check engine light upon accelerating, flashes, now stays on..power lacking? on 2000 Volvo S40

timing belt was allegedly changed recently as well as the sprocket and water pump .. also, i took it to get the code read to one place and they said the ODB2 connection does NOT work?!! meanwhile the place I got it from just did an inspection which I thought there was no way around when the machine needs to plug in directly.

Asked by for the 2000 Volvo S40