Nissan Maxima QX

since 1993 release

Repair and operation of the car

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

Data on diagnostic units

Check of serviceability of functioning of components of systems of injection and decrease in toxicity of the fulfilled gases is made by means of the universal digital measuring instrument (multimeter). Use of the digital measuring instrument is preferable for several reasons. First, on analog devices it is rather difficult (sometimes, it is impossible), to define result of the indication to within the 100-th and thousand shares while at inspection of the contours including electronic components in the structure, such accuracy is of particular importance. The second, not less important, the fact that the internal contour of a digital multimeter, has rather high impedance is the reason (internal resistance of the device makes 10 million Ohms). As the voltmeter is connected to the checked chain in parallel, the accuracy of measurement of subjects is higher, than smaller parasitic current will pass through actually device. This factor is not essential at measurement of rather high values of tension (9 ÷ 12 V), however becomes defining at diagnostics of the elements giving low-voltage signals, such as, for example, oxygen sensor where it is about measurement of shares of volt.

The most convenient devices for diagnostics of control systems of the engine of modern models of cars are manual readers of skanerny type. Scanners of the first generation serve for reading of codes of malfunctions of the OBD-I systems. Before application the reader should be checked for compliance of model and year of release of the checked car. Some scanners are multipurpose, at the expense of a possibility of change of a cartridge depending on model of the diagnosed car (Ford, GM, Chrysler, etc.), others are tied to requirements of the regional authorities and intended for use in certain regions of the world (Europe, Asia, the USA, etc.).

With introduction to production to meeting requirements of the last legislations for environmental protection of system of onboard diagnostics of the second generation (OBD-II) readers of a special design began to be issued. Some producers marketed the scanners intended for use by amateur mechanics in house conditions, - ask in shops of automobile accessories.

Also the scanners of other type intended for reading from memory of the onboard processor by direct connection to the diagnostic socket of the main braid of an electrical wiring of the car are issued.

General description of the OBD system

All models described in the present manual are equipped with system of onboard diagnostics (OBD). On models 1993 and 1994 of of the issue the OBD-I system is applied, since 1995 all cars began to be completed with systems of diagnostics of the second generation (OBD-II).

Basic element of both systems is the onboard processor more often called by the electronic module of management of functioning of the power unit (RSM). RSM is a brain of a control system of the engine. Basic data arrive on the module from various information sensors and other electronic components (switches, the relay, etc.). On the basis of the analysis of the data arriving from information sensors and according to the basic parameters put in the processor memory, RSM develops commands for operation of various operating relays and actuation mechanisms, carrying out thereby adjustment of working parameters of the engine and providing maximum efficiency of its return at the minimum fuel consumption.

Special guarantee certificates with the extended validity extend to service of components of control systems of engine/decrease in toxicity of the fulfilled gases. It is not necessary to make attempts of independent performance of failure diagnostics of RSM or replacement of components of system, to an exit of terms of these obligations, - address specialists of company car repair shops of the Toyota company.

Information sensors

Sensor of position of the camshaft (SMR) - The sensor develops information signals on the basis of which analysis RSM defines the current phase of gas distribution and frequency of rotation of the engine, using the obtained information at management of the sequence of injection and ignition of air-fuel mix in combustion chambers.

Sensor(s) of provision of a bent shaft (ICR) - On all models since 1995 issues are used two sensors of ICR whereas on earlier models only one such sensor was used. The signals arriving from sensors are used by RSM as turns of the engine and provisions of VMT of the piston of each of cylinders, basic at definition. On the basis of the obtained information of RSM exercises control of the sequence of injection and ignition of air-fuel mix in combustion chambers. In the OBD-II systems the signals developed by sensors of ICR are used also at failure diagnostics of the power unit.

Sensor of temperature of cooling liquid of the engine (EST) - On the basis of information of RSM arriving from the sensor carries out necessary corrections of composition of air-fuel mix and a corner of an advancing of ignition, and also controls work of the EGR system.
EGR temperature sensor - Information arriving from the sensor is used when determining intensity of recirculation of the fulfilled gases to the reception highway of the engine.

The fuel temperature sensor - RSM uses information issued by the sensor at failure diagnostics of components of system.

