System of onboard diagnostics (OBD) - a principle of functioning and codes of malfunctions
Data on diagnostic devices
- Check of serviceability of functioning of components of systems of injection and emission control is performed with a universal digital meter (DMM) (see. Illustration). Using a digital meter is preferred for several reasons. First, on analogue devices it is rather difficult (sometimes impossible) to determine the result of readings with an accuracy of hundredths and thousandths of, while at inspection of the contours including in the structure electronic components, such accuracy takes on special significance. The second, no less important reason is the fact that the internal contour of a digital multimeter, has high enough impedance (internal resistance of the device is 10 milliohms). As the voltmeter is connected to a checked chain in parallel, accuracy of measurement is higher, the smaller parasitic current will flow through the device itself. This factor is not significant when measuring relatively high voltages (9 ÷ 12), but becomes the determining the diagnosis of issuing low voltage components, such as, for example, oxygen sensor, which refers to the measurement of a volt.
- The most useful tools for diagnosing car engine management systems are handheld readers scanner type (see. Illustration). Scanners are the first generation to read fault codes systems OBD-I. Before use, the reader should be checked for compliance with the model and year of manufacture of the car inspected. Some scanners are multi-functional, due to the possibility of changing the cartridge depending on model of the diagnosed car (Ford, GM, Chrysler, etc.), while others are linked to the requirements of regional authorities and are intended for use in certain areas of the world (Europe, Asia, the United States and etc.). In recent years, it is absolutely essential for the diagnosis of engine management systems of modern cars are such readers devices, such as hand-held scanners such as, for example, Actron Scantool or AutoXray XP240
General description of the OBD system
All are described in this manual models are equipped with on-board diagnostics (OBD).
The main element of the system is the onboard processor, more often called the electronic module of management of functioning of the power unit (PCM). PCM is the brain of the engine management system. Input data is input to the information from various sensors and other electronic components (circuit breakers, relays, etc.). Based on the analysis of information received from the sensor data and in accordance with laid down in the basic parameters of the processor memory, RSM develops commands on operation of various control relays and actuators, thereby effecting adjustment of the operating parameters of the engine and providing peak efficiency of its return at the minimum fuel consumption.
On the service components of engine management systems / emission control are subject to special warranty with extended validity period. Do not attempt to self-diagnose failures PCM or replace system components before the release dates of these obligations, - address to experts branded service stations company Nissan.
Information gauges Camshaft position sensor (CMP) - The sensor generates data signals, based on an analysis which determines the current phase of PCM timing and engine speed, using the information in the management of sequential injection and ignition of air-fuel mixture in the combustion chambers.
The sensor (s) of the crankshaft position (CKP) - In the latest models use two sensor TFR, whereas earlier models used only one such sensor. Incoming signals from sensors used PCM as a reference when determining the engine speed and TDC position of the piston of each cylinder. On the basis of information received PCM controls the sequence of the injection and ignition of air-fuel mixture in the combustion chambers. In systems OBD-II Raman signals generated by sensors are also used in the diagnosis of failure of the power unit. Sensor Engine Coolant Temperature (ECT) - On the basis of information received from the sensor PCM makes the necessary adjustments of the air-fuel mixture and ignition timing, and controls the operation of the system EGR. Temperature sensor EGR - from the sensor information is used in determining the intensity of the exhaust gas recirculation in the receive path of the engine. The fuel temperature sensor - RSM uses the information emitted by the sensor in the diagnosis of failure of system components. Intake air temperature (IAT) - RSM uses coming from the IAT sensor information when adjusting the parameters of injection, ignition timing systems and in the management of the operation of EGR. Knock sensor - The sensor is a piezoelectric element, which responds to changes in the intensity of the vibration of the engine. Based on the analysis of information coming from the PCM encoder performs correction ignition angle for timely elimination occurring in combustion chambers detonation air-fuel mixture with potentially premature wear of the internal components of the engine. The gauge of absolute pressure in the pipeline (IDA) (late models) - sensor monitors variations in the depth of the vacuum in the intake manifold, associated with changes in crankshaft speed and engine load, and converts the received information in the signal amplitude. Information