Checking throttle valve potentiometer — VW

Special tools, testers and auxiliary items

Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
Test box V.A.G 1598/18
Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Adapter set V.A.G 1594
Current flow diagram

Functional check

Connect fault reader V.A.G 1551 (V.A.G 1552) and select engine electronics control unit (address word 01); carry out selection with ignition switched on.
=> Page
01-4

Rapid data transfer
HELP
Select function XX
Indicated on display:

Input 08 for "Read measured value block" function and confirm with Q.

Read measured value block
HELP
Input display group number XX
Indicated on display:

Enter 03 for "Display group number" and confirm with Q.

Read
measured value block 3
⇒
1
2
3
4
Indicated on display:
(1...4 = Display zones)

Note:

If something different is indicated on the display:

=> Fault reader operating instructions

Check throttle valve angle on idling speed stop, in display zone 3.
Specification: 5...19 <°
Slowly open throttle valve fully and observe angle displayed in display zone 3.
The figure must increase uniformly over
the complete range.
Check throttle valve angle at full throttle stop in display zone 3.
Specification: 85...101 <°
Press ⇒ key.
Input 06 for "End output" and confirm with Q.
Switch off ignition

Note:

The displayed figure is dependent on the tolerances of the throttle valve potentiometer and does not correspond to the actual opening angle.

If the figure does not increase uniformly:

Replace throttle valve potentiometer.

If the figure remains constant:

Continue check according to following table.

Display · Cause · Continuation of check
106 <° · Open circuit in wire 2 · Check wiring / => Page 24-53
Short to positive in wire 2
Open circuit in wire 3 · Check voltage supply =>Page 24-46
0 <° · Open circuit in wire 1
Short to earth in wire 2 · Check wiring =>Page 24-53

Checking voltage supply

Separate 3 pin connector to throttle valve potentiometer.
Connect multimeter to measure voltage at contacts 1+3 of connector.
Switch on ignition.
Specification: min. 4.5 V
Switch off ignition

If the specification is not obtained:

Connect test box V.A.G 1598/18 to control unit wiring loom.

Check wiring between test box and 3 pin connector for open circuit according to current flow diagram.
Contact 1+socket 41
Contact 3+socket 33
Wire resistance: Max. 1.5 ω
Check wiring at 3 pin connector for short to one another.
Contact 1+socket 33
Specification: ∞ω

If no wiring fault is detected:

Renew Motronic control unit (J220)
=> Page
24-9
, item
16
.

Checking wiring

Connect test box V.A.G 1598/18 to control unit wiring loom.

If the display shows constant 0 <°:

Check wire for short to earth.
Sockets 01+40
Specification: ∞ω

If the display shows constant 106 <°:

Switch on ignition.
Check wire for short to positive, to do this connect multimeter to measure voltage at test box sockets 01+40
Specification: 0 Volt
Switch off ignition

Continuation if voltage is present:

If voltage of about 5 V was present:

Separate 3 pin connector to throttle valve potentiometer.
Switch on ignition.

Check wiring at 3 pin connector contacts 1+2 for short to one another according to current flow diagram.
Specification: ∞ω

If the voltage was approx. battery voltage:

Check wire at 3 pin connector contact 1 for short to battery positive according to current flow diagram.

Continuation if no voltage is present:

Separate 3 pin connector to throttle valve potentiometer.
Check wiring between test box and 3 pin connector for open circuit according to current flow diagram.
Contact 2+socket 40
Wire resistance: Max. 1.5 ω

If no wiring fault is detected:

Replace throttle valve potentiometer.