P38 - Help! Now constant random kickdowns

Hi Guys.

As per my previous thread, we're on holiday in Lanarkshire and the gearbox has been randomly kicking down. Not used it for a couple of days but today it started doing it almost constantly making it almost undrivable.

Someone suggested the throttle position sensor in the previous thread. Is there any testing I can do without a multimeter?

Failing that, any other suggestions would be welcomed.

Anyone recommend any P38 experts in this area? We're just outside Biggar. Otherwise the ride home will have to be courtesy of the AA!

Guy

See if it still does it if you run in 3rd gear.

Datatek said:

See if it still does it if you run in 3rd gear.

Click to expand...

Hi Datatek.

Yep tried that. Still does it.

Gonna try and get under it in a bit to check any electrical connections I can find.

Guy.

Hi All.

Well we managed to get back from Scotland. The Rangie started randomly changing down for about the first 20 miles and then behaved itself the rest of the way home, although it did seem a bit sluggish.

Went out in it today and it started doing it pretty much constantly - at a constant speed, it would suddenly change down one and sometimes two gears. After a while it stopped doing it.

Looked at Rave, and apparently if the tps goes duff then it inhibits kickdown completely so I'm not so sure of that now. Anyone have an opinion on that?

I really need to get this sorted quickly. Any more thoughts anyone?

Guy

Ok, had my fault codes read and the gearbox is reporting
'Throttle Angle is Incorrect'
and
'Fault on solenoid valve 1'

The TPS seemed to be showing flat spots when he looked at the live data from it as the values were jumping up in big steps when the accelerator pedal was pressed, although he seemed to think this could be dodgy wiring - I'm not convinced about that. Strangely though, a TPS fault is supposed to inhibit kickdowns but that still works. Autologic reported that this would cause erratic gearchanges though, which is definitely what I'm getting.

RAVE states that 'the closed throttle voltage needs to be reset' if the TPS is replaced. Is this something I can do myself or does it need another Autologic/testbook session?

Should I be worried about the solenoid valve fault? I couldn't see what the symptoms of this would be.

Appreciate any thoughts on the subject.

Guy

I too have suffered the same problem but, thanks entirely to Kooky Guy's help and advice, I've managed to cure it, the "Gearbox Fault" message no longer appears on the dash and the rangie no longer randomly down-shifts.

In our cases the fault was caused by water/oil ingress in a connector, in the cable running from the intake to the gearbox (the connector is found between the passenger side cylinder head and the bulkhead). A quick clean and a good soaking with WD40 cured the problem. I've also loosely cable-tied the cable to one of the air-conditioning pipes, to try and avoid this happening again.

Hope this may help anyone else suffering this problem and perhaps save a trip to a dealer.