Blazer LT 4wd 4.3 6cyl with 127k miles. The CEL came on 10/15/11 and 8/22/12, both times it was raining. I cleared the CEL by disconnecting the battery both times and did not have the codes read. This time the CEL came on 2 days after Hurricane Sandy and I decided to have the code read at Advance Auto.
It was a PO410 Secondary Air Injection System. The counter guy thought it was the EGR valve. The EGR valve is easy to get to on the Blazer, so I figured it wouldn’t hurt to pull the valve and clean the passages this weekend.
I did a little research and the code actually refers to the Secondary Air Injection System (AIR pump). Blazers have an issue with water acclimating in the pump housing and freezing up the pump, there is a TSB for it. http://acdelcotechconnect.com/pdf/tsb/tsb_04D-183.pdf
I have to put the Blazer up on ramps and remove the skid plate to get to the pump. I’ll check the fuse first, but is there anything else I can do to verify the pump’s operation before getting under the truck?
Note, the CEL does not come on until the Blazer is fully warmed up (+15 min driving). If the pump is not working, wouldn’t the CEL light immediately? The distributor cap and rotor was replaced in Sept at 125.5k miles. The truck runs and drives fine with or without the CEL on.
Any suggestions or thoughts would be appreciated.