Checking slide travel potentiometer -G99 - engine codes ABP and AAT 1st control unit version — AUDI
Checking slide travel potentiometer -G99 - engine codes ABP and AAT 1st control unit version on Audi: factory workshop procedure for engines AAT, ABP.
Workshop procedure for AUDI — the factory write-up, straight from real workshop data.
📋 Procedure
ABP AEL
Note:
Engine control unit identification
=> from Page
01-5
.
Special tools and workshop equipment required
V.A.G 1526 A
V.A.G 1594 A
V.A.G 1598 with V.A.G 1598/5
VAS 5051 with VAS 5051/1 and VAS 5051/2
The slide travel potentiometer is responsible for feedback of the position of the modulating piston to the engine control unit, i.e. it determines the injection quantity.
Test sequence
Read measured value block, display group 000, engine idling
=> Page
01-60
.
Readout on VAS 5051:
Observe display in zone 7 (coolant temperature).
Specification: Less than 77 (corresponding to 80 °C)
Do not continue with test until coolant temperature has been attained.
Check display in zone -4-.
Specification: 5 ... 25
Terminate function "08 - Read measured value block" by touching ◂ key.
Touch "06 - End output".
Switch off ignition.
If reading does not match specification:
Replace injection pump => Page
23-18
.
If reading matches specification:
Checking internal resistance
Unplug connector from injection pump=>Exploded view of fitting locations -item
23-10
.
Connect up multimeter to measure resistance as follows.
Connector / Contact · Specification
1 + 3 · 0.5 ... 2.0 kω
2 + 3 · 1.0 ... 3.0 kω
If readings do not match specifications:
Replace injection pump => Page
23-18
.
If readings match specifications:
Checking power supply
Connect up multimeter for voltage measurement as follows.
Connector / Contact · Measure to
2 · Engine earth
Switch on ignition.
Specification: approx. 5 V
Switch off ignition.
If reading does not match specification:
Checking wiring
With ignition switched off, use adapter V.A.G 1598/5 to connect test box V.A.G 1598A to engine control unit connector only (not to control unit) => Page
23-45
.
Check for open circuit and short to earth/positive in the following wiring.
Connector / Contact · Test box V.A.G 1598 A / Socket
1 · 21
2 · 39
3 · 14
Check all wires for mutual short circuit.
Use current flow diagram to eliminate open circuit in wiring/short circuit.
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 →Workshop data on this page last updated 20 Sep 2026.