The sensor of temperature of the soaked-up air (IAT) - RSM uses information arriving from the IAT sensor at adjustments of parameters of injection, installations of a corner of an advancing of ignition and at management of functioning of the EGR system.

The detonation sensor - the Sensor represents the piezoelement reacting to change of intensity of vibrations of the engine. On the basis of the analysis of information of RSM arriving from the sensor carries out corrections of a corner of an advancing of ignition for the purpose of timely elimination of the detonation of the air-fuel mix fraught with premature wear of internal components of the engine arising in combustion chambers.

The sensor of absolute pressure in the pipeline (MAR) (model since 1996 of the issue) - The sensor controls the depression depth variations in the inlet pipeline connected with changes of turns of a bent shaft and load of the engine and will transform the obtained information to an amplitude signal. Information arriving from the sensor is used by the module of management at failure diagnostics of the engine.

Measuring instrument of mass of air (MAF) - The MAF Sensor determines volume and weight parameters of the air stream coming to the inlet pipeline. As a sensitive element in the sensor filament is used. RSM uses information delivered by the MAR and IAT sensors at thin adjustments of parameters of injection.

The oxygen sensor (l-probe) - the Sensor develops a signal which amplitude depends on a ratio of amount of the oxygen (About ₂) which is contained in the fulfilled gases of the engine and external air. On the basis of information of RSM arriving from the sensor determines parameters of air-fuel mix, in due time carrying out its enrichment or impoverishment.

Sensor switch of pressure of working liquid of system of hydrostrengthening of a wheel (PSP) - On the basis of information of RSM arriving from the PSP sensor switch provides increase in turns of idling (due to operation of the IAC valve) for the purpose of compensation of the increasing loads of the engine connected with functioning of the steering hydraulic booster at commission of maneuvers.

Sensor of provision of a butterfly valve (TPS) - The sensor is located on the case of a throttle and connected to an axis of a butterfly valve. Determines the angle of opening of a butterfly valve (is operated by the driver from the accelerator pedal) by amplitude of the given TPS of a signal of RSM and as appropriate corrects supply of fuel to inlet ports of combustion chambers. The failure of the sensor, or weakening of its fastening leads to interruptions of injection and violations of stability of turns of idling.

Sensor of speed of the movement of the car (VSS) - As appears from its name, the sensor informs the processor on the current speed of the movement of the car.

Other, controlled RSM parameters - Besides given out by the listed above sensors on RSM also additional information on functioning of various knots and systems defining performance data of the engine arrives. To number other, systems and knots which control of functioning is exercised by RSM the following belongs:

a) Air conditioning system;
b) ABS;
c) Rechargeable battery (output tension);
d) EVAP system;
e) Ignition switch;
f) Sensor switch of permission of start;
g) Grounding chains;
h) Control system of functioning of transmission.

Actuation mechanisms

The relay of management of functioning of a clutch coupling To/in - RSM carries out shutdown of the K/V compressor during intensive acceleration.

Control lamp "Check the engine" - RSM makes inclusion of this control lamp at emergence of refusals of functioning of a control system of the engine.

The relay of management of functioning of fans of the cooling system - RSM exercises control of functioning of fans of the cooling system on the basis of the analysis of the signals arriving from the sensor of temperature of cooling liquid.

Vacuum electromagnetic valves of management of EGR - On models till 1999 the issue of RSM operates extent of opening of the vacuum EGR valve via the special intermediate electromagnetic valve.

EGR valve - On models of 1999 of the issue of RSM exercises control of a stream of recirculation of the fulfilled gases via the electronic EGR valve.

The valve of a purge of a coal adsorber - This electromagnetic valve, working at the command of RSM, carries out a purge of a coal adsorber of the EVAP system, removing the fuel evaporations which accumulated in it to the inlet highway of the engine.

The electromagnetic valve of management of turns of bystry idling - This valve is used on models since 1995 by the issue and serves for increase in turns of idling in cold weather. In fact this valve carries out a role of the air gate on carburetor models.

The forward support of a suspension bracket of the power unit - On the RSM some models controls also rigidity of a forward support of the engine depending on the speed of the movement of the car. Minimization of vibrations is carried out by the choice of one of two installations of a support.

Fuel injection injectors - RSM provides individual inclusion of each of injectors according to an established order of ignition. Besides, the module controls duration of opening of injectors determined by the width of the operating impulse measured in milliseconds and defining amount of the fuel injected into the cylinder. More detailed information on the principle of functioning of system of injection, replacement and service of injectors is provided in the Head of the Power supply system and release.

