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Hello, got the usual F display, P1840 via star, goes into limp mode.

I’ve been here before with this car.

Last time the gearbox 1st gear hub snapped, rebuilt the gearbox, after sending the transmission ecu to ecu testing, they said no fault found (which I can confirm as it was mechanical).

I rebuilt the box and placed the ecu back in (the original) as it was tested as being ok.

No forward drive although D displayed and no faults, reverse fine.

I put a whole secondhand box in for £150, all fixed in the end.

Now fast forward four years, p1840 fault code.

I thought i know, will swap the ecu for the ecu testing ok one.

Swapped it all out, guess what? No forward drive. Did work with old ecu in limp.

So I am thinking the ecu was faulty and my box rebuild was fine four years ago.

So I am reluctant to send my ecu to these guys as they returned it saying no fault found but clearly it is faulty.

I assume only the A170 ecu will work? I can’t put in one from a A160?

By the time i pay ecu testing £212 I can buy a whole a class for £250.

If ecu’s swap then maybe worth a try but I’m thinking of petrol torque curve being different so gear change times different.



2 Posts
Take the chip board out of the Gear selector lever and clean the inferred sensors, often they get grubby and dont receive the signals strong enough. Giving a F warning. Same as a battery thats not upto scratch.
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