Diagnosis during cold start

P1561, P1562 

During cold start (catalyst heating) it is checked whether there is a permanent deviation between the current idle speed and the setpoint idle speed.

If the throttle valve opens too much it may happen that the idle speed rises above the fuel cut-off engine speed and the system starts oscillating. To cover this special case the number of detected fuel cut-offs during an idle phase is analyzed.

If

the deviation (positive) between setpoint and current idle speed (underspeed) exceeds a calibrated threshold and

integrator at upper limit and

the engine load lies below a calibrated threshold, all for a calibrated period of time a malfunction is detected and a minimum fault LLRKH is set.

If

the deviation (negative) between setpoint and current idle speed (overspeed) lies below a calibrated threshold and

integrator at lower limit and

still no fuel cut-off condition has been detected,

all for a calibrated period of time, a malfunction is detected and a maximum fault LLRKH is set.

If the number of detected fuel cut-offs during this idle phase exceeds a calibrated threshold for a calibrated period of time, a malfunction is detected and a maximum fault LLRKH is set.