Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSAUDI2004A8REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEM4.2L - ENGINE MECHANICAL, ENGINE CODE(S): BFM26 - EXHAUST SYSTEM, EMISSION CONTROLSSECONDARY AIR INJECTION (AIR) SYSTEMCOMBINATION VALVE FOR SECONDARY AIR INJECTION (AIR), CHECKING FOR FUNCTION AND LEAKS

2004 Audi A8

Combination valve for Secondary Air Injection (AIR), checking for function and leaks

2004 Audi A8SECTION Combination valve for Secondary Air Injection (AIR), checking for function and leaks

Special tools, testers and auxiliary items required

Fig 1: Hand Vacuum Pump V.A.G 1390

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Hand vacuum pump V.A.G 1390

Test requirements

Vacuum lines and hose connections free of leaks.
Vacuum lines not plugged.

Test sequence

Fig 2: Removing Engine Cover

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Remove engine cover - 1 - upward.

Fig 3: Disconnecting Vacuum Hose At Combination Valve To Be Tested

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Disconnect vacuum hose - arrow - at combination valve to be tested.
Connect hand vacuum pump V.A.G 1390 to vacuum hose of combination valve to be checked.

NOTE:

Illustration depicts engine from rear.
Left combination valve is shown in illustration.

For vehicles with parking/auxiliary heater:

Fig 4: Removing Bolts For Exhaust Pipe Of Parking Heater/Auxiliary Heater On Noise Insulation

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Remove bolts - arrows - for exhaust pipe of parking heater/auxiliary heater on noise insulation.

All

Fig 5: Locating Mounting Parts And Removing Noise Insulation

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Remove noise insulation - 1 -.

Fig 6: Disconnecting Intake Air Duct At Secondary Air Injection (AIR) Pump Motor V101

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Disconnect pressure hose - 2 - at Secondary Air Injection (AIR) Pump Motor V101 and blow into it with light pressure (do not use pressurized air).

Both combination valves must be closed, it must not be possible to blow through hose.

Operate hand vacuum pump.

The relevant combination valve must open, it must not be possible to blow through

If relevant combination valve does not open:

Replace combination valve, left → Secondary Air Injection (AIR) (left combination valve), removing and installing or right → Secondary Air Injection (AIR) (right combination valve), removing and installing .

RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.