Operating principle
On cold start (coolant temperature: +15...+35°С) the secondary air supply system supplies air behind the exhaust valves for 65 seconds. As a result, the exhaust gas is enriched with oxygen, post-combustion takes place and thus the catalyst warm-up phase is shortened. The control is carried out by the Motronic control unit J220 via the secondary air pump relay J299 to the secondary air inlet valve N112, (bypass valve) and combination valve. In addition, after each subsequent start of the engine (at engine temperature up to 85°C) the secondary air supply system is switched on with a delay of approximately 20 s for 5 s at idle and is tested by the self-diagnostic system.
Secondary air pump relay J299
NOTE: The secondary air pump relay J2991 is plugged into slot A4. If an auxiliary tool is needed to remove the relay or control units from the relay block, then first disconnect the ground wire from the battery.
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