Engine Light ON (or Service Engine Soon Warning Light),Engine hesitation
P0411 GMC Possible Causes
Vacuum hoses damaged or pinched,Faulty Air Pump inoperative,Faulty Air Pump harness is open or shorted,Faulty Air Pump circuit poor electrical connection
P0411 GMC Description
The Secondary Air Injection (AIR) System aids in the reduction of hydrocarbon exhaust emissions during a cold start-up. This occurs when the start-up engine coolant temperature (ECT) is between 5-50?? (41-122??), and the intake air temperature (IAT) is between 5-60?? (41-140??). The AIR pump operates 5-60 seconds after start-up. The powertrain control module (PCM) activates the AIR system by simultaneously supplying grounds to the AIR pump and the AIR valve relays. This action closes the relays’ internal contacts. The AIR pump and the AIR control solenoid valve/pressure sensor assembly are in turn energized, the pump runs and the control/shut-off valve opens. The AIR pump sends pressurized fresh air into the pipes/hoses through the open control/shut-off valve, and into the exhaust manifold. The extra air accelerates the catalyst operation, helping it to reach operating temperature faster. The AIR pump remains ON for a short period of time after the control/shut-off valve is commanded OFF. When the AIR pump is commanded OFF it will not run or be activated until the next vehicle start. When the AIR system is inactive, the closed AIR control/shut-off valve prevents air/exhaust flow in either direction. The AIR system pressure sensor is used to monitor pressure at the AIR control solenoid valve/pressure sensor assembly inlet during the commanded ON/OFF states.
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