Page 1 of 37
24-88
 
     
Auxiliary input signals, 
checking 
     
Rear window defroster signal, checking
 
     
Requirement  
     
Engine Control Module (ECM) coding OK   
page 01
-247
 . 
     
Checking  
     
-  Using VAG 1551 scan tool, select "Read 
Measuring Value Block" function 08, display 
group 004, display field 4   page 01
-249
 . 
Read measuring value block 4 1 2 3 4
    
Indicated on display, note value in display field 4  
CAUTION! 
Do not use the shift inputs (identified by an X) during the RPM 
increase check. 
If display value is OK:     Specified value: 0XX_XX 
-  Switch ON rear window defroster.
   Specified value: 1XX_XX 
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        Page 4 of 37
24-90
      
A/C compressor shut-off signal, 
checking
 
     
Note:  
     The A/C compressor is switched off during 
acceleration by the Engine Control Module 
(ECM) and at wide open throttle by the 
Transmission Control Module (TCM) via the 
kickdown switch. 
     A/C compressor shut-off is bi-directional ("in"and 
"out"). 
     
IN: Shortly before switching the A/C 
compressor on, voltage is applied to the ECM 
which causes the Idle Air Control (IAC) valve to 
open a little more to adjust to the higher load. 
     OUT: When accelerating from a standstill 
position and at lower speed, the A/C 
compressor is shut off for approx. 12 seconds 
via control by the ECM. If the accelerator pedal 
is released early enough, the duration is 
reduced to a minimal 3 seconds. 
     
Checking requirements  
     A/C function OK 
     
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        Page 6 of 37
24-91
      
Checking  
     
-  Start engine and let idle. 
     
-  Switch A/C on, push "AUTO" button, set 
temperature to "LO" and blower speed to "HI". 
     
A/C compressor symbol must light up and 
A/C must run. 
     
-  Using VAG 1551 scan tool, select "Basic 
Setting" function 04, display group 004   page 01
-150
 . 
     
A/C compressor must stop (visual check) 
      If the A/C compressor does not shut off:  
     
-  Switch A/C off (press "minus" button for fresh air 
blower in A/C control head repeatedly, until all 
indicators are off). 
     
   Continue to let engine run in idle.
     
-  Using VAG 1551 scan tool, select "Read 
Measuring Value Block" function 08, display 
group 004. 
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        Page 12 of 37
24-94
      
Engine speed (RPM) signal, checking 
 
     
Notes:  
     The RPM signal is routed from the ECM to 
various electronic systems (e.g. automatic 
transmission, ABS, etc.). The RPM signal is 
monitored by the different electronic systems. 
      Carry out the following check only if the 
tachometer (in the instrument cluster) is 
inoperative, or if the A/C compressor is not 
running.  
     
-  Connect VAG 1367 engine-tester to tachometer 
using wiring diagram. 
     
-  Connect VAG 1367 engine-tester signal wire 
(green terminal) to instrument cluster RPM 
terminal and A/C control module RPM terminal 
(connector remains connected). 
     
-  Start engine and let idle.
     
RPM must be displayed again 
      If the specified value is obtained, the malfunction 
is in instrument cluster or on A/C control module.  
      If the RPM is not displayed on VAG 1367 engine-
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        Page 16 of 37
24-96
      
-  Switch Fluke 83 multimeter to voltage 
measurement range and connect between 
signal wire (trip computer 20-pin connector) and 
Ground (GND), using wiring diagram. 
     
-  Start engine and let idle. 
     
   Specified value: approx. 0.3 to 0.6 volts, 
corresponding to engine speed (RPM) 
     
-  Vary engine speed continuously from 1000 to 
4000 RPM. 
     
   Specified value: approx. 0.3 to 0.6 volts, 
corresponding to engine speed (RPM) 
      If the specified value is not obtained, even 
though the trip computer shows no consumption 
value or there is a stored malfunction in the 
TCM:  
     
-  Stop engine (switch ignition off).
     
-  Replace trip computer and/or TCM as 
required. 
      If the specified value is not obtained:  
    
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        Page 18 of 37
24-97
      
Vehicle speed signal, checking
 
     
Note:  
     The vehicle speed signal originates from the 
vehicle speed sensor (on the transmission) and 
is routed to the instrument cluster as well as to 
the Engine Control Module (ECM). 
     
Speedometer in instrument cluster OK 
     
Checking  
     
-  Using VAG 1551 scan tool, select "Read 
Measuring Value Block" function 08, display 
group 003   page 01
-249
 . 
Read measuring value block 3 1 2 3 4
    
Indicated on display  
-  Observe display field 4 while accelerating from standstill.
   Specified values: 
 
0 mph (at standstill) 
 Actual speed (vehicle driven)
- 
Press  button.
-  Select "End Output" function 06.
-  Press -Q- button to confirm input.
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        Page 21 of 37
24-99
      
Transmission Range (TR) selector lever 
position signal, checking
 
     
Note:  
     The Engine Control Module (ECM) uses this 
signal to recognize the transmission range 
selector lever position. When a driving mode is 
selected, idle speed should drop by approx. 50 
RPM to reduce creep. 
     
Checking requirement  
     
Control module coding OK   page 01
-247
 . 
     
-  Switch ignition ON.
     
-  Using VAG 1551 scan tool, select "Read 
Measuring Value Block" function 08, display 
group 004, display field 4   page 01
-249
 . 
Read measuring value block 4 1 2 3 4
    
Indicated on display  
CAUTION!     Specified value: XXX_1X (TR selector lever in P or N)
-  Apply brake and select drive mode (1, 2, 3, R or D).
   Specified value: XXX_0X 
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        Page 25 of 37
24-101
      
Shift procedure, checking
 
     
Notes:  
     
The Engine Control Module (ECM) uses this 
signal to briefly retard the ignition during shifting 
to reduce the mechanical jerking felt between 
shifts. 
     The shift signal is monitored by the 
Transmission Control Module (TCM). 
     
       Repair Manual, 5 Spd. Automatic 
Transmission 01V, Repair Group 01; On Board Diagnostic
   
      Carry out the following check only if a shift-
related DTC is stored in the TCM DTC memory.  
     
Checking requirement  
     
Control module coding OK   page 01
-247
 
     
CAUTION! 
     
Always use a second technician to operate 
the VAG 1551 scan tool while driving.  
     
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