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.
Between the air pump and the exhaust manifold, there is a reed valve that is supposed to keep water created from the combustion process from getting into the pump. If water gets into the pump, it is only problem
First step is to check the motor. You could unplug it and check for continuity across the terminals. If that is OK, then make sure that the path for the air is not restricted. Should be no problem tot he reed valve, but the reed valve itself could be carboned up or the pipe between the manifold and the reed pipe clogged.
If these are clear, then look at the passage(s) molded into the manifold between the pipe and the exhaust stream. Chances are that this last leg is clogged up. You can clean it out with a spray carburetor cleaner.
Thanks Keith, I’m hoping to get underneath and have a look this weekend. I have to remove a skid plate to get to the pump so hopefully it won’t be too corroded. I’ll also clean the throttle body and the EGR valve while I’m at it. I broke down and ordered a code reader but probably won’t get it till next week.
11/4/12
I replaced two rotten vacuum lines at the pump. Didn’t clear the code though. The pump may be running at start up. Some of the hose are crimped and some are clamped, it probably has to go up on a lift to get proper access to the pump and hoses.
Once I get the code reader I’ll take another look at it. I still have to clean the EGR valve and then run some Sea Foam through the PCV hose.
I have until Feb 2013 before the next NJ Emissions Inspection.