84 Secondary Air Injection Pump - Open Circuit

P0418

84 Secondary Air Injection Pump - Open Circuit

Function
To improve emissions and to heat the three-way catalytic converter (TWC) faster, secondary air is blown behind the exhaust valves after the engine is started when cold. For this, an electric pump is used.

Diagnosis conditions
- Engine running
- Battery voltage greater than 7 V

P0418:

NOTE: The triggering wire for the relay of the secondary air injection pump, terminal 85, is monitored.

Wiring Diagram







Diagnosis Procedure










1 Check voltage supply for relay of secondary air injection pump, terminal 86.
1. Remove relay of secondary air injection pump.
2. Connect voltmeter to pin 7 (terminal 86) and ground.
3. Switch on the ignition.

Display: battery voltage

If 0 V is displayed, check DME relay or wire from DME relay, terminal 87, to relay of secondary air injection pump, terminal 86, for continuity.

2 Check relay of secondary air injection pump.
1. Remove relay of secondary air injection pump.
2. Connect ohmmeter to relay terminals 85 and 86.

Display: approx. 70 W at 25 °C

3 Perform adaptation.
1. Switch on the ignition.
2. Wait one minute. Do not press the accelerator.
3. Switch off the ignition for at least 10 seconds.
4. Read out the fault memory.