What was once an occurrence every 2 or 3 months now appears to be every 2 or 3 days.

When driving along undulating country roads, my '15 L405 SDV8 is starting to go into limp with the red triangle. It always seems to be after a period of going downhill where the engine is either idling, or at low revs providing a slight bit of engine braking.

The only fault I'm seeing on the iiDTool is an issue about injector 4 data being incomprehensible. However, this error code seems to be there all the time and the milage trigger doesn't match the time restricted performance comes on.

When not in limp, car drives fine and there's no visible smoke or performance issues.

Clearing the faults on the iiDTool takes it out of limp. It's odd that it doesn't seem to pick up what's triggering the limp though? Any ideas? It has come on about 10 times now and is always when I'm going downhill

Hi,

I am not sure if my issue relates to yours but I would get the same fault but it never showed up on any diagnosis with LR. It was essentially a ghost problem.

My issue on 2015 SDV8.
Restricted performance, limited power. Can happen any time, but mainly when cold on start up over a period of 3 years at intervals of 3-4 months.
My fix was to turn the car off, open bonnet, shake wiring looms near both air intake boxes and follow wiring up to the manifold area and keep checking all wiring connections. Problem would go away for a few months.
Problem did not occur for nearly 14 months until 3 months ago where out of nowhere it happen 3 times over a 1 month.

Car was in LR for a service and car stopped on the mechanic when he was driving. Came back with Restricted performance. He diagnosed it as a fuel sensor in the intake manifold area associated also with the wiring loom. I told him to shake the wiring looms around and the fault went away. Ordered new wiring loom for the specific fuel sensor and a new fuel sensor. Total repair is quoted at 345AUD. Car is in next week for the repair. I will get the part numbers and specific details after I get the receipt. Will report back.
Cheers

I should add that the last time the restricted performance issue happened was rolling down a hill the engine just turned off. I tried my remedy 3 times on the side of the road but it did not work. Drove home turned the car off came back 10 minutes later and tried my fix of shaking the looms and I not had the issue since 4 weeks ago.