Air injection, function - GF14.30-P-3012CY

ENGINES 272.911 in MODEL 204.0 up to Model Year 08/AEJ 07 

ENGINES 272.921 in MODEL 204.0/2 up to Model Year 08/AEJ 07 

ENGINES 272.947 in MODEL 204.0/2 up to Model Year 08/AEJ 07 

ENGINES 272.948 in MODEL 204.0 up to Model Year 08/AEJ 07 

ENGINES 272.961 in MODEL 204.0/2 up to Model Year 08/AEJ 07 

ENGINES 272.971 in MODEL 204.0 up to Model Year 08/AEJ 07 

The air injection more rapidly warms up the catalytic converters to operating temperature after starting and thus improves the exhaust emission values in the warming-up phase.

The injected air is delivered by the electric air pump (M33), which is actuated through the secondary air injection relay (N10/1kP).

For air injection, the air pump switchover valve (Y32) and the electric air pump are actuated at the same time by the ME-SFI control unit (N3/10) for up to 40 s after engine start, when:

• Coolant temperature >-10°C and <35°C
• Coolant temperature >+7 °C and <35 °C (for code 494 USA version)
• Engine speed < 2500 rpm
• Throttle valve is not fully open (no full-load range)

Following actuation, air injection remains locked. Renewed enable of air injection will only take place if the firewall catalytic convertors cool down again due to a sufficiently long stoppage time of the engine. The electrical air pump also has sufficient time to cool down again.

If the air pump switchover valve is actuated at the ground end by the ME-SFI [ME] control unit, it connects the vacuum from the variable intake manifold to the air shutoff valves. These valves open and the injected air from the electric air pump is injected into the exhaust ports of the cylinder heads.

Functional principle 

The injected air reacts with the hot gases in the exhaust ports and in the firewall catalytic converter. Oxidation of carbon monoxide (CO) and hydrocarbons (HC) takes place (afterburning).

This afterburning leads to an additional increase of exhaust gas temperature (exothermic reaction), which also warms up the catalytic converters.

Diagnosis

Air injection can be released for diagnosis using DAS for a max. of 2 minutes (for a warm engine even shorter).

Prior to the next actuation, it is essential to maintain a cooling time of 30 minutes, otherwise the electric air pump may be damaged (overheated).

	Electrical function schematic for secondary air injection		PE14.30-P-2050-99FAB
	Component description for coolant temperature sensor	B11/4	GF07.04-P-6043CY
	Crankshaft Hall sensor component description	B70	GF07.04-P-6221CY
	ME-SFI [ME] control unit, component description	N3/10	GF07.61-P-6000CY
	Component description for the electric air pump	M33	GF14.30-P-2000CY
	Component description of air pump switchover valve	Y32	GF14.30-P-2020CY
	Component description of aspirator shutoff valve with integral check valve	126/1, 126/2	GF14.30-P-2100CY
	Component description for the throttle valve actuator	M16/6	GF30.20-P-2021CY
	Three-way catalytic converter, component description	157	GF49.10-P-2010CY