I have a 2014 ford focus se and my check engine light keeps coming on and off. When I brought it my mechanic told me it could be a head gasket. But when I did the odometer test it told me oxygen sensor. So should I do a block test?
Since you're seeing a check engine light that means there are codes stored. Codes tell you that a condition exists which usually can have multiple causes. There won't be a code for a blown head gasket if that's what you have. What are the conditions that led your mechanic to believe you have a blown head gasket? Are you losing coolant? Is there coolant in the oil or vice versa? What are the actual codes?
You should do a complete diagnostic scan for codes and data. If a blown head gasket is suspected you can get a test kit for that, but it won't necessarily trigger on every possible way the gasket can leak.
