P38A "gearbox fault" with quick on/off throttle

P38 - 2.5 DSE

If im accelerating quite hard but do a quick on/off of the accelerator the gearbox occasionally goes into fault and it wont go into 1st until i turn the engine off and back on again.

Its only occasionally and during a specific set of parameters, but its bloody irritating when it does happen. (tends to be on this one roundabout on the way to work!)

Impending doom or just one of those things?

Could be a sticky valve in the block.....

Not sure on the 4HP22 box, but in the 5HP24 are two speed sensors, one on the engine input side and one on the output side....if it detects a differential in speed that the box isn't mapped for, it will throw a fault thinking that something in the box is slipping excessively or broken!

Maybe the quick on/off of the throttle causes momentary slip in the box and the ECU goes into safe mode.....

There is a sensor on the gearbox at the back where the connector has snapped off. Ive ignored it as generally it behaves itself. *wishful thinking*

Perhaps this is one of the sensors? Ill have to get a picture to identify it (I cant remember exactly where it is)

Has happened to me once in my 2.5 DSE, when accelerating quickly to overtake, vehicle then stays in a high gear until you stop and switch ignition off. I imagine it clearing itself on an engine restart indicates a 'soft' fault.

I should probably change the oil and put some of that lucas stuff in it, no idea if its ever been changed.

SpanishTony said:

Has happened to me once in my 2.5 DSE, when accelerating quickly to overtake, vehicle then stays in a high gear until you stop and switch ignition off. I imagine it clearing itself on an engine restart indicates a 'soft' fault.

Click to expand...

Yeah thats the one. It always does it at the worst possible moment haha!