ignition AUDI A8 1998 D2 / 1.G AEB Engine Motronic MFI And Ignition System

24-1


Motronic Multiport Fuel
Injection (MFI) and ignition
system Component locations, overview

----
Data Link Connector (DLC)
Located under knee bar, left side of
steering wheel
----
Fuel pump relayPosition 6 on relay panel in driver's side
footwell
----
Oxygen Sensor (O2S) behind Three Way
Catalytic Converter (TWC) -G130- with
Oxygen Sensor (O2S) heater -Z29- In exhaust system behind TWC
----
EVAP system Leak Detection Pump (LDP)
-V144- In left-rear wheelhousing behind splash
shield
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24-3


5 -
EVAP canister purge regulator valve -N80-
6 -
Power output stage -N122-
5-pin connector: signal wiring from ECM4-pin connector: coil primary circuit
connections
7 -
Mass Air Flow (MAF) sensor -G70- In upper air cleaner housing
8 -
Wastegate bypass regulator valve -N75-
9 -
Ignition coils Cylinder 1: -N-Cylinder 2: -N128-Cylinder 3: -N158-Cylinder 4: -N163-
10 -
Fuel injectors Cylinder 1: -N30-Cylinder 2: -N31-Cylinder 3: -N32-Cylinder 4: -N33-
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24-5

Safety precautions


WARNING!

Fire hazard! Do not smoke, work near heaters
or open flame, or have anything nearby that
could ignite fuel. The fuel system is under
pressure. Before opening, cover connections
with a rag, and open carefully to release
pressure. Be alert when working on or near
the engine and ignition wires. High secondary
ignition voltage can cause serious personal
injury and damage vehicle components.

DO NOT touch or disconnect ignition system
wires when the engine is running or being
cranked at starting RPM.
DO NOT operate starter if fuel injectors are
removed.

Be sure the ignition is switched OFF, when:
Disconnecting or connecting the battery,
ignition wires, or test equipment leads
Disconnecting fuel injection system wiring
Washing the engine or engine
compartment.
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BEFORE cranking engine at starting RPM
(e.g. for compression testing) disable ignition
and fuel injection systems:

Disconnect both ignition coil power output
stages, and both Motronic fuses at the E-box
in the plenum.
Disconnect harness connectors from all fuel
injectors.
Afterward, erase DTC memory.
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24-6

CAUTION!

BEFORE disconnecting the battery:

Stop the engine.
Be sure the ignition is switched OFF (also
applies when connecting the battery). Failure
to do so may damage the Engine Control
Module (ECM).
Be sure of the proper radio code (for vehicles
equipped with coded anti-theft radio).

Be sure the battery negative (-) cable is
disconnected, when:
Working on the electrical system
Resistance (spot) welding or electric arc
welding anywhere on the vehicle.

When connecting and disconnecting
electrical test equipment (LED voltage tester,
multimeter, etc.):
Be sure the ignition is switched OFF.
Use correct adapters from the VW 1594
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connector test kit.

For any work affecting the Engine Control
Module (ECM):
BEFORE disconnecting the ECM harness
connector, switch the ignition OFF and WAIT
at least 20 seconds. Failure to do so may
damage the ECM.
DO NOT connect any outside voltage source
to stimulate an output signal at the ECM.
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24-9

Fuel injection system, servicing

Servicing ignition system:

Repair Group 28

Notes:

Fuel hoses in the engine compartment must be
secured with spring-type clamps. Screw-type
clamps or equivalent must not be used.
The Engine Control Module (ECM) has On
Board Diagnostic (OBD) capability, and is
equipped with Diagnostic Trouble Code (DTC)
memory. Before repairing or adjusting any
components or systems, first check DTC
memory. Also check all vacuum connections for
leaks ("false air").
For proper operation of electrical and electronic
components, a Battery Positive Voltage (B+)
supply of at least 11.5 volts is required.
Do not use any gasket sealers or other
automotive chemical compounds that contain
silicone. Traces of silicone drawn into the
engine pass unburned into the exhaust and can
damage the oxygen sensors.
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24-11

Idle speed, checking


Notes:

Idle speed, ignition timing and CO-content
cannot be adjusted.
Idle speed is maintained by the Throttle valve
control module.
CO-content is maintained and adjusted by
Oxygen Sensor (O2S) control. Malfunctions in
O2S control are recognized by On Board
Diagnostic (OBD) and stored in DTC memory.

Required special tools and test equipment
VAG 1551 Scan Tool (ST) with VAG 1551/3
adapter cable

Test conditions
No malfunctions stored in DTC memory
Page 01
-15


Engine Coolant Temperature (ECT) at least
85 C (185 F)

All electrical consumers switched off
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24-21

Continuation
If the value in display field 1 is NOT OK, or if the
value does not fluctuate by at least 2 %:

- Road test to condition oxygen sensor (eliminate
possible contamination) and repeat test.
If the value in display field 1 is still NOT OK, or if
it still does not fluctuate by at least 2 %:

- Check Oxygen Sensor (O2S) heater Page 24
-
27
.
If the value in display field 1 remains constant:

- Check oxygen sensor voltage (display field 2).

-
Press button to advance program
sequence.
- Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
input.

- Switch ignition off.
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24-24

Checking HO2S reference voltage

- Disconnect 4-pin connector -1- (brown) for
HO2S -G39-.

If voltage is NOT OK:
If voltage is OK: - Connect multimeter US 1119 (Fluke 83 or equivalent) between harness
connector terminals 3 and 4 (to ECM), using adapter cables from VW
1594 connector test kit.
- Start engine and measure voltage.
Specified value: 0.40-0.50 volts
- Switch ignition off.
- Check HO2S wiring Page 24
-25
- Replace Heated Oxygen Sensor (HO2S) -G39-.
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port Fuel In
jection
(MFI
) and i
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11/19/2002 htt
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yp
e=re
pair&id=AUDI.B5.FU02.24.1