Secondary Air Injection Solenoid Valve, Checking

Special tools and workshop equipment 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 PRELIMINARY CHECK .

Start diagnosis 

Procedure 

-- Disconnect the Secondary Air Injection (AIR) Solenoid Valve -N112- electrical harness connector -1-.

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 Ω (at approx. 20 °C)

If the specified value was not obtained:

-- Replace the Secondary Air Injection (AIR) Solenoid Valve -N112- : Refer to appropriate service information.

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 4/85 for 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.

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

-- Remove the Motronic Engine Control Module (ECM) -J220-. Refer to the appropriate service information.

-- Using a multimeter, check the Secondary Air Injection (AIR) Solenoid Valve -N112- electrical harness connector terminal 2 to the Motronic Engine Control Module (ECM) -J220- electrical harness connector T121 terminal 44 for an open circuit.

Secondary Air Injection (AIR) Solenoid Valve -N112- electrical harness connector terminal	Motronic Engine Control Module (ECM) -J220- electrical connector T121 terminal or test box socket
2	44

Specified value: 1.5 Ω 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 appropriate service information.

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 .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .