sensor AUDI A3 1999 8L / 1.G ATW Engine Electronic Power Control Checking Workshop Manual

24-113


Electronic Engine Power
Control (EPC) (E-Gas),
checking

E-Gas system, function

For E-Gas, the throttle valve is not operated by a
cable from the accelerator pedal. There is no
mechanical connection between the accelerator
pedal and the throttle valve.
The position of the accelerator pedal is
communicated to the Engine Control Module
(ECM) via two sensors for accelerator pedal
position (variable resistances; stored in one
housing) that are connected with the accelerator
pedal.
The accelerator pedal position (driver's intention)
is a main input unit for the ECM.
Operation of the throttle valve occurs via an
electric motor (throttle valve actuator) in the
throttle valve control module. This is true across
the entire engine speed and engine load
spectrum.
The throttle valve is operated by the throttle valve
actuator according to the instructions of the
ECM.
With ignition switched on and engine off, the
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ECM activates the throttle valve actuator
precisely according to the sensor for accelerator
pedal position. This means, if the accelerator
pedal is depressed half way, the throttle valve
actuator opens the throttle valve to the same
degree; i.e. throttle valve would be opened half
way.
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With engine running (under load), the ECM can
open or close the throttle valve independently of
the sensor for accelerator pedal position.
This means, for example, that the throttle valve
could be fully opened even though the
accelerator pedal has only been depressed half
way. This has the advantage of preventing
torque losses at the throttle valve.
In addition to this, it results in significantly better
values relative to emissions and consumption
under certain load conditions.
The required engine torque can be achieved by
the Engine Control Module (ECM) via the optimal
combination of throttle valve diameter and boost
pressure.
It would be incorrect to think that "E-Gas"
consists of only one or two component. E-Gas is
much more of a system containing all
components that contribute to recognizing,
controlling and monitoring the position of the
throttle valve, e.g. sensor for accelerator pedal
position, throttle valve control module, EPC
warning lamp, Engine Control Module (ECM).
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24-120

Throttle valve control module -J338-,
checking

The following components are located in the
housing for the throttle valve control module:

Throttle drive (power accelerator actuation) -
G186-. (This is an electric motor that is
activated by the ECM. This electric motor opens
the throttle valve against spring pressure.)
Angle sensor -1- for throttle drive (power
accelerator actuation) -G187-
Angle sensor -2- for throttle drive (power
accelerator actuation) -G188-

Note:
The housing for the throttle valve control
module must not be opened.
The angle sensors are designed as
potentiometers (variable resistances). They
communicate the position of the throttle valve to
the Engine Control Module (ECM) fully
independent of each other.
The potentiometers cannot be mechanically
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24-121

Throttle valve control module, adapting

The adaptation teaches the Engine Control
Module (ECM) various positions of the throttle
valve when the ignition is on and the engine is
stopped. These positions are stored in the
control module The return communication
regarding the position of the throttle valve occurs
via the two angle sensors for throttle drive.
An adaptation must always be performed when
the throttle valve control module -J338- or the
Engine Control Module (ECM) are removed and
installed (or replaced) or if voltage supply to the
Engine Control Module (ECM) is interrupted.
The learning process (adaptation) occurs:

automatically if the ignition is switched on for at
least 10 seconds without operating starter and
accelerator pedal and the Engine Control
Module (ECM) recognizes "adaptation
required". (There will be no notification of
whether adaptation was successful or not
however). Adaptation required is recognized if
stored voltage values from the angle sensors
do not match actual measured voltage values
within a certain tolerance range.
via initiation of basic setting (function 04)
display group 060 with ignition on.
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24-123

Procedure

- Connect VAS5051 tester or VAG1551 scan tool
and select control module for engine electronics
using "address word" 01 Page 01
-10
. Ignition
must remain switched on.
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.
Basic Settin
g
Q
Enter displa
y group number XXX

When indicated on display
After pressing Q-button, throttle valve actuator will be switched on without
current.
In this condition, the throttle valve will be drawn into an emergency
position by a mechanical spring, which is located in the throttle valve
control module. The values supplied by the two angle sensors in this
emergency position are stored by the Engine Control Module (ECM). - Press buttons -0-, -6- and -0- to select "display group number 060" and
press -Q- button to confirm input.
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Next, the throttle valve is opened by a certain
value. If this value is reached, the throttle valve
actuator is once again de-energized. Now, the
mechanical spring must close the throttle valve to
the previously learned emergency position within
a specified time (spring test).
Then, the throttle valve is closed by the throttle
valve actuator; the values supplied by the angle
sensors in the throttle valve control unit are
stored by the Engine Control Module (ECM).
If Engine Control Module (ECM) should de-
energize throttle valve actuator during driving
operation, this is expressed by an increased,
surging idle speed (RPM). The engine accepts
gas only after great delay. System in basic setting 60
1
2
3
4

When indicated on display
- Check specified values for throttle valve control module in display fields
3 and 4.
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Display fields

1 2 3 4
Display group 060: Adaptation of throttle valve control module
Display xx % xx %
x
---
Indicated Throttle
valve angle
(angle
sensor 1) Throttle
valve angle
(angle
sensor 2) Adaptation step counter
Adaptation condition
Functional
range
0 to 8
ADP in progress
ADP OK
ERROR
Specified
value 3 to 93 % 97 to 3 %
8
ADP OK
Note


After adaptation, the adaptation step
counter reaches the number 8 (it is OK for
numbers to be skipped). If "ERROR." is displayed:
Check DTC memory Page
01
-16
.
If specified value is not
obtained: Note, Page 24
-
126

Note:
The abbreviation "ADP" in display field 4 stands for "Adaptation".
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24-127


Angle sensor -1- for throttle drive,
checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3A
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24-128
Angle sensor 1 for throttle drive (power
accelerator actuation) -G187- and angle sensor 1
for throttle drive (power accelerator actuation) -
G188- inform the Engine Control Module (ECM)
about the position of the throttle valve. Both
angle sensors are located in the throttle valve
control module.

Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select control module for engine electronics
using "address word" 01 Page 01
-10
. Ignition
must remain switched on.
Rapid data transfer
HELP
Select function XX

When indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
Read measuring value block
Q
Enter displa
y group number XXX

When indicated on display
- Press buttons -0-, -6- and -2- to select "display group number 062" and
press -Q- button to confirm input.
Read Measuring Value Block 62
1
2
3
4

Indicated on display
- Check specified values for E-gas potentiometer voltages in display
fields 1 and 2.
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