Topic

Have a 2001 MGF CVT, is fine when first driven but when it gets warm and I brake the box goes down the gears quickly and almost throws me through the screen. Also after stopping it appears to drive off in top gear then goes down to a low gear as I press on the accelerator.
Pscan reports and historic error code of P0500 which I cannot delete. No warning lights on the dashboard and speedo and rev counter function correctly.
There are 2 speed sensors on the CVT gearbox? Gearbox oil was replaced and still same issues. Have also replace the throttle sensor and same again no difference.
Is there anything that should show up in Pscan and apart from cleaning contacts etc it is worth replacing th speed sensors?

Regards

Dave W

CVTs are not something I have really looked at in any detail, but a quick scan through the workshop manual does largely suggest a speed sensor issue which prevents the correct ratio changes based on input and output speed sensing.

I'm not sure if pscan has access to any data beyond the fault codes reported back from the gearbox controller https://pscan.uk/features/mgf.html so for more detailed information it might have to be a T4 testbook direct read from the gearbox controller...?? Hopefully someone will be along shortly with more info on that.

I can't find any literature on testing the sensors, and looking at Rimmer's prices, you probably don't want to buy one if you don't need to!

So, prior to shelling out I would suggest carefully tracing the wiring harness for both sensors and checking for breaks, shorts and dodgy connections. If that doesn't turn up anything obvious a speed sensor from a scrap vehicle may at least confirm the fault at a more sensible price.

Sorry I can't offer much more help.

Hi and welcome to the forum Dave

Have a look at https://www.the-t-bar.com/forum/pscan-uk-diagnostic-tool-forum/96704-software-version-0424#190622

Let us know how you get on.

James

Ok have downloaded the latest software for Pscan, still reports P0500 which I cannot clear.
Am in Perth Australia so not sure of many donor cars being around.
Whilst playing with Pscan I did note that it reports engine revs at over 1500 when live scan the power steering unit, but when I look in engine mode it reports the correct value of around 800.
Weather not looking to great this weekend, well it is winter here so might have to wait to have a look at the sensors.

Does the engine speed actual go to 1500 rpm when looking at the steering or is that just what the scanner reports?

Thanks,

The engine revs are around the 800 but it reports 1500 but only when I look in the power steering section. That’s why it caught my eye.

David

I dunno about Perth but there are some places here in Melbourne that might have what you need:

https://www.linkautomotive.com.au/

https://www.allford.com.au/

If you have any problems with them sending to WA, I could probably organise freight cheap on your behalf.

Many thanks for that will have a look at the sensors in the coming weeks and then see where we go from there. I did buy it knowing there was a gearbox issue, but the fact it had a new head gasket swung it for me as I do believe it is a sensor related issue.

Dave

Ok a quick update, cleaned all connections and still same issue. Did notice that the (main) speed sensor was loose and I can turn it around as though it has a screw thread. So my question is, should it be doing this?

Regards

Dave

Just a quick update, have replaced the speed sensor, still same issue so have on order the gearbox speed sensor. Now have suspension sag on drivers side, so will try to re gas snd see if that works.

Well weather is good and a weeks holiday, so I have finally replaced the gearbox speed sensor this morning. Guess what, still the same issue. Have the same historic fault code that won't clear P0500. I must admit that the problem doesn't seem as bad anymore but is still there, jumping from 6th to 2nd when slowing down.