Testing accelerator position sender -G79: Audi 1.9 TDI (1Z, AHU)

Accelerator position sender -G79 is located on the accelerator pedal. Its function is to tell the control unit what position the pedal is in.

Special tools, testers and auxiliary items

Hand multimeter V.A.G 1526 or V.A.G 1526 A
Fault reader V.A.G 1551 (or vehicle system tester V.A.G 1552) with cable V.A.G 1551/1
Adapter set V.A.G 1594 A
Test box V.A.G 1598/18

Connect fault reader V.A.G 1551 and select engine electronics control unit => Page
01-3
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Read measured value block, Display Group 002, engine not running=>Page
01-77
.

Read measured value block 2
⇒
0 rpm
0.0 %
0
1
0
18.4 5C
Indicated on display:

Check display in display zone 2 (accelerator pedal position).
Specification: 0.0 % (accelerator not depressed)

Check display in display zone 3.
Specification:
0 1 0 (accelerator not depressed)
0 0 0 (accelerator depressed)

Press accelerator pedal down slowly.

Read measured value block 2
⇒
0 rpm
100 %
0
0
0
18.4 5C
Indicated on display:

Specification: The value in display zone 2 should increase steadily to 100 % (accelerator fully depressed).

On vehicles with an automatic gearbox the kickdown switch pressure point must be distinctly felt before the full throttle stop position is reached.

If the specifications for the initial and/or final readouts are not obtained, adjust accelerator position sender -G79 => Page
23-18
.

If the display does not change or only changes irregularly:

Switch off ignition.

Disconnect connector for accelerator position sender -G79
=>Fitting locations overview, Page
23-6
.

Set hand-held multimeter V.A.G 1526 to resistance measuring range and connect to the following contacts on connector for accelerator position sender -G79 using test leads from V.A.G 1594 A:

Contacts · Accelerator · Specification
1 + 3 · Not depressed · 0.8 ... 1.4 kω
2 + 3 · Not depressed · 0.8 ... 1.4 kω
4 + 6 · Not depressed · 0.8 ... 1.2 kω
Depressed · ∞ ω
5 + 6 1) · Not depressed · ∞ ω
Fully depressed · 0.8 ... 1.2 kω

1)
Only on vehicles with automatic gearbox.

If the specifications are not obtained, renew accelerator position sender -G79.

Testing voltage supply

Set hand-held multimeter V.A.G 1526 to voltage measuring range (20 V direct current) and connect it to contacts 2 and 3 on connector.
Switch on ignition.
Specification: approx. 5 V

If the specification is attained:

Check the wiring.

Testing wiring

With the ignition switched off, connect test box V.A.G 1598/18 to connector for engine control unit=>Page
23-49
.
Remove storage compartment (shelf) on driver's side.

=> General body repairs; Repair group 70; Dash panel; Removing driver's side shelf
General body repairs
Dash panel
Removing driver's side shelf

Unplug connector for accelerator position sender -G79 (located in footwell on accelerator pedal).

Test for open circuit and short to positive or earth in the following wiring connections:

Connector / for -G79 / Contact · Test box V.A.G 1598/18 / / Socket
1 · 15
2 · 57
3 · 55
4 · 65
6 · 1, 24, 46
5 1) · 62

1)
Only on vehicles with automatic gearbox.

Rectify any open/short circuit as necessary.
If the wiring is okay, fit a new Diesel direct injection system control unit -J248=>Page
23-45
.