Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
ME-SFI lambda control, function - GF07.61-P-4022AMG
ENGINE 156.980 in MODEL 164, 251 up to Model Year 8
ENGINE 156.982 in MODEL 209
ENGINE 156.983 in MODEL 211, 219
ENGINE 156.984 in MODEL 216, 221 up to Model Year 8
The mixture composition is controlled within the narrowest possible limits around λ = 1 in order to achieve a high conversion of exhaust gases (exhaust gas conversion) in catalytic converters.
The O 2 sensors upstream of TWC react to the oxygen share in the exhaust and transmits a corresponding voltage signal to the ME-SFI [ME] control unit. Consequently, the mixture composition is modified by control of the injection quantity, so that λ=1 is obtained. This process is repeated constantly (control loop).
The ME-SFI [ME] control unit alters the mixture composition with a time delay in order to prevent any risk of jerking.
Control of the air/fuel ratio is much faster by using a wideband oxygen sensor (continuous signal of λ 0.7 to 4.0) as O 2 sensors upstream of TWC.
The function of the lambda control (closed-loop operation) is dependent upon:
- Coolant temperature at start (dependent on the particular operating condition)
- Operating temperature of the O 2 sensors upstream of TWC
- Engine idling or partial-load range
- Deceleration fuel shutoff not active.
Exhaust gas conversion in the three way catalytic converter
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.