from the sensors is used by the management in the diagnosis of engine failures. Meter air mass (MAF) - MAF sensor determines the volume-weighted parameters entering into the inlet duct air stream. As a sensitive element in the sensor uses a filament. PCM uses a supplied MAP sensor and IAT the information at thin adjustments of injection parameters. An oxygen sensor (lambda - probe) - The sensor produces a signal whose amplitude depends on the ratio of oxygen (O2) contained in exhaust gases of an engine and outside air. On the basis of information received from the sensor determines the parameters of the PCM air-fuel mixture, promptly carrying out its enrichment or depletion. The gauge-switch fluid pressure system hydrostrengthening wheel (PSP) - On the basis of input from the gauge-switch PSP information PCM enhances the idle speed (due to the operation of the valve IAC) to compensate for the increasing loads on the engine, linked to the operation of the steering hydraulic booster at fulfillment maneuvers. Throttle Position Sensor (TPS) - The sensor is located on the throttle body and is connected to the throttle shaft. The amplitude signal outputted TPS RSM determines the angle of the throttle opening (controlled by the driver from the accelerator pedal) and adjusts the fuel supply into the intake ports of the combustion chambers. Sensor failure or weakening of its fastening leads to faults of injection and infringements of stability of turns of idling. The vehicle speed sensor (VSS) - As its name implies, a sensor informs the processor of the current vehicle speed. Other controlled by RSM characteristics - In addition to the sensors listed above issued to PCM comes as further details about the functioning of various components and systems that determine the performance of the engine. Among others, systems and components, control the operation of which carries PCM include:
- The air conditioning system;
- Battery (output voltage);
- System EVAP;
- Ignition switch;
- The gauge-switch start authorization;
- The operation of the transmission control system.
Actuators Relays functioning clutch R / C - PCM carries off the compressor K / V during an intense acceleration.
The control lamp "Check up the engine" - PCM makes inclusion of the warning lamp in the event of failures of functioning of the engine management system. Relays operation of the cooling fans - PCM controls the operation of the cooling fan on the basis of the analysis of the signals from the coolant temperature sensor. Vacuum control solenoid valve EGR - PCM controls the degree of opening of the vacuum to the EGR valve through a special intermediate solenoid valve. Valve EGR - On later models PCM controls the flow of exhaust gas recirculation valve via an electronic EGR. The valve purge of a coal adsorber - This solenoid valve actuating team RSM performs a purge of a coal adsorber EVAP, bringing accumulated inside the fuel vapor into the intake tract of the engine. Solenoid valve of turns of fast idling - This valve is used on the latest models and serves to increase the idle speed during cold weather. In fact, the valve acts as the choke on carburettor models. Front Mount power unit - On some models, the PCM also controls the stiffness of the front engine mount, depending on vehicle speed. Minimization of vibration is done by selecting one of the two support units. Injector fuel injection - PCM provides individual inclusion of each of injectors according to the established order of ignition. In addition, the module controls the duration of opening of injectors, determines the width of the control pulse, measured in milliseconds, and the amount of fuel injected into the cylinder. For more information on the basis of the system of injection, replacement and service of injectors, refer to Chapter 7. Fuel pump relay - Relay control module is activated by turning the ignition switch to START / RUN. When the ignition switch is supplying power to the fuel pump, which provides a pressure rise in the path of the power supply system of the car. For more information on the location and operation of the relay, refer to Chapter 5 and 31. The valve of stabilization of turns of idling (IAC) - IAC valve carries the dosage amount of air bypassed bypassing the throttle valve when the latter is closed, or occupies the idle position. Valve opening and the formation of the resulting air flow controls the PCM. Oxygen sensor heater - The functioning of the device carries PCM. Heater produces a rapid warm-up l-probe to normal operating temperature. Power transistor - transistor provides signal amplification ignition produced by PCM and at the right time produces an instant chassis ground of the primary circuit of the ignition system, causing the secondary side of the generation of explosive signal output coil (s) directly to the spark plug. Solenoid valve control the operation of power - the later functioning of the management model of the valve power carries PCM through a special magnet. Module operation control knob (SCI) - SCI, being separate from the PCM control module receives information signals from various sensors, such as VSS, the sensor switch permits startup of the turbine shaft speed sensor, TPS, CMP, etc., and uses received data to determine when shift transmission AT, a desired pressure in the path and angular locking of the rotation.
