Limp mode

[bri]

Fiat ducato 2019 ,l have been caught out quite a few times now and I'm concerned about the cause.driving on motorway and suddenly the vehicle descelerates.at this point l pulled over on the hard shoulder and turned off the engine only for a couple of minutes,at Which point l started the engine again and all was well.this has happened several times now.the as said l had a faulty battery,which l changed for a new one.on another occasion l was advised to take it for a diagnostic,which proved to be clear.thinking l was over the problem until the other day when same happened again.can anyone help please? Has anyone else had similar issues

 

[the1andonly]

Assuming that the correct sort of ODBII tester was used and it didn't show a fault then I'd start by fitting a second earth strap between engine and chassis. Even if it had shown a fault code, you have to be careful with ODBII codes. They might point you in the right direction but not necessarily the right component which can get expensive - so try the cheapest options first.
One possibility that hasn't been mentioned yet is the rheostat on the accelerator pedal. The carbon track cracks and gives intermittent faults including limp mode.

Youre absolutly right about obd2 error codes being ponters to the direction of the problem ie what country we are in. Multiecuscan is a fully functional fiat compatable scanner and can fully test /monitor alsorts including the pedal sensors (2 of them) heres an example, forgive the choice of colours difference not obvious.

 

[RV72 SAM 🏴]

On the newer 9 speed auto, if you apply the brakes at the same time you have the accelorator depressed it goes into limp/no acceleration/need to stop. As soon as the vehicle comes to rest all is well.

Found by testing brakes after a bit of a puddle.

So any chance of a dodgy brake switch or a bit of left foot braking?

Used do that in the old days dry brakes out quick so they stop when required manwells mainly, not many autoplatics around then. It wouldn't occur to me do it that way on the moho though . . .

 

[RandallC]

Was a big puddle, maybe a bit of a flood... AND being of a certain age when drum brakes were all round yep still dry them out after a puddle or very wet run.