Functional check when pressing on accelerator

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When carrying out a functional check while pressing on the accelerator (quick and complete operation of the accelerator pedal module), the dynamic behavior of the air ratios is checked. Here, the air ratios are measured in a range from 1 to 32.

The air ratios behave as follows when the accelerator is pressed:

Operating the accelerator pedal module:
The engine acceleration and corresponding increase in fuel quantity lowers the air ratios.
Keeping the accelerator pedal module pressed:
Keeping the accelerator pedal module pressed (engine runs at maximum speed) stabilizes the air ratio at level considerably higher than the idle level.
Releasing the accelerator pedal module:
The fuel injection is switched off until the engine returns to idle speed. During this phase, the air ratios increase to a maximum value of 32.7 until the idle speed is reached and fuel injection is resumed.

The following graphic shows how the air ratios can behave when the accelerator is pressed.

NOTE: When exhaust-gas recirculation is switched off, the air ratios during the idle phase will be somewhat higher than those shown in this example.

Fig 1: Accelerator Pedal Module Signal Waveform

Courtesy of BMW OF NORTH AMERICA, INC.

Index	Explanation
1	Accelerator pedal module signal.
2	Engine speed.
3	Signal from oxygen sensor upstream of oxidation catalytic converter.
4	Signal from oxygen sensor downstream of oxidation catalytic converter.
5	Air ratios level during overrun fuel cut-off.
6	Air ratios level at maximum speed.
7	Air ratios level shortly after complete operation of the accelerator pedal module