check engine AUDI A6 1995 C5 / 2.G AEB ATW Engines Secondary Air System Workshop Manual

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Secondary air system, checking
(engine code ATW) Following a cold start, the secondary air system
helps to quickly heat the catalytic converter for
quicker operating readiness.
Principle
Due to over-enrichment of the mixture during the
cold start phase, there is an increased amount of
uncombusted 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 which significantly
improving exhaust quality during the cold start
phase.
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To prevent unnecessary heating, the secondary
air is diverted past the turbocharger -7-. For
this, the charge air pressureregulation pressure
unit opens the charge air pressure valve. The
pressure unit, designed as a double reservoir,
has a vacuum connection for this on the intake
side.
1 -
Secondary Air Injection (AIR) pump relay -
J299-
2 -
Motronic Engine Control Module (ECM) -
J220-
3 -
Secondary Air Injection (AIR) solenoid
valve -N112-
4 -
Intake manifold
5 -
Check valve
Installation position (light/dark side): Arrow
points in direction of flow, as shown
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Checking voltage supply

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

If LED does not light: - Connect VAG1527B voltage tester as follows:Harness connector
terminal
Measure to
1 Engine Ground (GND)
- Operate starter briefly.

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

Check fuse S234 (in fuse holder, position 34).
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If LED does not blink or if it remains constantly
lit:

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM.

If wire connection is OK: - Check the following wire connections for open circuit and short circuit
to Ground (GND) and B+: Harness connector
terminal
VAG1598/31 test box
socket
2 44
- Repair open circuit or short circuit if necessary.
- Replace Engine Control Module (ECM).
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Checking voltage supply of Secondary Air
Injection (AIR) pump relay

- Remove Secondary Air Injection (AIR) pump
relay.

If specified value is not obtained: - Connect multimeter for voltage measurement as follows.3-socket relay carrier in E-box, plenum
chamber, position 2
terminal
Measure to

8 Engine Ground
(GND)

Specified value: approx. battery voltage
- Perform the following tests marked with dots:

Electrical Wiring Diagrams, Troubleshooting & Component Locations Check fuse S130 (40 A) in 3-socket relay carrier in E-Box, plenum
chamber, position 7. Check wire connection from Battery (B+) (terminal 30) to Secondary
Air Injection (AIR) pump relay -J299- (in 3-socket relay carrier in E-
Box, plenum chamber, position 2) for open circuit.
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If specified value is not obtained: - 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.

Specified value: approx. battery voltage
- Perform the 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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Checking activation of the Secondary Air
Injection (AIR) pump relay

- Switch ignition off.

- Remove Secondary Air Injection (AIR) pump
relay.

If LED does not blink: - Connect VAG1527B voltage tester as follows:3-socket relay carrier in E-box, plenum
chamber, position 2
terminal
Measure to

6 Engine Ground
(GND)
- Initiate output Diagnostic Test Mode (DTM) and activate Secondary Air
Injection (AIR) pump relay -J299-.

LED must blink.
- Switch ignition off.
- Connect VAG1598/31 test box at wiring harness to ECM, do not
connect ECM.
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If LED does not light:

- Perform the following tests marked with dots:

Check wire connection from harness
connector at Secondary Air Injection (AIR)
pump motor -V101- to Secondary Air
Injection (AIR) pump relay -J299- (in 3-
socket relay carrier in E-Box, plenum
chamber, position 2) for open circuit.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

Check wire connection from harness
connector at Secondary Air Injection (AIR)
pump motor -V101- to Ground (GND)
connection 1 in engine compartment wiring
harness for open circuit:

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
If no malfunctions are detected:

- Replace Secondary Air Injection (AIR) pump
motor -V101-.
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