engine 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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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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24-4
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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24-7


5 -
Secondary Air Injection (AIR) solenoid
valve -N112-
6 -
Intake Air Temperature (IAT) sensor -G42-
7 -
4-pin harness connector
for Heated Oxygen Sensor (HO2S) 2 -
G108- before catalytic converter and
Oxygen Sensor (O2S) 2 Heater -Z28-
(bank 2 sensor 1) Black
8 -
3-pin harness connector for engine speed (RPM) sensor -G28-gray
9 -
3-pin harness connector for Knock Sensor (KS) 2 -G66-blue
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24-8


10 -
E-box in plenum chamber
Motronic Engine Control Module (ECM) -
J220- Secondary Air Injection (AIR) Pump Relay -
J299- Fig. 10
, page Page 24
-12

11 -
Valve -2- for camshaft adjustment -N208-
12 -
Camshaft Position (CMP) sensor 2 -G163-
Bank 1
13 -
Heated Oxygen Sensor (HO2S) -G39-
before catalytic converter with Oxygen
Sensor (O2S) Heater -Z19- Bank 1, sensor 1
14 -
Ground connection on the engine bracket, right side
15 -
Mass Air Flow (MAF) sensor -G70- Checking Page 24
-56
16 -
Evaporative Emission (EVAP) canister
purge regulator valve -N80-
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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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24-17

Wire and component test using
VAG1598/31 test box


Notes:

VAG1598/31 test box is designed so that it can
be simultaneously connected to the wiring
harness at the Engine Control Module (ECM)
and also to the ECM itself.
This is advantageous because electronic
engine control remains fully functional (e.g.
measurement of signals with engine running)
when the test box is attached.
Relevant test procedures note whether Engine
Control Module (ECM) should also be
connected to the test box or not.
Always use VAG1594A connector test kit to
attach measurement devices (e.g. VAG1527B
voltage tester, VAG1526 multimeter etc.).

CAUTION!

To reduce the risk of damaging electronic
components, set the tester to the approprate
test range and observe test requirements
before connecting test leads.
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24-19


- Remove Heater Core E-box cover -arrows-.

Note:
Adaptation values are erased when connector is disconnected from the
Engine Control Module (ECM), DTC memory content remains intact. - Using a screwdriver, carefully pry off retaining bracket (arrow).
- Disengage locking lugs and remove control module connector.
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24-20


Important note:
After re-connecting the Engine Control Module (ECM), the following work
steps must be performed:
- Check DTC memory and erase it if necessary Page 01
-15
.
- Perform adaptation of the Throttle Valve Control Module -J338- Page
24
-142
.
Note:
In the first adaptation phase during engine basic setting, it is possible that
idle will be rough and vehicle may shake lightly in drive mode. - Connect VAG1598/31 test box to connector of wiring harness. Ground
(GND) clip at test box (not visible in illustration) must be connected to
Ground (GND). Relevant test procedures note whether Engine Control
Module (ECM) should also be connected to the test box.
- Perform test as described in relevant repair sequence.
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