Checking the fuel temperature sensor

1. Connect the VAG 1551 tester and by typing «01» «Engine electronics», select the engine control unit. The engine must be running at idle. The display should show the following information:


2. Click «08» to select a function «Reading a block of measured values» and confirm by pressing the button «Q». The display should show the following information:


3. Click «007» to select a function «Group 007 display» and press «Q». The display should show the following information:


4. If field 1 does not display real information or it is replaced by a temperature of -5.4°C or -5.6°C, check the sensor and the wires going to it.


5. Click «→».

6. Click «06» to select a function «Output Completion» and confirm by pressing the button «Q».

7. Turn off the ignition.

On vehicles with a 68-pin control unit wiring connector

8. Disconnect the wiring connector from the sensor (connector for the fuel injection quantity adjustment mechanism on the injection pump) (pic. 6.87).

On vehicles with 80-pin control unit wiring connector

9. Disconnect the ten-pin wiring connector from the sensor (connector for the fuel injection quantity adjustment mechanism on the injection pump) (pic. 6.88).

For all vehicles

10. Measure the resistance between pins 4 and 7. The set value is shown in fig. 6.89. Area A shows resistance in the temperature range 0-50°C, area B shows resistance in the temperature range 50-100°C. For example, a temperature of 30°C corresponds to a resistance of 1500-2000 ohms; a temperature of 80°C corresponds to a resistance of 275-375 ohms.




11. If the specified value is not reached, replace the injection pump.

12. If the set value is reached:

On vehicles with a 68-pin control unit wiring connector

• Connect the VAG 1598/18 tester to the engine control unit wiring harness (rice. 6.54);
• Check the wire between the tester and the connector for an open circuit: pin 4 + socket 63, pin 7 + socket 33 (pic. 6.90). Set value: 1.5 ohm;
• Additionally, check the wires for shorting one to the other, to «mass» vehicle and to the positive pole of the battery. Specification resistance: ∞ Ohm;

On vehicles with 80-pin control unit wiring connector

• Connect the VAG 1598/22 tester to the engine control unit wiring harness (rice. 6.56);
• Check the wire between the tester and the connector for an open circuit: pin 4 and slot 76, pin 7 and slot 53 (pic. 6.91). Set value: 1.5 ohm;
• Additionally, check the wires for shorting one to the other, to «mass» vehicle and to the positive pole of the battery. Specification resistance: ∞ Ohm.

For all vehicles

13. If no fault is found in the wires, replace the engine control unit.