Simos injection control system components (Audi A4 B5)

Table of contents: Mass Air Flow Sensor (MAF) ↓ Throttle position sensor (TPS,… ↓ Intake Air Temperature Sensor ↓ Vehicle speed sensor ↓ Coolant temperature sensor ↓ Engine speed sensor ↓ Throttle body ↓ Fuel injectors and fuel rail ↓ Fuel pressure regulator ↓ Hall sensor ↓ Oxygen sensor (Lambda probe) ↓ Electronic control unit (ECU) ↓

Note: Before starting work, read the warnings contained in paragraph 1. The ignition must be off at all times.

Mass Air Flow Sensor (MAF)

Removal

1. Disconnect the ground wire from the battery - see chapter 5A. If necessary, remove the top engine cover.

2. As described in paragraph 2, loosen the clamps and disconnect the air duct from the sensor, at the rear of the air filter housing.

3. Disconnect the wiring connector from the sensor.

4. Loosen the mounting screws and remove the sensor from the air filter housing. Remove the sealing ring.

Warning: Handle the sensor with care - internal components are easily damaged.

Installation

5. Installation - reverse procedure. Replace damaged O-ring.

Throttle position sensor (TPS, throttle potentiometer)

6. TPS is a component of the throttle body. Refer to the corresponding subparagraph.

Intake Air Temperature Sensor

Removal

7. The sensor is installed on the left side of the intake manifold.

8. Disconnect the wiring from the sensor.

9. Unscrew the sensor from the intake manifold. Remove the sealing ring.

Installation

10. Installation is the reverse procedure. Install a new sealing ring and tighten the sensor securely.

Vehicle speed sensor

11. The sensor is installed in the gearbox - refer to the description chapter 7A.

Coolant temperature sensor

Removal

12. The sensor is installed in the outlet flange of the cooling system at the rear of the cylinder head. Remove the upper engine cover if necessary.

13. Disconnect the wiring from the sensor.

14. Drain about a quarter of the coolant from the engine - see chapter 1A.

15. Remove the retainer and remove the sensor from the flange - be prepared for liquid spillage. Remove the sealing ring.

Installation

16. Installation - reverse procedure. Use a new sealing ring. Top up the coolant - see chapter 1A.

Engine speed sensor

Removal

17. The sensor is installed in the rear left part of the cylinder block, closer to the mating plane with the bell, behind the oil filter. If necessary, drain the engine oil and remove the oil filter with the oil cooler, as described in chapter 1A, to improve access.

18. Disconnect the electrical connector from the sensor.

19. Loosen the mounting bolt and remove the sensor from the cylinder block.

Installation

20. Installation - reverse procedure.

Throttle body

21. Disconnect the accelerator cable from the throttle control lever as described in paragraph 4.

22. Loosen the clamps and disconnect the intake air duct from the throttle body.

23. Disconnect the wiring connector from the TPS housing.

24. Disconnect the vacuum hose from the throttle body inlet and, if necessary, free the wiring from its fasteners.

25. As described in chapter 3, drain about a quarter of the coolant from the engine. Loosen the clamps and disconnect the cooling hoses from the fittings on the throttle body, remembering their correct connection.

26. Disconnect the purge vacuum hose from the throttle body fitting.

27. Remove the bolts and throttle body from the intake manifold. Remove and discard the gasket.

Installation

28. Installation - reverse procedure, please note the following:

a) Install a new gasket between the housing and the intake manifold.
b) When tightening the throttle body mounting bolts, tighten them to the specified torque.
c) Make sure that the vacuum hoses and electrical connectors are securely connected.
d) As described in chapter 1A, finish drinking the coolant.
c) If necessary, adjust the accelerator cable.

