sensor AUDI A4 1997 B5 / 1.G APB Engine Electronic Engine Power Control Checking Workshop Manual
[x] Cancel search | Manufacturer: AUDI, Model Year: 1997, Model line: A4, Model: AUDI A4 1997 B5 / 1.GPages: 39, PDF Size: 0.16 MB
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24-139
 
     
Electronic Engine Power 
Control (EPC), checking 
     
Function of Engine Power Control (EPC)
 
      With the electronic throttle, the throttle valve is 
not operated by a cable connected to the 
accelerator pedal. There is no mechanical link 
between the accelerator pedal and the throttle 
valve.  
      The throttle valve is actuated by a servomotor 
(throttle valve positioner) in the throttle valve 
control module over the full range of engine 
speeds and load conditions.  
      The throttle valve positioner actuates the throttle 
valve according to the commands it receives 
from the Engine Control Module (ECM).  
      The position of the accelerator pedal is 
communicated to the Engine Control Module 
(ECM) by two accelerator position sensors 
(variable resistors, both installed in a single 
housing) which are connected to the accelerator 
pedal.  
      The accelerator pedal position (as determined by 
the driver) is one of the main input values for the 
Engine Control Module (ECM).  
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24-140
       With the engine is not running and the ignition 
switched on, the ECM operates the throttle valve 
positioner in exact accordance with the signals 
from the accelerator position sensors. For 
example, when the accelerator pedal is pressed 
down half way, the throttle valve positioner opens 
the throttle valve by an equivalent amount, i.e. 
about half way.  
      When the engine is running (i.e. under load) the 
ECM can open and close the throttle valve freely, 
independently of the signals being sent by the 
accelerator position sensors.  
      For example, the throttle valve might already be 
fully open even though the accelerator pedal is 
only pressed down half way. This has the 
advantage of preventing throttling losses at the 
throttle valve.  
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24-141
       Under certain engine load conditions there is 
also a significant reduction in harmful emissions 
and noticeably improved fuel consumption.  
      The Engine Control Module (ECM) can provide 
the optimum combination of throttle valve 
opening and charge pressure in order to create 
the required torque.  
      The electronic throttle is not simply a 
combination of two or three components, but 
rather a complete system comprising all the 
elements that together determine the position of 
the throttle valve and also control and monitor it. 
For example, the Accelerator Pedal Position 
Sensor, Throttle Valve Control Module, EPC 
warning lamp, Engine Control Module (ECM) 
etc.  
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24-145
      
Throttle Valve Control Module -J338, 
checking
 
      The throttle valve control module housing 
contains the following components:  
     
CAUTION! 
     
The housing should NOT be opened. 
     
Throttle drive -G186 (power accelerator 
actuation) (This is an electric motor activated by 
the engine control module. The motor opens 
the throttle valve by applying force to overcome 
the spring pressure.) 
     Angle sensor -1- for throttle drive (power 
accelerator actuation) -G187 
     Angle sensor -2- for throttle drive (power 
accelerator actuation) -G188 
     
Notes:  
     The angle sensors are in the form of 
potentiometers (variable resistors). Each sends 
its own separate signal to inform the engine 
control module of the position of the throttle 
valve (i.e. one of the signals is redundant). 
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Page 11 of 39

24-146
      
Throttle valve control module, 
adaptation
 
      The adaptation process enables the Engine 
Control Module (ECM) to learn the different 
positions of the throttle valve with the ignition 
switched on and the engine not running. These 
positions are stored in the control module. The 
feedback signal indicating the position of the 
throttle valve comes from the two angle sensors 
for throttle valve drive.  
      If the Throttle Valve Control Module -J338 or the 
ECM is removed and installed or replaced, or if 
the voltage (power) supply to the ECM is 
interrupted, an adaptation must be carried out.  
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24-147
       The learning process (adaptation process) is 
carried out:  
     
By selecting "Basic Setting" (function 04), 
Display Group 060 with the ignition switched 
on. 
     Automatically if the ignition is switched on for at 
least 6 seconds without operating the starter or 
depressing the accelerator, and if the Engine 
Control Module (ECM) registers a "learning 
requirement." (In this case, however, there is no 
way of knowing whether the adaptation process 
was successful or not.) The engine control 
module will register a learning requirement if 
the previously stored voltage readings from the 
angle sensors do not correspond (within a 
certain tolerance range) to the new voltage 
readings. 
     
