Testing operation of the Lambda control: Audi 4.2 (AHK)
Step-by-step testing operation of the Lambda control for the Audi 4.2 (AHK): factory workshop text. What to remove, in what order, and what to check after.
Workshop procedure for AUDI — the factory write-up, straight from real workshop data.
🔧 Engine codes this applies to
📋 Procedure
Connect fault reader V.A.G 1551 (V.A.G 1552) and select control unit for engine electronics => Page
01-2
.
Read measured value block (function 08) and select display group 03 =>Page
01-88
).
Read measured value block 3
⇒
1
2
3
4
Readout on display:
Do not proceed with the test until the coolant temperature shown in display zone 3 has reached at least 80 oC.
Press the C key
Read measured value block (function 08) and select display group 11 =>Page
01-102
).
Read measured value block 11
⇒
1
2
3
4
Readout on display:
Display zone 3 will show the signal voltage for lambda probe 1.
Specification: -0.17 to 0.9 V
Display zone 4 will show the signal voltage for lambda probe 2.
Specification: -0.17 to 0.9 V
If the lambda probe voltage fluctuates very slowly, test the lambda probe heating => Page
24-51
.
If no probe voltage is displayed, there is an open circuit in the signal wiring; check the wiring => Page
24-54
.
If the display shows a constant voltage reading of -0.2...+0.2 V (mixture too lean), this means that the lambda control has reached the control stop in the "enrich" direction, but the lambda probe is still registering "Mixture too lean".
If the display shows a constant voltage reading of 0.7...0.9 V (mixture too rich), this means that the lambda control has reached the control stop in the "lean" direction but the lambda probe is still registering "Mixture too rich".
Press the C key
Read measured value block (function 08) and select display group 10.
Read measured value block 10
⇒
1
2
3
4
Readout on display:
The mixture learned values for idling appear in display zones 1 and 2.
Specified values for idling: -14...+9 %
The mixture learned values for part throttle appear in display zones 3 and 4.
Specified values for part throttle: -10...+10 %
If the readouts are less than the specifications, then the system has to constantly make the mixture significantly leaner.
If the specifications are exceeded, then the system has to constantly make the mixture significantly richer.
Causes for leaner mixture:
Only during idling: oil dilution caused by fuel
Idling and part throttle: fuel pressure too high
Note:
Oil dilution can be rectified by driving on the motorway or changing the oil.
Causes for richer mixture:
Only during idling: unmetered air in intake system.
Idling and part throttle: fuel pressure too low
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.
Ask about my car →Other AUDI procedures
- Testing injection quantity, leak tightness and spray pattern of injectors
- Testing fuel pump relay and actuation – Audi 4.2 AHK
- Testing lambda probe heating
- Removing and installing cylinder head, ABH, AEC
- Testing ignition coils
- Removing and installing toothed belt – Audi · 56 torque figures
- Removing engine – Audi A8 D3 · 41 torque figures
- Removing camshaft timing chain from camshafts – Audi A6/A7 C7 · 38 torque figures
- Installing engine – Audi A8 D4 · 36 torque figures
- Removing and installing camshaft timing chain · 29 torque figures
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.