On the way home the other day, the SERVICE ENGINE SOON light came on. When I got home I pulled codes and got a PCM P0410 code that decodes to SECONDARY AIR INJECTION SYSTEM fault. Following the link to the troubleshooting section, I found that the most likely cause is a blown fuse in the Air Pump circuit, most likely caused by the pump seizing up from frozen water in the pump, or corrosion from water getting into the pump.
So my question is, what is the computer actually testing to arrive at the conclusion that there is a fault. Does it only sense voltage going to the pump, or does it sense that the pump is not actually running? I hate to just go ahead and replace the pump if there could be some other malfunction. Also, the troubleshooting guide stated that the water in the pump is probably due to leaking check valves in the air circuit, allowing exhaust gas and moisture back into the pump. Therefore, the check valves should be replaced along with the pump. Does anyone have any idea about how big a job this is?
Thanx in advance.