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Q: Check engine light on, black liquid in the exhaust

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Hello. My car has the check engine light on, that appeared about 10 days ago. Now, there is some black liquid residue in the exhaust. What could cause this? Is it serious? Thank you.

A: Whether or not this is serious would depend...

Whether or not this is serious would depend on the reason the check engine light is on. I would recommend having your vehicle’s trouble codes scanned with an OBD2 scanner by a certified mechanic.

Once the codes have been scanned it will be easier to determine how to proceed with the diagnosis of this issue.

As for the black liquid residue, normally exhaust will release a small amount of water due to condensation inside the engine. When this water mixes with the carbon deposits that naturally build up on your exhaust over time, it can appear to be a black liquid residue. On the other hand, it could also be oil which is a very serious issue that you should have inspected and repaired as soon as possible.

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