Fuel injectors and fuel rail

Removal

29. Disconnect the ground wire from the battery - see chapter 5A. If necessary, remove the top engine cover.

30. Disconnect the vacuum hose from the fuel pressure regulator on the fuel rail.

31. Remove the fuel tank filler cap and reinstall it to relieve any pressure in the tank.

32. Place a rag around the connection of the fuel supply line to the fuel rail. Also place a suitable container underneath to collect the fuel. Unscrew the connection nut, holding the bolt with another open-end wrench, and drain the fuel into the container underneath. Remove the rag.

33. Unscrew the return line connection and disconnect its tube from the ramp.

34. Disconnect the wiring from all injectors. Put tags on the wiring to avoid confusion during installation.

35. Loosen the mounting bolts, then carefully remove the fuel rail together with the injectors from the intake manifold.

36. After installing the unit on the workbench, tighten the fasteners and remove the injectors from the fuel rail. Remove the sealing rings.

Installation

37. Installation - reverse procedure. Please note the following.

a) Replace the injector sealing rings with new ones; before installation, lightly lubricate them with engine oil to facilitate installation.
b) Make sure the injectors are securely fastened.
c) Connect the fuel lines correctly. Check the condition of the sealing washers and replace them if necessary.
d) Check the reliability of vacuum and electrical connections
d) Connect the battery - see chapter 5A.
e) Finally, start the engine and check for leaks.

Fuel pressure regulator

Removal

38. If necessary, remove the top engine cover and relieve the pressure in the fuel system - see paragraph 9.

39. Disconnect the vacuum hose from the pressure regulator.

40. Place a rag under the regulator to collect fuel.

41. Pull out the spring retainer and remove the regulator from the fuel rail. Remove the sealing rings.

Installation

42. Installation - reverse procedure, install new sealing rings.

Hall sensor

Removal

43. Remove the camshaft sprocket as described in chapter 2A.

44. Remember the installation method of the sensor and mark its position relative to the cylinder head. Disconnect the wiring from the sensor.

45. Remove the rear timing belt cover from the cylinder head.

46. Loosen the remaining bolts and remove the sensor from the cylinder head.

Installation

47. Installation - reverse procedure. Before tightening the mounting bolts, center the sensor base plate.

Oxygen sensor (Lambda probe)

Removal

48. On all engines, the sensor is installed in the exhaust manifold to the right of the engine.

49. The sensor wiring connector is located on the left side of the engine shield, under the expansion tank of the cooling system.

50. Loosen the tank mounting screws and disconnect the wiring, move the tank to the side. Do not disconnect the hoses. Disconnect the sensor wiring from all fasteners.

51. Unscrew the sensor and remove it without damaging the tip.

Application: If there is a special head with a slot, when unscrewing the wire from the sensor, it is not necessary to disconnect it.

Installation

52. Apply non-stick lubricant to the threads, but do not coat the sensor tip with it.

Note: A new sensor may already have grease applied to its threads.

53. Screw in the sensor and tighten it to the specified torque.

54. Connect the wiring and secure it with plastic ties.

Electronic control unit (ECU)

Warning: Before disconnecting the connector, wait at least 30 seconds after switching off the ignition. When disconnecting the connector, all set data is erased. However, possible fault codes are retained in the memory. After connecting the connector, it is necessary to program the basic settings, which requires specialized Audi/VAG equipment. When replacing the ECU, it is also necessary to enter the identification code of the new unit into the immobilizer memory. Contact your dealer for assistance.

Removal

55. The electronic control unit is installed on the engine shield in the rear part of the engine compartment. On right-hand drive models it is located on the right, on left-hand drive models it is located on the left.

56. Disconnect the ground cable from the battery as described in chapter 5A.

57. Loosen the screws and remove the cover (Fig. 4.60).

Note: On early left hand drive models there are holes in the cover panel in front of the windshield to access the mounting bolt, on later models there is no hole - the panel must be removed.

58. Use a screwdriver to release the spring clip and lift the ECU upwards.

59. Release the retainer and disconnect the wiring connector from the unit.