1996 AUDI A4 start

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Secondary air system The secondary air system results in quicker heating
and therefore earlier operating readiness of the
catalytic converter following cold start.
Principle
Due to over-enrichment of the mixture during the
cold start phase, there is an increased amount of
un-combusted carbon monoxide in the exhaust.
Secondary Air Injection (AIR) improves secondary
oxidation in the catalytic converter and therefore
reduces emissions. The heat produced by
secondary oxidation greatly reduces start-up time
for the catalytic converter, therefore improving
exhaust quality during the cold start phase
significantly.
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Function:

In the cold start phase, the ECM -4- activates
the secondary air pump -2- via the relay for
secondary air pump -3-. Air reaches the
combination valves for Secondary Air Injection
(AIR) -5- and -9-.
The Secondary Air Injection (AIR) valve -6- is
activated in parallel, which allows the vacuum to
reach the combination valves for Secondary Air
Injection (AIR) -5- and -9-. The appropriate
combination valve for Secondary Air Injection
(AIR) thereby opens the path for secondary air
to the exhaust channels of the cylinder head.
1 -
Secondary Air Injection (AIR) pump relay -
J299-
Removing and installing Page 26
-37
checking Page 26
-45
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Checking voltage supply

- Disconnect connector from Secondary Air
Injection (AIR) solenoid valve -N112-.

If LED does not light: - Connect VAG 1527B voltage tester as follows:Harness connector terminal
Measure to
1 Engine Ground (GND)
- Operate starter briefly.

LED must light.
- Perform following tests marked with dots:

Check fuse -S234- (in fuse holder, position 34).
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26-48

- Connect multimeter for voltage measurement as
follows:

3-socket relay carrier in E-box,
plenum chamber, position 2
terminal
Measure to

4 Engine
Ground
(GND)

- Operate starter briefly.


Specification: approx. battery voltage
If specified value is not obtained:

- Perform following tests marked with dots:

Electrical Wiring Diagrams, Troubleshooting & Component Locations Check fuse -S234- (in fuse holder, position 34). Check wire connection from Secondary Air Injection (AIR) pump relay
-J299- (in 3-socket relay carrier in E-box, plenum chamber) via fuse -
S234- (in fuse holder, position 34) to Fuel Pump (FP) relay for open
circuit:
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