.

Greisingel · October 31, 2023

This is true no error codes if no accompanying MIL/CEL (the yellow engine icon)...hence stored

get a full wheel alignment and maybe consider 4 new tyres. Possibly steering spring lock?

katabrontes · October 31, 2023

Might be worth a try but I did this about a year ago and it made no difference.

Lexguy64 · November 1, 2023

Thanks all for the suggestions, however I’m not sure whether this would answer why it is only at speed on the motorway that the errors flash up. Surely if it is the Battery or tyres (approx 40% worn) or alignment, then the problem would appear at other times.

katabrontes · November 1, 2023

Mine is very intermittent and quite unpredictable. It used to happen a bit more often in the rain but not consistently. So far it has defied diagnosis but I have stopped bothering about it as it doesn't seem to affect the braking and always resets when the engine is restarted. Sometimes it just goes off on its own. Best suggestion was that it was a glitch in the main 'computer' which resets every time the car is started which is why it clears. Don't lose sleep over it and learn to live with it. It could otherwise be a very expensive fix for precious little benefit.

Lexguy64 · November 2, 2023

I would agree, no point worrying if it is not causing a problem and the car always starts without problem. As you say it could be an expensive fix for no benefit given the age/value of the car anyway.

Will be keeping up with the basic servicing/consumables etc but leave the expensive repairs unless I have no choice.

katabrontes · November 2, 2023

Maybe worth using a small local garage to do your MoT so you can explain how to clear the problem if it happens during the test. Big boys are probably less flexible. As it doesn't affect any safety critical features it shouldn't be a fail issue but some people always take too precautionary a position.

Greisingel · November 5, 2023

It's a pain. I get an intermittent P0430 MIL (O2 sensor). It is an electrical milliamp fluctuation. I just turn it off with a cheapo OBD fixer. I replaced the sensor with a state of the art Denso one.

But these older cars may just throw some momentary electrical intolerance that in fact is not caused by the vehicle mechanism it is monitoring.

It may be that at speed this fluctuation is more likely....for whatever unknown reason. These are aging cars we own.

You could try hooking up an OBD recorder at the beginning of a longer, faster (ie motorway) journey to see if anything records. Certainly in TIS you'd possibly see a stored code to give a clue.

ColinBarber · November 5, 2023

10 hours ago, Greisingel said:

I get an intermittent P0430 MIL (O2 sensor). It is an electrical milliamp fluctuation.

The wiring and circuit is designed to ignore any interference. For P0430, the ECU only performs testing periodically and needs two positive reading before it will trigger an error - it's a tried and tested system that is still used on cars being built today. P0430 has nothing to do with the sensor, the sensor is working fine, that's how it detected a problem. Normally this is an intermittent fault at first, as you are one the limit of what is acceptable or not, and results vary with driving conditions, but will eventually becomes more frequent and/or permanent. The only flaw is that whilst the system is testing for the Cat not working correctly, it is more often a lazy upstream Air/Fuel ratio sensor running your engine a little rich or a small air leak in the exhaust that causes to error, rather than the Cat itself (but the Cat certainly can also be on it's way out).

Greisingel · November 6, 2023

On 11/5/2023 at 11:13 AM, ColinBarber said:

The wiring and circuit is designed to ignore any interference. For P0430, the ECU only performs testing periodically and needs two positive reading before it will trigger an error - it's a tried and tested system that is still used on cars being built today. P0430 has nothing to do with the sensor, the sensor is working fine, that's how it detected a problem. Normally this is an intermittent fault at first, as you are one the limit of what is acceptable or not, and results vary with driving conditions, but will eventually becomes more frequent and/or permanent. The only flaw is that whilst the system is testing for the Cat not working correctly, it is more often a lazy upstream Air/Fuel ratio sensor running your engine a little rich or a small air leak in the exhaust that causes to error, rather than the Cat itself (but the Cat certainly can also be on it's way out).

Makes sense. But......

It has been steady at average of 240 miles between triggers over the last 3 years – consistently. Is more prone in wet weather. Eg 1,000 miles in summer motorway driving – nothing. Wet = 80–120miles trigger. This is why I felt it was something outside the CC performance.

".......it is more often a lazy upstream Air/Fuel ratio sensor running your engine a little rich or a small air leak in the exhaust that causes to error, rather than the Cat itself (but the Cat certainly can also be on it's way out)" This is to me is likely the issue.

Useful thinking, thanks