Read fault codes
If any malfunction repeating successively in spirit trips, the PCM commands the switch mounted in the instrument panel of a control lamp "Check up the engine", also referred to as an indicator of failure. The lamp will continue to burn until the violation will not disappear and will not appear for three or more trips.
Control box with one LED
Turn on the ignition. Jumper contacts IGN and CHK connector and 2 seconds later. remove the jumper. Consider flash lamp. The number of long flashes corresponding to the number of dozens of code, the number of short - the number of units. If you want to clear the memory again peremknite above contacts and 2 seconds later. remove the jumper. Switch off the ignition.
Location diagnostic socket. To read these codes Jumper contacts.
The control unit with red and green LEDs
For reading fault codes via the diagnostic lamp, or a control lamp "Check up the engine" using the selector located on the side wall of the PCM.
For reading fault codes is necessary to provide access to the RSM for the purpose of the selector switch on the flashing codes via the diagnostic lamp / control lamp "Check up the engine". PCM should be removed from its support bracket (without disconnecting the wiring) and act in accordance with the instructions below.
- Turn the ignition (without starting the engine). The control lamp "Check up the engine" on the instrument panel must remain switched on, which confirms the granting it the power of the PCM and the condition of the lamp.
Violation of the procedure described below procedure can lead to occasional cleaning of the PCM memory!
- Using a screwdriver turn the selector on the side of the PCM to fully clockwise. We should start simultaneous flashing both LEDs - after three flashes, turn selector fully counter-clockwise;
- Closely monitor the operation of the diagnostic lamp. The red LED is used to highlight dozen DTC unit code green LED flashes. For example, the code 43 (chain TPS) will be as follows: four glimmer of red diode, then three flashes green. The absence of the identified violations of the system shows the flashing code 55 (see. Below the map fault codes);
- When you turn the ignition off after it in code reading system automatically cancels the search results and the preceding reading process must begin anew.
Starting automatically blocks access to the system of self-diagnostics.
- If you turn the selector fully counter-clockwise, under item 2) to make at the time when:
- 1st glimpse turn test mode lambda probe (both LEDs are lit). Start the engine. The system will self-test and in the absence of fault green LED flashes. The green LED lights up constantly - a mixture pereobednena. The green LED is not lit - a mixture pereobogaschena. The red LED lights up at the end of self-test.
2nd glimpse turn test mode control loop quality mix (green LED lights up, red is off). Start the engine. The system will self-test and in the absence of fault green LED flashes. The red LED lights up constantly - a mixture pereobednena. The red LED is not lit - a mixture pereobogaschena. The red LED blinks with zalenym - optimal mixture.
- 4th glimpse turn test mode circuit throttle position sensor / vehicle speed (red LED). Start the engine. Red LED should turn ON and OFF each time you press the gas pedal. When driving the green LED should light up when speed exceeds 19 km / h.
- 5th glimpse of the dynamic test mode starts. Start the engine and changing the pace, watch for diodes.
- One flash of red - a fault in the crankshaft position sensor circuit;
- Two green flashes - a fault in the circuit of the air flow meter;
- Three flashes of red - a fault in the fuel pump circuit;
- Four green flashes - a fault in the circuit of the ignition system.
- Stop the engine.
Clear Memory ECM / PCM
Once identified in the diagnostic process violations are eliminated, it should be clear from the PCM memory recorded in her fault codes.
