Our battery not charging light went on. Replaced alternator (cdn tire), light still on. Got it checked: battery and alternator working properly. Drove: light went off but engine light went on, then gauge lights went off, car drove like in low gear, only 5 km/hr max. Next day, could not charge.
mechanics said we need new ecu but can't guarantee it. 1200 dollars. Should we go that route?
If the alternator is charging correctly, the ECU could be faulty. Ensure the alternator has sufficient ground connection before you proceed with replacing the ECU and ensure the wires are not broken in any of them.
You can get a used ECU for a much lower price than that and either way you need to reprogram the ECU before you can use it.