Contents: On vehicles with a 68-pin control…↓ On vehicles with a 121-pin control…↓ On vehicles with a 68-pin control…↓ On vehicles with a 121-pin control…↓
1. Connect the VAG 1551 tester and, by entering "01" "Engine electronics", select the engine control unit. The engine should be idling. The display should show the following information:
- Fast data exchange HELP
- Dial function XX
2. Press "08" to select the "Read Block of Measured Values" function and confirm with the "Q" button. The display should show the following information:
- Reading the HELF block of measured values
- Enter group number XX
3. Press "007" to select the "Display Group 007" function and press "Q". The display should show the following information:
- Reading measured value block 7 →
- 15.4°C 15.9°C 16.7°C
4. If field 3 does not display actual information or is replaced with a temperature of 136.8°C, check the sensor and the wires going to it. Click "→".
5. Press "06" to select the "Quick Data Exchange" function and confirm by pressing the "Q" button.
6. Turn off the ignition.
On vehicles with a 68-pin control unit connector
7. Disconnect the wiring connector from the sensor (figure 3.57). Measure the resistance between the sensor contacts.
Figure 3.57. Disconnect the wiring connector from the sensor and measure the resistance between the sensor contacts.
On vehicles with a 121-pin control unit connector
8. Disconnect the wiring connector from the sensor (figure 3.58). Measure the resistance between contacts 1 and 2 of the sensor.
Figure 3.58. On vehicles with a 121-pin control unit connector: disconnect the wiring connector from the sensor and measure the resistance between contacts 1 and 2 of the sensor.
9. The set resistance value is shown in the figure 3.55. Area A shows the resistance in the temperature range of 0-50°C, area B shows the resistance in the temperature range of 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.
10. If the specified value is not achieved, replace the sensor.
[The original text can be found at www.VWmanual.ru]
On vehicles with a 68-pin control unit connector
11. If the specified value is reached, connect the VAG 1598/18 tester to the engine control unit wiring harness. Check the wires between the tester and the connector for continuity: pin 1 + socket 64, pin 2 + socket 33 (figure 3.59).
Figure 3.59. On vehicles with a 68-pin control unit connector: checking the resistance between the contacts of the coolant temperature sensor connector.
Specified value: max 1.5 ohm.
12. Check the wires of the finger connector for short circuit. Set value: ∞ Ohm.
13. If no fault is found in the wires, then replace the engine control unit.
On vehicles with a 121-pin control unit connector
14. If the specified value is reached, connect the VAG 1598/31 tester to the engine control unit wiring harness. Check the wires between the tester and the 4-pin connector for continuity: pin 1 + socket 52, pin 2 + socket 73 (figure 3.60). Specified value: max 1.5 ohm.
Figure 3.60. On vehicles with a 121-pin control unit connector: checking the resistance between the contacts of the coolant temperature sensor connector.
15. Check the 4-pin connector wires for short circuit. Specified value: ∞ Ohm.
16. If no fault is found in the wires, then replace the engine control unit.
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