Checking load signal potentiometer: VW 1.9 D (AEF)

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 1551/1
Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Adapter set V.A.G 1594
Current flow diagram

Test sequence

Connect the fault reader V.A.G 1551 (V.A.G 1552) and with ignition switched on select Diesel pump electronics control unit with the "Address word" 41.
(Connecting fault reader and selecting engine electronics control unit => Page
01-3
.)

Rapid data transfer
HELP
Select function XX
Indicated on display:

Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

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

Press keys 0 and 1 for "Display group number 01" and confirm entry with Q key.

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

Read off voltage value in display zone 2.
Specification: At least 0.2 V
Slowly open throttle to full throttle position and observe the voltage indicated in display zone 2. The voltage must increase uniformly over the whole range.
Specification: Max. 4.8 V
Press the ⇒key.
Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
Switch off ignition.

If the voltage does not increase uniformly:

Renew injection pump =>Page
23-14
.

If the voltage increases uniformly but is not within the specification limits:

Check governed speed =>Page
23-31
Check wire to load signal potentiometer between automatic glow period control unit (J179) and 3 pin connector for transfer resistances according to current flow diagram (control unit pulled off).
Wire resistance: Max. 1.5 ω

If no wiring fault is detected and the governed speed is OK:

Renew injection pump =>Page
23-14
.

If voltage remains constant:

Switch off ignition.
Unclip 3-pin connector -1- from retainer -3-.
Separate connector.

Connect multimeter to measure voltage at connector contacts 1+2.
Switch on ignition.
Specification: min. 4.9 V
Switch off ignition.
Check wire to load signal potentiometer between automatic glow period control unit (J179) and 3 pin connector for transfer resistances according to current flow diagram (control unit pulled off).
Wire resistance: Max. 1.5 ω
Additionally check wires for short to one another.
Specification: ∞ω

If the voltage supply and wiring is OK:

Renew injection pump =>Page
23-14
.

If no wiring fault is detected and a minimum voltage of 4.9 V was not present between contacts 1+2:

Renew automatic glow period control unit (J179) =>Page
23-4
, item
6
.