Pic. 1.15. Control unit connector pin identification
- Before starting the diagnostic test, a preliminary check must be performed.
- The check can only be carried out if you know the operating principle of the fuel injection system.
- The diagnostic test should begin with an analysis of the symptoms of the malfunction.
Precautionary measures
- While the engine is running, do not disconnect the wires from the battery terminals or the connector from the control unit.
- Dry the car after painting at a temperature of no more than 80°C, and the drying time should not exceed 20 minutes.
- When disconnecting electrical connectors, be sure to check the condition of their contacts, latches and seals.
Preliminary checks
- Check the condition of the engine starting circuit: battery, power wires and starter.
- Check the fuel system: tightness of pipeline connections, cleanliness and correct installation of the fuel filter, as well as the presence of fuel in the fuel tank.
- Check the crankcase ventilation system hoses for contamination and pinching.
- Check the fuel hoses for contamination and kinks.
- Check the air supply system: the integrity and absence of damage to the air pipes, the tightness of the joints, the cleanliness of the air filter and the correct fit, as well as the reliability of tightening the clamps
- Check the accelerator cable adjustment: the smoothness of the cable movement and the complete opening of the throttle valve from the original position.
- Check the vacuum brake booster for leaks and the condition of the check valve.
- Make sure the engine's mechanical parts are in good condition, the valve timing is correct and the cylinder head gasket is tight.
- Check the condition of the exhaust system: the tightness of the elements and their connections.
- Check the condition and interelectrode gap of the spark plugs.
Attention. If, after completing the following checks, no malfunction is found, but symptoms are still present, replace the engine control module.
General power supply check
This check is as follows. to ensure the electrical supply to the fuel injection system, which must be carried out with the connector connected to the engine control unit.
Checking sensors, solenoid valves and wires
This check consists of checking the condition of the peripheral devices of the fuel injection system, which must be carried out with the connector connected to the engine control unit. When checking, all connectors of peripheral devices must be connected to them.
Checking fuel system sensors when there is no signal
This control consists of checking the supply voltage or signal of the sensors, which should be carried out with the connector connected to the engine control unit, the ignition is on and after a time delay or after cranking the engine. It is advisable to carry out the test with an adapter connected in series between the engine control unit and the connector.
Checking the fuel system power supply circuit
This control consists of checking the condition of various elements included in the fuel injection system.
Camshaft position sensor
The camshaft position sensor is located at the end of the camshaft and is secured to the cylinder head with three bolts (pic. 1.16). The sensor is located opposite a target with a 180°sector, mounted on the end of the camshaft. At the moment when the target sector passes in front of the sensor, the injection system control unit receives a 12 V signal from the sensor. When the target sector is not in front of the sensor, the injection system control unit receives a 0 V signal.
Pic. 1.16. Location of fuel injection system elements: 1 - coolant temperature sensor; 2 - camshaft position sensor; 3 - solenoid valve for idle speed control; 4 - throttle position potentiometer (not adjustable); 5 - air temperature sensor; 6 - absolute pressure sensor
Pic. 1.17. Oxygen sensor location (1)
The camshaft position sensor is powered by a voltage of 12 V. From the injection system control unit, a voltage of 5 V is supplied to the sensor via channel 2. Depending on the position of the target sector, the sensor interrupts the circuit and closes 5 V to «mass», while the injection system control unit receives a voltage of 0 V. or leaves the circuit open, while the injection system control unit receives a voltage of 12 V.