Secondary Air Injection System

Secondary Air Injection System

=> [ Combination Valve for Secondary Air Injection, Checking Function and Proper Seal ] Combination Valve For Secondary Air Injection, Checking Function and Proper Seal

=> [ Secondary Air Injection Solenoid Valve, Checking ]

=> [ Secondary Air Injection Pump Relay, Checking ]

=> [ Secondary Air Injection Pump Motor, Checking ]

Principle

Due to the rich mixture during the cold start phase, the exhaust emissions contain an increased level of unburned hydrocarbons. The Secondary Air Injection (AIR) system improves the secondary oxidation within the catalytic converter, thereby reducing harmful emissions. The heat released by secondary oxidation shortens the start-up time of the catalytic converter considerably, as well as significantly improves emissions quality during the cold-running phase.

Function

• During cold start (with coolant temperatures +15 to +35° C), the Secondary Air Injection (AIR) system blows air behind the exhaust valve for approx. 65 seconds. This produces an oxygen rich exhaust gas, causes the after burning and reduces the heating-up phase of the catalytic converter.

• In addition, the Secondary Air Injection (AIR) system is switched on with a delay of approx. 20 seconds during idle for 5 seconds after every subsequent engine start up to max. 80° C coolant temperature and is checked via On Board Diagnostic (OBD).

Combination Valve for Secondary Air Injection, Checking Function and Proper Seal

The following procedure is used to test all combination valves.

Special tools, testers and auxiliary items required

• Hand vacuum pump (V.A.G 1390)

Test conditions

• Vacuum lines and hose connections free of leaks.

• Vacuum lines not plugged.

Test sequence

- Remove the vacuum hose from the combination valve.

- Connect hand vacuum pump (V.A.G 1390) to combination valve vacuum connection.

- Remove the air duct hose - arrow - from the Throttle Valve Control Module (J338) and position aside.

- Disconnect the Secondary Air Injection hose - arrow -.

- Inject a light air pressure into the in Secondary Air Injection hose to close the combination valve. (do not use compressed air).

• The combination valve should close and seal. Air should not be able to pass through the combination valve.

- Operate the hand vacuum pump.

• The combination valve should open. Air should be able to pass through the combination valve.

If combination valve does not open:

- Replace the faulty combination valve.

Secondary Air Injection Solenoid Valve, Checking

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Secondary Air Injection (AIR) Solenoid Valve (-N112-) fuse OK.

• The Motronic Engine Control Module (ECM) Power Supply Relay (J271) fuse OK.

• Battery voltage at least 12.5 V.

• All electrical consumers switched off (radiator fan must NOT run during test).

• A/C switched off.

• The ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ General Diagnosis ] General Diagnosis.

Start diagnosis

• Voltage is supplied to the Secondary Air Injection (AIR) Solenoid Valve (N112) from the Motronic Engine Control Module (ECM) Power Supply Relay (J271).

Procedure

- Disconnect the Secondary Air Injection (AIR) Solenoid Valve (N112) electrical harness connector - arrow -.

Checking internal resistance

- Using a multimeter, check the Secondary Air Injection (AIR) Solenoid Valve (N112) terminals 1 to 2 for resistance.

Specified value: 25 to 35 ohms (at approx. 20° C)

If the specified value was not obtained:

- Replace the Secondary Air Injection (AIR) Solenoid Valve (N112).

If the specified value was obtained:

Checking voltage supply

Switch the ignition on.

- Using a multimeter, check the Secondary Air Injection (AIR) Solenoid Valve (N112) electrical connector terminal 1 to Ground (GND) for voltage.

Specified value: battery voltage.

Switch the ignition off.

If the specified value was not obtained:

- Check the wiring from the Secondary Air Injection (AIR) Solenoid Valve (N112) electrical connector terminal 1 to the Motronic Engine Control Module (ECM) Power Supply Relay (J271) terminal 2/87 for a short circuit to Battery positive (+), Ground (GND), or an open circuit.

- Check the electrical harness connector for damage, corrosion, lose or broken terminals.

- If necessary, repair the wiring connection.

If no malfunctions are found in the wiring:

Checking wiring

If the manufacturers test box is being used. Perform the following step.

- Install the test box. Refer to repair information (test box) at Engine Control Module.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Motronic Engine Control Module (ECM) (J220). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.

- Using a multimeter, check the Secondary Air Injection (AIR) Solenoid Valve (N112) electrical harness connector terminal 1 to the Motronic Engine Control Module (ECM) (J220) electrical harness connector T121 terminal 116 for an open circuit.

Specified value: 1.5 ohms Max.

If the specification was not obtained:

- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).

- Check the electrical harness connector for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

- Replace the Motronic Engine Control Module (ECM) (J220). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.

Final procedures

After repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

- End of diagnosis.

Secondary Air Injection Pump Motor, Checking

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Secondary Air Injection (AIR) Pump Relay (-J299-) fuses OK.

• The Motronic Engine Control Module (ECM) Power Supply Relay (J271) fuse OK.

• Battery voltage at least 12.5 V.

• All electrical consumers switched off (radiator fan must NOT run during test).

• A/C switched off.

• The ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ General Diagnosis ] General Diagnosis.

Start diagnosis

- Disconnect the secondary air injection hose - arrow -.

- Remove the center noise insulation fasteners - 1, 2, 3 - and the center noise insulation panel.

- Disconnect the Secondary Air Injection (AIR) Pump Motor (-V101-) electrical harness connector - 3 -.

Checking voltage

- Start engine momentarily.

- Using a Multimeter, check the Secondary Air Injection (AIR) Pump Motor (-V101-) electrical harness connector terminals 1 to 2 for voltage.

- Switch the ignition off.

Specified value: battery voltage.

If the specified value was not obtained:

- Using a Multimeter, check the Secondary Air Injection (AIR) Pump Motor (-V101-) electrical harness connector terminal 2 to Ground (GND).

Specified value: battery voltage.

If the specified value was not obtained:

- Check the wiring connection from the Secondary Air Injection (AIR) Pump Relay (-J299-) socket 5/26 to the Secondary Air Injection (AIR) Pump Motor (-V101-) electrical harness connector terminal 2 for an open circuit or a short circuit.

- Check the wiring connections for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If the specified value was obtained:

Checking Ground (GND)

- Using a Multimeter, check the Secondary Air Injection (AIR) Pump Motor (-V101-) electrical harness connector terminal 1 to Ground (GND) for resistance.

- Connect the secondary air injection hose - arrow -.

Final procedures

After repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

- End of diagnosis.