1. Front Oxygen Sensor:
Greater than 2V——— Lean (Idle 1.5-N20.N55; 2V-N52);
Equal to 2V———- Complete combustion;
Less than 2V——– Rich
2. Rear Oxygen Sensor:
Greater than 0.45V——— Rich;
Equal to 0.45V———- Complete combustion (generally 0.7V);
Less than 0.45V——– Lean
3. Intake Manifold Pressure Sensor:
With VALTRANIC: Absolute pressure 950mbar, relative pressure 50mbar; if the VVT system fails and enters emergency mode, the data will be at 350mbar.
Without VALTRANIC: Relative pressure 350mbar (N54 engine is a twin-turbo engine)
4. Throttle Position Sensor:
With VALTRANIC: 3%-5% (if less than 3%, it indicates a lean mixture; small trend towards throttle opening; greater than 5% generally indicates a dirty throttle that needs cleaning, or indicates a rich mixture with a tendency to open the throttle.)
Without VALTRANIC: 2%-3%, exceeding 3.5% generally indicates a dirty throttle that needs cleaning.
N52: 4°
With VALTRANIC: 7°;
Without VALTRANIC: 3°
V1+V2=5V
5. Accelerator Position Sensor:
V1=2V2
6. Oil Pressure: Greater than 2bar,
Disconnect the oil pressure sensor plug, reaching 6bar.
The oil level sensor must be installed on the vehicle for testing (do not just unplug the plug for convenience).
7. Water Temperature Sensor:
Cold engine 2000 ohms———-(4V)
Hot engine 300-400 ohms————(0.8V)
Changes linearly with temperature
8. Knock Sensor:
About 0.3V (generally 1.x volts, should not exceed 3 or 5 volts) (ignition timing is delayed, adjusted later)
9. Air Flow Meter:
4-cylinder: 8-9kg/h—————-(old cars 11-14 kg/h)
6-cylinder: 12-13 kg/h—————-(old cars 18-20 kg/h)
8-cylinder: 15-16 kg/h—————–(old cars 26-28 kg/h)
10. VANOS: (Under hot idle conditions)
Intake: 85° (or 80°)
Exhaust: -115° (or 120°)
Note: Adjustments are made continuously during starting, cold engine, and load changes.
11. VALTRANIC Eccentric Shaft Position:
Mainly observe whether the position sensor changes sensitively and if there are any sticking phenomena.
At the moment of starting, the valves should open to the maximum for better starting; at this time, the current of the VALTRANIC motor will suddenly increase significantly.
VALTRANIC second generation: Valve lift range: 0.18-9.9mm
30°/30° (1° difference) (generally 26°)
Minimum valve lift calibrated: 0.95mm?
Valve lift: 0.95mm?
If there are issues: (ignition timing is delayed, adjusted later)
12. Calibration Values:
Additive calibration (idle): 0.5mg/cycle (positive indicates lean, negative indicates rich)
The standard value for the mixture additive calibration is 1 ～ 1.14; if the mixture additive calibration λ < 1, it indicates that the vehicle’s mixture is too rich.
Influencing factors: Secondary air injection
Multiplicative calibration (under load): 7.0% (positive indicates lean, negative indicates rich)
If all show lean, the reasons may include:
Low fuel pressure
Intake system leaks
Oxygen sensor
Air flow
13. Stability Value = Standard RPM (700) – Actual RPM
If greater than 0: indicates that the cylinder is not working well
If less than 0: indicates that the cylinder is working well
The sum of the stability values of all cylinders should equal 0 to be acceptable.
14. Intake Pressure Sensor:
Idle voltage: 1.13V
Rapid acceleration voltage: 3.39V
15. Injection Time: Ordinary engine: generally around 2.3ms
Direct injection engine: 1.18ms
16. Air-Fuel Ratio = 14.7kg air/1kg gasoline (complete combustion) = 14.7
& greater than 14.7: mixture is too lean
& equal to 14.7: just complete combustion
& less than 14.7: mixture is too rich
17. Excess Air Coefficient = Actual Air-Fuel Ratio / Theoretical Air-Fuel Ratio
λ greater than 1: mixture is too lean
λ equal to 1: just complete combustion (around 1.1)
λ less than 1: mixture is too rich
18. Fuel Pressure:
Low pressure: 6bar (N20, N55) 5bar (N52), 3.5 (N46)
High pressure: 50bar, maximum 200bar
19. Load Signal: 8.6%, opening the oil cap will decrease the value.
20. Ignition Timing: 6°
If the VVT system fails and enters emergency mode, the ignition timing will definitely be delayed, resulting in slower acceleration response.
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