Grandland X Engine Control Problems

I understand your frustration. Faulty cable connections to the battery can certainly cause starting problems and trigger engine control malfunctions. Have you checked the voltage reaching the ECU during attempted starts? Also, have you tested the earth connections?

ECU voltage, eh? Good shout. How exactly would I go about testing that? And any specific points I should be grounding to when checking the earth connections?

Precisely. Confirming adequate ECU voltage eliminates power supply issues. As for grounding points, utilize the vehicle chassis near the battery and engine block for reliable earth testing. Given the symptoms and potential connection issues, professional diagnostic services are advisable. It will ensure accurate fault detection and verification of the ECU’s operational integrity.

You were spot on! Turns out it WAS a bad connection on the battery cable; corroded to hell, throwing everything out of whack. Had it cleaned up and replaced the terminal. Cost me 155€ but at least she's purring again. Thanks for the advice!