Note:  
     The engine will not start during automatic 
adaptation. 
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Page 15 of 39

24-150
       When the -Q- button is pressed the throttle valve 
positioner will be switched mechanically.  
      In this condition the throttle valve is pulled into an 
"emergency running" or default position by a 
mechanical spring in the throttle valve control 
module. The values supplied by the two angle 
sensors for this emergency running position are 
stored in the Engine Control Module (ECM).  
      The throttle valve is then opened by a 
predetermined amount. As soon as it reaches 
this position the current supply to the throttle 
valve positioner is again disconnected. The 
spring should then close the throttle valve 
mechanically to the previously learned default 
position within a specified period of time (spring 
test).  
      The throttle valve positioner then closes the 
throttle valve and the values supplied by the 
angle sensors in the throttle valve control module 
are stored in the Engine Control Module (ECM).  
      If the ECM disconnects the current supply to the 
throttle valve positioner while the vehicle is being 
driven, the result will be an increase in idling 
speed with fluctuating engine RPM (hunting) and 
very slow throttle response.  
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-  Check specification for throttle valve control 
module (display fields 4). 
  
Display fields  
  
1   2   3   4  
Display Group 060: Adaptation of throttle valve control module with ignition on  
Display   xx %   xx %  
---  
---  
Indicates  Throttle 
valve angle  
(angle 
sensor 1)  Throttle 
valve angle  
(angle 
sensor 2)  Learning stage counter  
Adaptation status  
Work 
Range  min.: 0 %  
max.: 100 
%  min.: 0 %  
max.: 100 
%  0 to 8  
ADP. runs  
ADP. O.K.  
ADP. ERROR  
Specified 
value  3 - 20 %   80 - 97 %  
8  
ADP. OK  
Note        
Learning stage counter must run from 0 to 8 
during adaptation process (some digits may 
also skip).  If specification is not met: 
Notes  Page 24
-152
 .  
Note:  
 
It is not important how the learning stage counter reacts during adaptation, rather the specification "ADP" is reached after 
the adaptation in display field 4. 
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24-153
      
Angle sensor -1- for throttle drive 
(power accelerator actuation) -G187- 
and angle sensor -2- for throttle drive 
(power accelerator actuation) -G188, 
checking
 
      The angle sensor -1- for throttle drive (power 
accelerator actuation) -G187 and angle sensor -
2- for throttle drive (power accelerator actuation) 
-G188 inform the engine control module of the 
position of the throttle valve. Both angle sensors 
are located in the throttle valve control module.  
     
-  Connect vehicle diagnostic, testing and 
information system VAS 5051 or VAG1551 scan 
tool and select engine electronics control 
module by entering address word "01"   Page 
01
-9 . When doing this the ignition must be 
switched on. 
Rapid data transfer 
HELP
Select function XX
    
Indicated on display  
-  Press buttons -0- and -8- to select function "Read Measuring Value 
Block" and confirm entry with -Q- button. 
Read Measurin
g Value Block 
Q
Input displa
y group number 
XXX
    
Indicated on display  
-  Press buttons -0-, -6- and -2- to select "display group number 062" and 
confirm entry with -Q- button. 
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24-154
 Note: 
The engine control module converts the voltage readings from the angle sensors into percentages of 5 V and displays them as percentages. (A signal wire voltage of 5 V is equivalent to 100%.) Read Measuring Value Block 62  
1 
2 
3 
4
    
Indicated on display  
-  Check specified display values for electronic throttle potentiometer 
voltages. 
  
Display fields  
  
1   2   3   4  
Display Group 062: Electronic throttle potentiometer voltages  
Display  
xx %  
xx %   xx %   xx %  
Indicates  
Throttle valve angle  
(angle sensor 1)  Throttle valve angle  
(angle sensor 2)  Accelerator position  
sensor 1  Accelerator position  
sensor 2  
Work Range  
min.: 0 %  
max.: 100 %  min.: 0 %  
max.: 100 %  min.: 0 %  
max.: 100 %  min.: 0 %  
max.: 100 %  
Specified value  
3 - 93 %  
(Idle value: 8 - 18%)  97 - 3 %  
(Idle value: 80 - 90%)  12 - 97 %   4 - 49 %  -  Observe display fields 1 and 2. 
-  Slowly depress accelerator pedal to full throttle position.
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