What is secondary air and what is an AIR pump?
Secondary air is known as an air injection reaction system (AIR). It’s designed to reduce emissions during cold startup. The system consist of an air pump (like a small compressor) a one way valve, and a solenoid valve.
The purpose of this pump is to inject air directly into the exhaust manifold during a cold start to complete the combustion process. At cold startup, the computer commands a rich mixture. The extra air from the AIR pump helps oxidize the extra hydrocarbons and carbon monoxide in the exhaust during this rich mixture period. The AIR pump is active only during the first 20-120 seconds of engine operation, or until the catalytic converter heats up.If the AIR system doesn’t work properly, all that extra fuel from a rich startup could cause the catalytic converter to overheat once it reaches operating temperature.
The PCM monitors the effectiveness of the AIR pump by watching the O2 sensor. So you start the cold engine. The PCM sees it’s cold by checking the engine coolant temp sensor. If it’s below 195°, it’s “cold.” The PCM commands a rich mixture. The PCM power the AIR pump relay to switch power to the pump (electric pump draws high current, so it needs a relay to switch the power). Extra air blows into the exhaust and PCM starts a timer. If the O2 sensor doesn’t show a lean condition within the time limit, it figures the pump isn’t working and sets a P0411 secondary air injection system flow (low flow or no flow) malfunction. The PCM activates the AIR relay by providing ground to the control coil. The PCM checks for faults on the control coil side of the AIR relay, and sets a P0412 secondary AIR circuit malfunction if it finds one. The problem can be an open in the wire from the relay to the PCM, no power into the control coil from fuse 128, or an internal “driver” fault within the PCM that won’t provide ground to the relay control coil.
Once the AIR relay is activated, the PCM checks voltage on the power feed to the AIR pump. If it detects a problem on the secondary side of the relay, it sets one of two codes; a P1413 secondary air injection system monitor circuit low, or P1414 secondary air injection system monitor circuit high.
©, 2015 Rick MuscoplatPosted on by Rick Muscoplat