BMW 3 Series E30

since 1983-1994 release

Repair and operation of the car

+ 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. System of catching of vapors of gasoline (EVAP system)
      7.2.7. Catalytic converter
+ 8. Transmissions
+ 9. Coupling
+ 10. Brake system
+ 11. Running gear
+ 12. Body
+ 13. Electric equipment
+ 14. Useful tips


7.2.4. Sensors of system of automatic control of the engine


Sensor of temperature of cooling liquid

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

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


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


If access to the sensor is complicated, then remove the sensor and measure resistance, having placed it in a vessel with heated 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 the cooling system a little liquid.
3. Installation is carried out upside-down. Slightly grease a sensor carving with sealant.

The sensor of concentration of oxygen in exhaust gases

The sensor of oxygen of oxygen is installed in cars with catalytic converter. The sensor is screwed in a forward exhaust pipe after a final collector.

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

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

The sensor traces the content of oxygen in exhaust gases and generates output tension from 0,1 B (high content of oxygen, grown poor mix) to 0,9 B (small content of oxygen, enriched mix). The changing output tension from sensors moves on an electronic control unit which defines a ratio of oxygen and fuel in gas mixture. The control unit regulates a ratio of air/fuel in 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 initial mix the content of harmful substances in exhaust gases minimum, at such ratio converter purifies gases with maximum efficiency. An electronic control unit together with the sensor of oxygen provide maintenance of composition of gas mixture just at the specified level.

Oxygen sensor heater relay

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

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

If the sensor or its chain are faulty, then the electronic control unit works in the mode of the opened cycle, i.e. the block doses fuel according to the programmed value on its entrance, but not according to an oxygen sensor signal.

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

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

2. Supply of external air: 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 an electronic control unit until temperature of the sensor does not reach about 300 °C. This factor should be considered at 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 only with unleaded gasoline.

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

1. The flexible conductor and the socket of the sensor of oxygen are non-demountable and are not disconnected from the sensor. Damage or a separation of the flexible conductor or the socket can have an adverse effect on serviceability of the sensor.

2. Hit of dirt, lubricants and other foreign components on the socket or on the tower isolation center of the sensor is not allowed.

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

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

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

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

Purpose of conclusions on the sensor of 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 an output signal of the sensor concerning weight. Find the sensor 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 has to increase from 0,5 to 1,0. At reduction of turns tension decreases up to 0–0,4 Century. If the signal from the sensor of oxygen differs from the specified values, then replace the sensor.
3. Check an oxygen sensor heater (for parts of cars). On the specified conclusions there has to be tension of 12 Century. In the absence of food check the sensor relay.



When cooling the final collector or an exhaust pipe in which will screw the sensor contract therefore, on the cold engine it is difficult to unscrew the sensor. 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 conducting of the sensor.
4. Carefully turn out the sensor.
5. At installation grease a sensor carving with structure against a holding strap.

The sensor represents 2 couples of contacts. Idling one couple of which is normally closed, and another – is opened. Near full opening of the gate the second couple of contacts becomes isolated. At an intermediate position of the gate both couples of 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 the reason 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 couples conclusions 2-18 and 3-18.
2. Between conclusions 2–18 has to be a chain before assignment of the gate on 0,2–0,6 mm from a closed position.
3. Between conclusions 3–18 has to be a chain which remains when opening the gate to at 8-12 ° rather completely open situation. If check yields negative result, then adjust the sensor.
4. If the gate is adjusted, then check the supply voltage of 5 V on the sensor.


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

Air stream measuring instrument

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