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Ignition system, glow plug system > < Air conditioning signals, two ways: verification

Leon Mk1

Inlet air temperature sender: verification
   
Inlet air temperature sender: verification
Special tools and workshop equipment required
t  Hand multimeter -V.A.G 1526 A- or multimeter -V.A.G 1715-
t  Fault reader -V.A.G 1551- or vehicle system tester -V.A.G 1552- with cable -V.A.G 1551/3B-
t  Auxiliary measuring set -V.A.G 1594 C-
t  Test box -V.A.G 1598/18-
t  Electric circuits flow diagram
t  Chilling spray (commercially available)

Checking process
–  Connect the equipment -V.A.G 1551- (-V.A.G. 1552-). Switch ignition ON and select engine control unit with the “Address code” 01. (Fault reader: Connecting and selecting the engine control unit → Chapter.)
   
Display indication:
–  Press the keys 0 and 8 for the function “Read measurement block values”, confirm using the key Q.
  
Rapid data transmission             HELP
Select the function XX
Display indication:
–  Press keys 0, 0 and 2 for “Display group number 2” and confirm entry with Q key.
  
Read measurement block values       HELP
Input the indication group number XX
Display indication:
(1…4 = Display fields)
–  Read intake air temperature value in display zone 4.
  
Read measurement value block         2->
         1         2         3         4
IndicationCauseContinuation of check
Approx. -55 °COpen circuit or short to positive → Anchor
Approx. 130 °C or moreShort circuit to earth → Anchor
Approx. Ambient temperature → Note— → Anchor

1)  If the indicated temperature varies significantly from the ambient temperature of the sender, first check the resistance values of the sender cables.
Continuation of the verification in the case where the indication is approx. -55°C
–  Remove the air inlet duct.
   
–  Extract the 4-pin connector -1- from the injection unit -2-.
–  Bridge the connections 1+4 from the connector using the auxiliary cables from -V.A.G 1594 C- and note the indication in the display.
Indication approx. 130 °C or more:
–  Replace support for injector with inlet air temperature sender -G42- → Item
Indication approx. -55 °C:
–  Press the key →.
–  Press keys 0 and 6 for the “End output” function and confirm input with the Q key.
–  Switch ignition off.
  N24-0273
–  Connect the tester -V.A.G 1598/18- to the control unit cable harness.
–  Check the cables between the test box and the 4-pin connector for an open circuit following the current circuits diagram.
  N24-0334
PinTest box -V.A.G 1598/18-, test box socket
443
Cable resistance: 1.5 Ω max.

–  Check also for short circuits to the battery positive.
   Specification: ∞ Ω
–  Check the cables between the test box and the 4-pin connector for an open circuit following the current circuits diagram.
   
PinTest box -V.A.G 1598/18-, test box socket
117
Cable resistance: 1.5 Ω max.

If no wiring fault is detected:
–  Replace the engine control -J257- → Item
Continuation of the verification in the case where the indication is approx. 130°C or more
–  Remove the air inlet duct.
   
–  Extract the 4-pin connector -1- from the injection unit -2-.
Indication approx. -55 °C:
–  Replace support for injector with inlet air temperature sender -G42- → Item
Indication approx. 130 °C or more:
–  Press the key →.
–  Press keys 0 and 6 for the “End output” function and confirm input with the Q key.
–  Switch ignition off.
–  Extract the connector from the engine control unit.
–  Check the cable between the control unit connector and the 4-pin connector, pin 4, for a short circuit with the cable pin 1 and the vehicle earth according to the electric current circuits diagram.
   Specification: ∞ Ω
If no wiring fault is detected:
–  Replace the engine control -J257- → Item
Continuation of the verification in the case where the indication is ambient temperature
–  Remove the air inlet duct.
  N24-0149
–  Apply the chilling spray -arrow-, noting the temperature value. The temperature value should fall.
–  Read and remember the intake air temperature value in display zone 4.
–  Press the key →.
–  Press keys 0 and 6 for the “End output” function and confirm input with the Q key.
  N24-0198

Ignition system, glow plug system > < Air conditioning signals, two ways: verification