E30 series BMW 3

since 1983-1994 of release

Repair and car operation

+ 1. Maintenance instruction
+ 2. Maintenance
+ 3. Engine
+ 4. Cooling system
+ 5. Heating and ventilation
+ 6. Fuel system
- 7. Exhaust system
   + 7.1.2. Exhaust system of cars 318i
   - 7.2. System of decrease in toxicity of exhaust gases
      7.2.2. Self-diagnostics of system of injection of Motronic
      7.2.3. Processor block (ECU block)
      7.2.4. Sensors of system of automatic control of the engine
      7.2.5. System of compulsory ventilation of a case (PCV system)
      7.2.6. Catching system паров gasoline (EVAP system)
      7.2.7. Catalytic converter
+ 8. Transmissions
+ 9. Coupling
+ 10. Brake system
+ 11. Running gear
+ 12. Body
+ 13. Electric equipment
+ 14. Good advice


7.2.4. Sensors of system of automatic control of the engine


The sensor of temperature of cooling liquid

The sensor of temperature of cooling liquid (shooter), tension from which moves on the processor block, is located near the sensor of the index of temperature, about a regulator of pressure of fuel.

The sensor represents a termistor (the resistor which size of resistance depends on temperature). In process of reduction of temperature of the sensor its resistance increases and on the contrary.


1. For sensor check, disconnect the socket and measure resistance of the sensor. On the cold engine resistance should be from 2 to 3 kiloohms. Start the engine and warm up – resistance of the sensor should become 200–400 Ohm.


If access to the sensor is complicated, remove the sensor and measure resistance, having placed it in a vessel with warm water.

2. To remove the sensor, wring out latches, disconnect the socket and accurately turn out the sensor. It is recommended to merge at first from cooling system a little liquid.
3. Installation is carried out upside-down. Slightly grease a sensor carving with hermetic.

The sensor of concentration of oxygen in exhaust gases

The sensor of oxygen of oxygen is established in cars with catalytic converter. The sensor will screw in a forward exhaust pipe after a final collector.

Socket of the sensor of oxygen
The socket of the sensor of oxygen on models 318i of the beginning of 1984 is located on the left side of the battery. On models of the second half 1984 and 1985 the sensor settles down in the same place.

The socket of the sensor of oxygen on models of 325i 1986-88.

The sensor traces the content of oxygen in exhaust gases and generates target tension from 0,1 In (the high content of the oxygen, the grown poor mix) to 0,9 In (the small content of the oxygen, the enriched mix). Changing target tension from sensors moves on the electronic control unit which defines an oxygen and fuel ratio in gas mixture. The control unit regulates an air / fuel ratio in a mix by a task of time of an open condition of nozzles. At a ratio of 14,7 parts of air to 1 part of fuel in an initial mix the content of harmful substances in exhaust gases minimum, at such ratio converter clears gases with maximum efficiency. The electronic control unit together with the sensor of oxygen provide maintenance of composition of gas mixture just at the specified level.

Relay of a heater of the sensor of oxygen

If the temperature of the sensor of concentration of oxygen is lower than normal working temperature, i.e. 320 ° With, tension on the sensor is absent. Therefore, until then while the engine will not get warm, on the electronic control unit of a signal from the sensor of oxygen does not arrive and the block works in a mode of the opened cycle (preparing gas mixture automatically).

If after engine warming up, or not less than 2 minutes of operation of the engine, tension later on the sensor not превышаеи 0,45 In at speed of rotation of the engine not less than 1500 rpm, the control unit brings a refusal code in memory.

If the sensor or its chain are faulty, the electronic control unit works in a mode of the opened cycle, i.e. the block doses out fuel according to the programmed value on its entrance, instead of according to a signal of the sensor of oxygen.

The correct operation of the sensor depends on the following conditions:

1. Electric: the low voltage generated by the sensor, very strongly depends on a condition of connections with wires.

2. Supply of external air: the sensor is arranged so that air circulates in its internal space. Every time at removal or installation be convinced of purity of air channels of the sensor.

3. Working temperature: signals from the sensor do not arrive on the electronic control unit until then while the temperature of the sensor will not reach about 300 ° Page. This factor should be considered at an assessment of serviceability of the sensor.

4. Qualities of gasoline: use of unleaded gasoline is an essential condition of the correct operation of the sensor. Fill the car with only unleaded gasoline.

Besides specified above conditions, at service of the sensor it is necessary to observe the following rules:

1. The flexible conductor and the socket of the sensor of oxygen are not folding and from the sensor are not disconnected. Damage or a separation of the flexible conductor or the socket can negatively affect serviceability of the sensor.

2. It is not allowed hits of dirt, lubricants and other extraneous components on the socket or on a tower insulator of the sensor.

3. It is forbidden to wipe the sensor all types of cleaners.

4. It is forbidden to drop the sensor or carelessly to address with it.

5. Watch correctness of installation of a silicone cover of the sensor to avoid cover melting because of which failure of the sensor is possible.

Types of the sockets applied to connection with the sensor of the content of oxygen and designation of conclusions (from conducting)

Purpose of conclusions on the sensor of the content of oxygen

Without heating (single-wire)
black wire (+)
Warmed up (3-wire)
conclusion 1 (+)
conclusions 3 (+) and 2 (+)
Warmed up (4-wire)
conclusion 2 (+)
conclusions 4 (+) and 3 (-)


1. Warm up the engine, disconnect the socket and check the digital voltmeter tension on a conclusion of a target signal of the sensor concerning weight. The sensor find on a big cover with a plait of black color in a back part of the engine.
2. At increase in turns tension from the sensor of oxygen should increase from 0,5 to 1,0. At reduction of turns tension decreases to 0–0,4 V.Esli a signal from the sensor of oxygen differs from the specified values, the sensor replace.
3. Check a heater of the sensor of oxygen (on a part of cars). On the specified conclusions there should be 12 V.Pri otsutstvii's tension of a food check the sensor relay.



When cooling the final collector or an exhaust pipe in which will screw the sensor, are compressed, therefore, on the cold engine to unscrew the sensor difficultly. Not to damage the sensor (it is supposed that you will use it further) start and warm up the engine within 1–2 minutes, stop the engine.

1. Disconnect the battery from weight.
2. Lift the car and establish on supports.
3. Accurately disconnect the socket from sensor conducting.
4. Carefully turn out the sensor.
5. At installation grease a sensor carving with structure against прихвата.

The sensor represents 2 pairs contacts. Idling which one pair is normally closed, and another – is opened. Near complete opening of a zaslonka the second pair of contacts becomes isolated. At the intermediate provision of a zaslonka both pairs contacts are opened. Break in chains or weakening of contacts of the sensor of a butterfly valve can cause spontaneous injection of fuel that is at the bottom of unstable operation of the engine idling.


1. The sensor of turn of a butterfly valve settles down at an end face of a shaft of a butterfly valve. Disconnect the socket and check resistance between pairs conclusions 2–18 and 3–18.
2. Between conclusions 2–18 should be a chain before zaslonka assignment on 0,2–0,6 mm from a closed position.
3. Between conclusions 3–18 should be a chain which remains when opening zaslonka to at 8-12 ° relatively completely open situation. If check yields negative result, adjust the sensor.
4. If the zaslonka is adjusted, check supply voltage 5 In on the sensor.


Release screws and having turned, establish the sensor in the necessary situation, tighten screws and check adjustment.

Measuring instrument of a stream of air

The order of removal and installation is described in subsection 6.4.

Sensors of system of ignition

The procedure for test, removals and installations is described in subsection