fuel AUDI A6 1998 C5 / 2.G ATQ Engine Motronic Injection System Servicing Workshop Manual

24-1


Motronic injection system,
servicing

Safety precautions

If special testing equipment is required during
road test, note the following:

WARNING!

Scan tools and testing devices must always
be secured on the rear seat and operated
from there by a second person.
If a scan tool or testing device were to be
operated from the passenger seat and there
were an accident involving activation of the
passenger-side airbag, the person seated
there could be seriously injured.
To reduce the risk of personal injury and/or
damage to the fuel injection and ignition system,
always observe the following:
Only disconnect and reconnect wires for
injection and ignition system, including test
leads, when ignition is turned off.
If engine is to be cranked at starting RPM
without starting (e.g. for compression testing),
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disconnect connector from ignition coils and
from fuel injectors.
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24-2

It is possible that the control module will
recognize a malfunction and store a DTC during
some tests. After completing all tests and
repairs, DTC memory should therefore be
checked and erased if necessary. Readiness
code must be generated after DTC memory is
erased Page 01
-82
.

Always switch ignition off before cleaning
engine.
The battery should only be disconnected and
reconnected when the ignition is turned off,
since otherwise the Engine Control Module
(ECM) can be damaged.

WARNING!

Fuel system is under pressure! Place a cloth
around the connection point before opening
system. Then release pressure by carefully
loosening connection point.
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24-3

Rules of cleanliness

When working on the fuel supply or fuel injection
systems, the following "6 rules of cleanliness"
should be carefully observed:

Thoroughly clean all connections and the
surrounding area before disconnecting.
Place parts that have been removed on a clean
surface and cover. Use lint-free cloths only!
Carefully cover opened components or seal
them if repairs are not carried out immediately.
Only install clean components: Only unpack
replacement parts immediately prior to
installation. Do not use parts that have been
stored loose (in tool boxes etc.)
When the system is open: Do not work with
compressed air if it can be avoided. Do not
move vehicle unless absolutely necessary.
Disconnected electrical harness connectors:
Protect from dirt and moisture. Be sure harness
connector is dry before connecting.
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24-4
Technical data

Engine identification

ATQ (2.8 L / 5V/ 147 kW-engine)
Idle speed
Engine speed cannot be adjusted, it is regulated by idle
stabilization

720 to 820 RPM (front wheel drive)
630 to 730 RPM (all wheel drive)
Engine speed (RPM) limitation
via fuel injector shut-off
about 6800 RPM
Fuel pressure at idle speed Vacuum hose
connected
3.2 to 3.8 bar

Vacuum hose
disconnected
3.8 to 4.2 bar
Residual pressure after 10 min. cold engine about 2.2 bar positive pressure

warm engine about 3.0 bar positive pressure
Fuel injectors Injection stream Dual-hole nozzle / same for all
injectors

Injection quantity (30
s) 90 to 125 ml.

Resistance
(room temperature)
1)
13.5 to 15.5
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1) With an engine at normal operating temperature, the resistance of the fuel injectors increases by approx. 4 to 6
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24-9


17 -
Engine Coolant Temperature (ECT) sensor
-G62-
for Engine Control Module (ECM)At coolant line behind cylinder head engine
bank 1 with Engine Coolant Temperature (ECT)
Sensor -G2- Checking Page 28
-23
If necessary, release pressure in cooling
system before removing
18 -
Throttle valve control module -J338- With throttle drive (power accelerator
actuation) -G186-, angle sensor -1- for
throttle drive (power accelerator actuation)
-G187-, and angle sensor -2- for throttle
drive (power accelerator actuation) -G188-
19 -
Intake Manifold Change-Over Valve -N156-
20 -
Fuel pressure regulator
21 -
Engine Speed (RPM) sensor -G28- in transmission housing via ring gearChecking Page 28
-19
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24-10


22 -
Camshaft Position (CMP) sensor 2 -G40-
Bank 2
23 -
Heated Oxygen Sensor (HO2S) 2 -G108-
before catalytic converter with Oxygen
Sensor (O2S) 2 Heater -Z28- Bank 2, sensor 1
24 -
Knock Sensor (KS) 2 -G66-
25 -
Ignition coils (-N-, -N128-, -N158-) with power output stage -N122-
26 -
Knock Sensor (KS) 1 -G61-
27 -
Fuel injectors -N30- through -N33-
,Cylinder 5/6 Fuel Injector -N83-, -N84-
28 -
Valve -1- for camshaft adjustment -N205-
29 -
Secondary Air Injection (AIR) pump
motor-V101-
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24-12


Note:
In order to assure sufficiently secure fitting, switches must not be installed
more than once.
Adjusting switch:
Repair Manual, Brake System, ABS, ABS/EDL, Repair Group 46
Fig. 9 Component location Brake Light Switch -F- and Brake
Vacuum Vent Valve Switch For Cruise Control/Diesel Fuel
Injection, Clutch Vacuum Vent Valve Switch -F36-
1 - Clip
2 - Brake Light Switch -F-, Brake Vacuum Vent Valve Switch For Cruise
Control/Diesel Fuel Injection -F47-
3 - Clutch vacuum vent valve switch -F36-

Secondary Air Injection (AIR) Pump Relay -J299- (arrow) in 3-pin relay
carrier in E-box, plenum chamber. Fig. 10 Component location for Secondary Air Injection (AIR)
Pump Relay -J299-
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24-13


Fuel Pump (FP) Relay -J17- is located at position 4 of central electrics in
driver's footwell, left. Fig. 11 Component locations Fuel Pump (FP) Relay -J17-

Data Link Connector (DLC) in knee bolster on driver's side. Fig. 12 Component location of Data Link Connector (DLC)
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