Clear memory by disconnecting the wires from the battery leads also to erase the basic parameters and infringement of stability of turns of idling for the first time after starting the engine.
- Think of memory recorded in the system error codes.
- Wait at least two seconds, then turn the selector on the side of the PCM to fully clockwise, - LEDs should start flashing.
- After four glimpses diodes turn selector fully counter-clockwise.
- Switch off the ignition.
List of self-diagnostic fault codes
Possible cause of failure
Malfunction in a chain engine speed sensor / crankshaft position sensor
Malfunction in a chain of air flow meter VAF / air mass MAF
Malfunction in a chain coolant temperature ECT
Malfunction in a chain of the vehicle speed sensor VSS
Malfunction in a chain ignition signal
A fault in the fuel pump circuit
Malfunction in a chain e / switch closed throttle position
Malfunction in a chain e / switch completely open throttle position / position "P" "N" AT
Malfunction in a chain of the valve of additional air IAC
Malfunction in a chain of the turbocharger pressure sensor
Air-conditioning / absence of faults (models without air conditioning) / Infringement of serviceability of functioning of the PCM (engine GA16i, CA18DE)
A fault in the signal chain starter
Malfunction in a chain of the oxygen sensor
Malfunction in a chain knock sensor / throttle position sensor (engine SR20Di)
Malfunction in a chain temperature sensor EGR
Faulty sensor circuit intake air temperature IAT
Malfunction in a chain of the fuel temperature sensor
Malfunction in a chain of the throttle position sensor TPS
The absence of fault
Leaks in the injectors injection
The fault in the signal injection
A fault in the signal chain of automatic transmission AT
Absence of fault codes in the system memory
Diagnosis security systems
Produced by the SRS warning lamp on the dashboard or via the diagnostic lamp.
Models with a pyrotechnic seat-belt tensioner
With diagnostic lamp
With the ignition off Jumper pins 7 and 11 of the diagnostic socket via the lamp no more 3.3Vt. Turn on the ignition. If OK light goes out after about 6 seconds. If the light is blinking may damaged wiring devices and pyrotechnic belt tensioners control unit.
According to the SRS warning lamp
With the ignition off, open the driver's door and turn on the ignition. Make sure that the lamp is lit and within 7 seconds 5 Press the switch the driver's door. After 2 seconds after the lamp goes out it will begin issuing blinking codes.
Possible cause of failure
Damage to the front impact sensor wiring. The block of management SRS
Damage to the wiring of driver airbag. The block of management SRS
Damage to the front impact sensor wiring. The block of management SRS
Damage to the wiring of the control unit of the system of safety SRS
Damage to the wiring of passenger airbag. The block of management SRS
Multiple defects in the wiring of the control unit, a shock sensor, airbag
Diagnosis of anti-lock brakes
Start the engine and drive the vehicle at a speed of 30 km / hour for at least 1 minute. Switch off the ignition and lock pin 4 of the diagnostic socket on the housing. Turn on the ignition and read codes for outbreaks control lamp ABS. Do not press the brake pedal during testing.
Possible cause of failure
Start issuing codes.
Rotor wheel speed sensor.
Open circuit speed sensor right front wheel.
Short circuit speed sensor right front wheel.
Open circuit speed sensor left front wheel.
Short circuit speed sensor left front wheel.
Open circuit speed sensor right rear wheel.
Short circuit speed sensor right rear wheel.
Open circuit speed sensor rear left wheel.
Short circuit speed sensor rear left wheel.
Output e / the magnetic valve of the right front wheel.
Input e / the magnetic valve of the right front wheel.
Output e / the magnetic valve of the left front wheel.
Input e / the magnetic valve of the left front wheel.
Output e / the magnetic valve of the right rear wheel.
Input e / the magnetic valve of the right rear wheel.
Output e / the magnetic valve of the left rear wheel.
Input e / the magnetic valve of the left rear wheel.
Low supply voltage.
Relay / hydraulic pump.
The electronic control unit.