P0410 2004 Chevrolet Trailblazer, What valve or relay should I check first?

Question

Service engine light first came on while running over a series of small washboard bumps on a gravel road. Drained about a teaspoon full of alcohol smelling liquid from lower hose at the pump, erased the code and light stayed off for two trips (over 40 miles total, then light came on again while running over a series of small washboard bumps on a gravel road.

Answer 1

P0410 Secondary air injection system malfunction

One of the condition to set this code is the ingestion of water or debris ingested into he air pump.You can can install a splash shield to prevent this type of condition