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Idling compensation

Idling compensation



D/R input

Pin 42 of the MOTRONIC control module is supplied with information on the current gear position, P-N or R-D-1-2-3, from pin 11 of the automatic transmission's control module.

When any of the gear positions R-D-1-2 or 3 is selected, a supply of about 12 V is applied to pin 42 of the control module, which then attends to idling compensation.

Idling compensation is achieved by the control module opening the IAC valve by about 1.8 grammes per second above normal.

If no signal is received, idling speed will drop below 800 rpm when the DRIVE position is selected and then slowly rise to normal idling speed.

Secondary air injection pump

When the MOTRONIC control module grounds pin 26 and so starts the air pump, the IAC valve also opens at the same time for a mass air flow increase corresponding to about 0.9 grammes per second.

Input from AC/ACC

When the AC/ACC is activated, either manually via the AC switch or automatically via the ACC control module, a supply of about 12 V is applied to pin 40 of the MOTRONIC control module.

When the control module receives this voltage signal on pin 40 it increases idling speed before the compressor starts, which is accomplished by the control module grounding pin 25 at the same time as relay 156 is grounded through the pressure monitor.

If the signal is absent, the AC compressor will not start.

A delay and engine speed compensation are built into the control module.

Idling compensation is achieved by the control module opening the IAC valve so that the mass air flow increases by about 1.4 grammes per second above normal.

The control module always gives priority to the engine's need for maximum power so that at full throttle, such as when overtaking, the compressor is disconnected for the length of time that maximum power is required, but not for longer than eight seconds at most.

Should the coolant temperature climb to 120°C (250°F), the compressor will also be stopped by ICE (the control module for overriding electronic functions) breaking the connection to the anti-freeze thermostat.