Checking the temperature sensor (VW Passat B3)

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 at the top of the valve injector, see above.

The temperature sensor for the injection system is present 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 it up or measure the resistance at different ambient temperatures.

Disconnect plug "4" of the intake air temperature sensor, see above figure 24-281.

Measure the resistance at different temperatures on both outer contacts of the plug. The specified resistance values must correspond to the specified values for the injection temperature sensor, see diagram.

Checking the injection system temperature sensor

Disconnect the blue plug of the injection system temperature sensor, having first pressed the fixing metal bracket. The temperature sensor is located at the flange of the cooling system on the front side 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 contacts of the temperature sensor, when looking towards the flange. The temperature gauge on the instrument panel is connected to the two right contacts of the sensor.





Start the engine and warm it up. Measure the resistance at different 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 ones, unscrew the temperature sensor and replace it. When installing a new sensor, be sure to install the sealing ring.

Connect the plug connector and secure it with a metal bracket.

If necessary, erase the fault codes from the memory device.