Throttle Valve Potentiometer, Checking

Checking Throttle Valve Potentiometer

Test sequence
- Connect VAG 1551 Scan Tool ((VAG 1552). Then switch ignition on and select engine control module with the "Address word" 01. (Connecting scan tool and selecting engine control module [1][2][3]Connecting VAG Scan Tool 1551/1552).

Indicated on display

Rapid data transfer HELP
Select function XX

- Press keys 0 and 8 for function "Read Measuring Value Block" and confirm entry with Q key.

Indicated on display

Read Measuring Value Block HELP
Input display group number XXX

- Press keys 0, 5 and 4 for "Display group number 54" and confirm entry with Q key.

Indicated on display: (1 to 4 Display zones)

Read Measuring Value Block 54 ->
1 2 3 4

- Read off throttle valve angle in display zone 3.
Throttle valve in start position: 0 to 6 angle degree
- Slowly open throttle valve slowly until fully open and observe angle display in display zone 3. Figure must increase uniformly overcomplete range up to a: min. 75.
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.

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 control module -J338-.

If the display constantly shows 0 angle degree or is above 90 angle degrees:
Display Cause
0 angle degree Open circuit or short to positive
above 90 angle degree Short to Ground

Continuation of check when display 0 angle degree:







- Pull 8 pin connector off throttle valve control module.
- Bridge connector contacts 5+7 with auxiliary cables from VAG 1594 and observe display.

If display jumps above 90 angle degree:
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.
- Replace throttle valve control module -J338-.

If display remains at 0 angle degree:
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.
- Check voltage supply of throttle valve control module and wiring to control module.

If the voltage supply and wiring is OK:
- Replace engine control module.

Continuation of check when display is above 90 angle degree:







- Pull 8 pin connector off throttle valve control module.

If display jumps to 0 angle degree:
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.
- Replace throttle valve control module -J338-.

If display remains above 90 angle degree:
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.
- Check voltage supply of throttle valve control module and wiring to control module.

If the voltage supply and wiring is OK:
- Replace engine control module.

Checking voltage supply and wiring to control module







- Pull 8 pin connector off throttle valve control module.
- Connect multimeter to measure voltage at connector contacts 4+7.
- Switch ignition on.
Specification: min. 4.5 V
- Connect multimeter to measure voltage at connector contacts 3+7.
Specification: at least 9 V
- Switch ignition off.

If the specifications are not attained:







- Connect test box VAG 1598/22 to control module wiring harness.







- Check wiring for open circuit between test box and connector using wiring diagram:
Contact 1 + socket 66
Contact 2 + socket 59
Contact 3 + socket 69
Contact 4 + socket 62
Contact 5 + socket 75
Contact 7 + socket 67
Contact 8 + socket 74
Wire resistance: max. 1.5 Ohm
- Check additional wires for short to one another.
Specification: Infinite Ohm

If no wiring malfunction is detected:
- Check engine control module voltage supply. Voltage Supply For Engine Control Module (ECM), Checking