display AUDI A6 1995 C5 / 2.G ATQ Engine Motronic Injection System Servicing Workshop Manual

24-21

Engine Control Module (ECM), replacing


Special Tools and Equipment

Removing
VAS5051 with VAG5051/1
orVAG1551 with VAG1551/3B
- Connect VAS5051 tester or VAG1551 scan tool and select the control
module for engine electronics using "address word" 01 Page 01
-9 .
Ignition must remain switched on for this.
3B0907551BA
2.8l V6/5V
G
0003
Coding 07252
WSC 12345

VAG1551 Scan Tool (ST) display indicates control module identification,
e.g.:
- First, always allow display of control module identification and print it
out Page 01
-11
.
- Compare coding with coding versions Page 01
-73
.
- Switch ignition off.
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24-26

Notes:

Idle speed cannot be adjusted.
Idle speed is checked during basic setting of
the engine.
During basic setting, the Evaporative Emission
(EVAP) canister purge regulator valve (EVAP
valve -N80-) is closed and the A/C compressor
is switched off

Test sequence

- Check DTC Memory Page 01
-15
. There must
not be any DTCs stored, repair malfunctions if
necessary, erase DTC memory, switch engine
off and start again, road test vehicle and check
DTC memory again as a control measure.

- Let engine continue to run at idle.

CAUTION!

The electric cooling fan must not run. Rapid data transfer
HELP
Select function XX

When indicated on display:
- Press buttons -0- and -4- to select "Initiate basic setting" and press -Q-
button to confirm input.
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Basic Settin
g
Q
Input display group number XXX

When indicated on display:
- Press buttons -0-, -5- and -6- to select "display group number 056" and press -Q-
button to confirm input.
System in Basic Setting 56
1
2
3
4

When indicated on display:
- Check whether the engine speed in display field 1 (actual engine speed) is within
tolerated range.

Display fields

1 2 3 4
Display group 056: Idle stabilization with engine at idle and operating temperature
Display
xxx /min
xxx /min x.x % X X X X X
Indicated
Engine speed (actual)
Engine speed
(specified) Idle control
Torque
change Operating conditions
Specified
value 720 to 820 RPM
1)
630 to 730 RPM 2) 770 RPM
1)
680 RPM 2) -5 to 5 % 0 0 0 0 0
Notes
If specified value is not obtained
Page 24
-29

Significance of
numbers
Page 24
-29

1) Front Wheel Drive Vehicles
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Notes:

Engine speed in display field 1 (actual engine
speed) is the current engine speed.
Engine speed in display field 2 (specified
engine speed) is a theoretical engine speed
calculated by the ECM.
At idle, the ECM always attempts to adapt the
engine speed (actual) to the specified engine
speed (specified).
This means that the engine speed (actual) must
always approximately match the engine speed
(specified) at idle.
Display fields 3 and 4 provide information, but
are not relevant for checking idle speed.
If specified value is obtained:

-
Press button.
Rapid data transfer
HELP
Select function XX

Indicated on display (function selection):
If specified value is not obtained:
- Check DTC memory again Page 01
-15
.
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If idle speed is too high or low and there are
no DTCs in DTC memory, the following tests
(marked with dots) must be performed:

False air in intake air system, checking
Page 24
-64
.

Throttle valve control module, checking
Page 24
-141
.

Evaporative Emission (EVAP) canister purge
regulator valve always open, checking
Page 24
-128
.

Perform adaptation of throttle valve control
module Page 24
-142
.
Significance of 5 digit indication of display group 056 x
x
x
x
x
Display field 4
0 A/C compressor
0 = A/C compressor off
1 = A/C compressor on
0 Driving mode selected
0 = selector lever in P or N
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- Start engine and let run at idle.

The following malfunction are possible if the pressure does not drop:
Repair Manual, Fuel Supply System, Repair Group 20; Fuel supply
-
Front Wheel Drive or fuel supply
- All Wheel Drive

Note:
Pressure gauge displays the pressure behind the stopcock "intake
manifold side" after the stopcock is closed (in direction of fuel injector, fuel
pressure regulator). If the pressure drops in front of the stopcock (in
direction of fuel tank), the device cannot detect it. For this reason, the
center of this page states "If the pressure does not drop...". - Wait until pressure has dropped, and then switch off ignition.
Simultaneously close shut-off valve of VAG1318 pressure gauge (lever
perpendicular to direction of flow -arrow-).
There is a leak in the threaded connection between the pressure
gauge and the fuel supply line There is a leak at the supply line at fuel tank.There is a leak in the check valve in the Fuel Pump (FP).
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Test requirements:

Coolant Temperature at least 80 C.

Electrical consumers switched off (radiator
fan must NOT run during test).
A/C switched off.
Fuse for Mass Air Flow (MAF) sensor OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations binder

Checking function

- Connect VAS5051 tester or VAG1551 scan tool
and select the control module for engine
electronics using "address word" 01 Page 01
-
9 .

Engine must run at idle for this.Rapid data transfer
HELP
Select function XX

When indicated on display:
-
Press buttons -0- and -4- to select "Initiate basic setting" and press -Q-
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Basic Settin
g
Q
Input display group number XXX

When indicated on display:
- Press buttons -0-, -0- and -2- to select "display group number 002" and press -Q-
button to confirm input.
System in Basic Setting 2
1
2
3
4

When indicated on display:
- Check specified values for load detection in display fields 3 and 4.

Display fields

1 2 3 4
Display group 002: Air mass taken in with engine at idle and operating temperature
Display xxx /min xx.x %
x.x ms
xxx.x g/s
Indicated Engine speed
(RPM) Load
mean injection time
Air mass
Functional
range 630 to 6800
RPM 12 to 100
% 1.0 to 20.0 ms
1.0 to 150 g/s
Specified
value 720 to 820
RPM
1)
630 to 730
RPM2) 12.0 to
26.0 % 1.0 to 4.0 ms
1.0 to 5.0 g/s
Notes --- ---
If specified value is not obtained:
Evaluation display field 3 Page 24
-
59

If specified value is not obtained:
Evaluation display field 4 Page 24
-
60

1) Front Wheel Drive Vehicles
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If specified values are obtained:

-
Press button.Rapid data transfer
HELP
Select function XX

Indicated on display (function selection):
Evaluation display group 002
Display field: 3
Possible cause
Corrective action
less than 1.0
ms
Smaller values are only possible when driving in
deceleration mode
larger than 4.0
ms Engine under load due to power accessories.- Reduce load (A/C system/power
steering/generator)

Poor idle (does not run on all cylinders)- Check spark plugs.
- Check fuel injectors Page 24
-36


Throttle valve control module - J338- faulty- Check throttle valve control module Page
24
-141

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Evaluation display group 002 Display field:
4
Possible cause
Corrective action
smaller than
1.0 g/s
large false air mass between intake manifold and Mass Air
Flow (MAF) sensor
Voltage supply of Mass Air Flow (MAF) sensor or wire
connections to Engine Control Module (ECM) - Check intake system for leaks (false
air) Page 24
-64

- Check voltage supply Page 24
-61
larger than 5.0
g/s
Engine under load due to power accessories.- Reduce load (A/C system/power
steering/generator)

Voltage supply of Mass Air Flow (MAF) sensor or wire
connections to Engine Control Module (ECM) - Check voltage supply Page 24
-61
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