Butterfly position sensor

For an error at the idle contact (short circuit or open circuit) the control unit implements two strategies according to the moment of recognition:

• recognition (open ciruict) when the ignition is switched to the ON position with no recovery value (unknown);
• recognition (short circuit or open circuit) with key in ON position, the control unit operates the direct current motor bringing it into the safety position (butterfly idling).

Butterfly position sensor

The emergency/safety function for the sensor is rendered operational when problems with the actual sensor do not allow the electronic control unit to detect the actual butterfly valve opening angle (α).

• with problems in track 1 of the sensor, a pre-defined safety injection time and an ignition advance are imposed and an idle adjustment motor emergency position;
• with problems in track 2 only a safety injection time and ignition advance are imposed.

Coolant temperature sensor

With the coolant temperature sensor disconnected, with a short circuit (c.c.) or an open circuit (c.a.), the signals reaching the control unit are implausible, i.e.:

• c.c. with coolant temperature > 128°C;
• c.a. with coolant temperature < -50°C;
• false contact when there are downward shifts in temperature which are too large between two successive samples;
• signal not plausibile if with the coolant temperature < +60°C, and the engine running the signal emitted by the sensor does not vary.

If the control unit detects one or more of the above signals, the recovery strategy should be implemented:

• with the air temperature < 24°C, the control unit considers the coolant temperature equal to the air temperature for around 4 minutes, after which it assumes a coolant temperature value equal to 100°C;
• with the air temperature ≥ 24°C, the control unit considers the coolant temperature equal to 100°C.

Air temperature sensor

With the air temperature sensor short circuited (c.c.) or with an open circuit (c.a.), the control unit receives signals which are implausible, i.e.:

• sensor in c.c. with air temperature > 128°C;
• sensor in c.a. with air temperature < -50°C.

In these cases the control unit implements the recovery strategy taking an air temperature of 20°C as a reference.

Lambda sensor

If the Lambda sensor is not working properly (open circuit or short circuit), the injection system operates in open loop, i.e. without correcting the injection times according to the sensor signal, therefore the Lambda mixture strength is equal to 1.