Mono-Jetronic, Mono-Motronic, Digifant, Motronic
The Mono-Jetronic system, unlike the Digifant system, has 2 different temperature sensors. The intake air temperature sensor is located on top of the valve injector, see above.
The temperature sensor for the injection system is available in both systems, it is located on top of the cooling system flange and measures the temperature of the coolant. The plug of this sensor is blue.
Checking the intake air temperature sensor
The resistance of the intake air temperature sensor depends on the temperature of the central injection system. Remove the temperature sensor and heat up or measure the resistance at different ambient temperatures.
Disconnect plug -4- for intake air temperature sensor, see figure 24-281 above.
Measure the resistance at different temperatures at both outer contacts of the plug. The prescribed resistance values must match the prescribed values for the injection system temperature sensor, see diagram.
Checking the temperature sensor of the injection system
Disconnect the blue plug of the injection system temperature sensor by first depressing the fixing metal clip. The temperature sensor is located at the coolant system flange at the front of the cylinder head.
Up to 7/91: measure the resistance between both contacts of the temperature sensor.
From 8/91: The temperature sensor has a 4-pin connector. Measure the resistance between the two left-hand, looking in the direction of the flange, contacts of the temperature sensor. The temperature gauge on the instrument panel is connected to the two right contacts of the sensor.
Start the engine and warm up. Measure the resistance at various coolant temperatures and compare the obtained values with the values shown in the diagram. The temperature sensor can also be removed and heated in a bath of water for testing.
If the measured resistance values do not correspond to the prescribed values, unscrew the temperature sensor and replace it. When installing a new sensor, be sure to install the O-ring.
Connect the plug connector and secure with a metal clip.
If necessary, erase the fault codes in the memory device.
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