Checking accelerator pedal position sender (121-pin control unit) — VW
Checking accelerator pedal position sender (121-pin control unit) on VW: factory workshop procedure for engines AKU. Full factory text, tools and checks.
Workshop procedure for VW — the factory write-up, straight from real workshop data.
🔧 Engine codes this applies to
📐 26 workshop diagrams for AKU
Real factory drawings for this job — timing marks, bolt locations and routing. Locked in the free view.
📋 Procedure
Special tools, workshop equipment, test and measuring appliances and auxiliary items required
V.A.G 1526 Hand multimeter
V.A.G 1594 A Adapter set
V.A.G 1598/31 Test box
Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
Current flow diagram
Test sequence
Vehicles with right-hand drive
Vehicles with left-hand drive
=> Page
20-35
Test sequence
Connect fault reader V.A.G 1551 (V.A.G 1552) and with ignition switched on select engine electronics control unit with the "Address word" 01:
=> Repair group 01; Self-diagnosis; Connecting fault reader V.A.G 1551 and selecting engine electronics control unit
4-cyl. diesel engine Mechanics
Self-diagnosis
Connecting fault reader V.A.G 1551 and selecting engine electronics control unit
Rapid data transfer
HELP
Select function XXX
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 XXX
Indicated on display:
Press keys 0, 0 and 2 for "Display group number 2" and confirm entry with Q key.
Read measured value block 2
⇒
0 rpm
0.0 %
0 1 0
18.4 5C
Check accelerator pedal position display in display zone 2. The accelerator pedal must not be depressed.
Specification: 0.0 %
Check additionally the idling speed switch display in display zone 3. The centre position must show 1.
Display: 010
Read measured value block 2
⇒
0 rpm
100.0 %
0 0 0
18.4 5C
Depress accelerator pedal slowly until fully down, and observe display zones 2 and 3.
Display zone 2:
The accelerator pedal position figure must increase continuously.
Specification at full throttle position: 100.0 %
Display zone 3:
The centre position must change to 0.
Display: 000
End specification value not achieved:
Press the ⇒key.
Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
Switch off ignition.
Adjust accelerator pedal position sender
=>Page
20-38
Display does not change or is erratic:
Check accelerator pedal position sender as follows:
Press the ⇒key.
Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
Switch off ignition.
Remove cover in footwell (driver's side).
Disconnect 6-pin connector for accelerator pedal position sender.
Measure sender resistance between connector contacts 1+3.
Specification:
Accelerator pedal in idling position: 0.8...1.4 kω
Measure sender resistance between connector contacts 2+3.
Specification:
Accelerator pedal in idling position: 0.8...1.4 kω
Check idling speed switch (F60) in accelerator pedal position sender. To do this measure resistance between connector contacts 4+6.
Specification:
Accelerator pedal in idling position: 0.8...1.2 kω
Accelerator pedal depressed: ∞ ω
Measure sender resistance between connector contacts 5+6.
Specification:
Accelerator pedal in idling position: ∞ ω
Accelerator pedal depressed: 0.8...1.2 kω
If the specifications are not obtained:
Replace accelerator pedal position sender (G79)
=>Page
20-29
, item (2).
Interrogate fault memory:
=> Repair group 01; Fault memory; Interrogating fault memory
4-cyl. diesel engine Mechanics
Fault memory
Interrogating fault memory
If the specifications are obtained:
Remove wiper arms and cowl panel:
=> Electrical system; Repair group 92; windscreen wiper system; removing and installing windscreen wiper system
Electrical system windscreen wiper system removing and installing windscreen wiper system
Connect test box V.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.
Check wiring between test box and connector for open circuit according to current flow diagram.
Contact 1+ socket 69
Contact 2+ socket 12
Contact 3+ socket 50
Contact 4+ socket 70
Contact 5+ socket 63
Contact 6+ socket 51
Wire resistance: max. 1.5 ω
Additionally check wires for short to one another, to vehicle earth and to battery positive.
Specification: ∞ω
If no fault is detected in the wiring:
Renew Diesel direct injection system control unit (J248)
=> Repair group 23; Renewing engine control unit, coding and matching; Renewing engine control unit
4-cyl. diesel engine Mechanics
Renewing engine control unit, coding and matching
Renewing engine control unit
Vehicles with left-hand drive
Connect fault reader V.A.G 1551 (V.A.G 1552) and with ignition switched on select engine electronics control unit with the "Address word" 01:
=> Repair group 01; Self-diagnosis; Connecting fault reader V.A.G 1551 and selecting engine electronics control unit
4-cyl. diesel engine Mechanics
Self-diagnosis
Connecting fault reader V.A.G 1551 and selecting engine electronics control unit
Rapid data transfer
HELP
Select function XXX
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 XXX
Indicated on display:
Press keys 0, 0 and 2 for "Display group number 2" and confirm entry with Q key.
Read measured value block 2
⇒
0 rpm
0.0 %
0 1 0
18.4 5C
Check accelerator pedal position display in display zone 2. The accelerator pedal must not be depressed.
Specification: 0.0 %
In addition check the idling speed switch display in display zone 3. The centre position must show 1.
Display: 010
Read measured value block 2
⇒
0 rpm
100.0 %
0 0 0
18.4 5C
Depress accelerator pedal slowly until fully down, and observe display zones 2 and 3.
Display zone 2:
The accelerator pedal position figure must increase continuously.
Specification at full throttle position: 100.0 %
Display zone 3:
The centre position must change to 0.
Display: 0 0 0
End specification value not achieved:
Press the ⇒key.
Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
Switch off ignition.
Replace accelerator pedal position sender (G79)
=>Page
20-28
, item (3).
Interrogate fault memory:
=> Repair group 01; Fault memory; Interrogating fault memory
4-cyl. diesel engine Mechanics
Fault memory
Interrogating fault memory
Display does not change or is erratic:
Check accelerator pedal position sender wiring as follows:
Remove wiper arms and cowl panel:
=> Electrical system; Repair group 92; windscreen wiper system; removing and installing windscreen wiper system
Electrical system windscreen wiper system removing and installing windscreen wiper system
Connect test box V.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.
Remove cover in footwell (driver's side).
Disconnect 6-pin connector for accelerator pedal position sender.
Check wiring between test box and connector for open circuit using current flow diagram.
Contact 1+Socket 63
Contact 2+Socket 12
Contact 3+Socket 50
Contact 4+Socket 69
Contact 5+Socket 70
Contact 6+Socket 51
Wire resistance: max. 1.5 ω
Additionally check wires for short to one another, to vehicle earth and to battery positive.
Specification: ∞ω
If no fault is detected in the wiring:
Replace accelerator pedal position sender (G79)
=>Page
20-28
, item (3).
Interrogate fault memory:
=> Repair group 01; Fault memory; Interrogating fault memory
4-cyl. diesel engine Mechanics
Fault memory
Interrogating fault memory
TorqFix answers live for your specific car — tell it the engine code and it serves the matching sequence, torque figures and wiring for that exact variant.
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Who makes these pages, and how
TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.
The figures on this page come from manufacturer workshop documentation and are shown as they are. The page is assembled automatically from that data — it is not written by an AI. The AI works in the chat, where it answers for your specific car. It writes nothing here.
Variants of the same model differ. Cross-check torque against the factory manual for your engine before final tightening.
Seen a figure that does not match your manual? Write to us — we correct it and note when. support@torqfix.com
The story behind TorqFix → · How these pages are made →Workshop data on this page last updated 20 Sep 2026.