What happened to the black ash in the exhaust pipe after Honda crv cleaned the throttle?

Caused by incomplete combustion of gasoline.

It is caused by adding inferior gasoline or fuel label mismatch. The normal blackening of the exhaust pipe is generally related to factors such as direct injection in the cylinder, turbocharging, long idle hot car time, poor air quality, etc., because these factors all affect the combustion of the mixture to a greater or lesser extent. If inferior gasoline, engine oil and three-way catalytic failure are used.

These will aggravate the symptoms of black exhaust pipe.