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Applications

System of onboard diagnostics (OBD) - a principle of functioning and codes of malfunctions

Data on diagnostic devices

1. 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.

2. 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

1. The air conditioning system;
2. ABS;
3. Battery (output voltage);
4. System EVAP;
5. Ignition switch;
6. The gauge-switch start authorization;
7. Earthing;
8. The operation of the transmission control system.

Actuators

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.

PERFORMANCE ORDER

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.

List of self-diagnostic fault codes

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.

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.