chalkie

Hi there, I have an 2016 registered Astra Tech, and since the day after I brought it I've been having issues with it going into limp mode, the OBD reads it as P2128 and P2138 throttle voltage error. A garage replaced the throttle and sensor but the issue persists. I've tried everything and I'm at my e end, no garage seems to be able tofix the issue and as I've brought it on finance the Company are saying I have to repair it. Any advice on what it could be? Thanks in advance.