The relay of the fuel pump - the Relay is activated by the module of management when turning the ignition key in situation START/RUN. At inclusion of ignition of the relay carries out giving of food on a gasoline pump which provides rise in pressure in a path of a power supply system of the car. More detailed information on location and the principle of functioning of the relay is provided in Heads Onboard electric equipment and Power supply systems and release.

Valve of stabilization of turns of idling (IAC) - The IAC Valve carries out a dosage of amount of the air bypassed bypassing a butterfly valve when the last is closed or holds idling position. RSM operates opening of the valve and formation of the resulting air stream.

The heater of the oxygen sensor - Control of functioning of this device is exercised by RSM. The heater makes a bystry warming up of the l-probe up to the normal working temperature.

The power transistor - the Transistor carries out strengthening of a signal of the ignition developed by RSM and in the fullness of time makes instant grounding on the mass of primary contour of system of ignition that causes generation of VV of the signal given by the coil (Amy) directly on spark plugs in a secondary chain of system (for more details see the Head Elektrooborudovaniye of the engine).

Electromagnet of management of functioning of the valve of power - On models 1993 and 1994 of of the issue control of functioning of the valve of power is exercised by RSM by means of a special electromagnet.

Module of management of functioning of transmission (TSM) - TSM, being the module of management, separate of RSM, receives signals from various information sensors, such as VSS, the sensor switch of permission of start, the RPM meter of a shaft of the turbine, TPS, SMR, etc., and uses the accepted data when determining the moment of switching of transfer of AT demanded pressure in a path and the moment of blocking of the converter of rotation.

Reading of codes of malfunctions

At detection of the malfunction repeating in a row in spirit trips, RSM issues the command for inclusion of the control lamp which is built in in an instrument guard "Check the engine", called also by the indicator of refusals. The lamp will continue to burn until then, violation will not disappear, and will not be shown during three and more trips.

Reading of codes of malfunctions in the OBD-II system can be made in two ways. In the first case it is necessary to provide access to RSM for the purpose of switching of the selector to highlighting of codes by means of diagnostic lamps / a control lamp "Check the engine". RSM should remove from the basic arm (without disconnecting an electrical wiring) and to work according to the instructions given below.

Models 1993 and 1994 of of the issue.

a) Include ignition (without starting the engine). A control lamp "Check the engine" for dashboards has to remain included that confirms delivery of food on it from RSM and serviceability of the lamp.

Violation of an order of the procedure described below can lead to casual cleaning of memory of RSM!

b) By means of the screw-driver turn the selector on RSM wall against the stop clockwise. Diagnostic lamps have to begin to blink, - after three gleams turn the selector against the stop counterclockwise;
c) Attentively watch functioning of diagnostic lamps. The red light-emitting diode serves for highlighting of the first figure of a code of malfunction, the second figure of a code is highlighted by the green diode. For example, the code (TPS chain) 43 will look as follows: four gleams of the red diode, then three gleams green. Highlighting of a code 55 testifies to lack of the violations revealed by system (see below in the present Section the card of codes of malfunctions);
d) At repeated inclusion of ignition after switching off it in the course of reading of codes the system automatically cancels results of the previous search and the procedure of reading it is necessary to begin anew. Remark: Start of the engine automatically blocks access to system of self-diagnostics.

Models since 1995 of the issue.

a) Include ignition (without starting the engine). A control lamp "Check the engine" for dashboards has to remain included that confirms delivery of food on it from RSM and serviceability of the lamp.

Violation of an order of the procedure described below can lead to casual cleaning of memory of RSM!

b) By means of the screw-driver turn the selector on RSM wall against the stop clockwise. Diagnostic lamps have to begin to blink, - after three gleams turn the selector against the stop counterclockwise;
c) Attentively watch functioning of a control lamp "Check the engine". The lamp will highlight the first figure of a code a series long (approximately on 0.6 c) of gleams, then, after a 2-second pause, will start highlighting of the second figure of a code in the form of a series short (on 0.3 c) of gleams. For the purpose of definition of the highlighted code write down quantity of gleams of each series, so, the code 0403 (TPS chain) will look as follows: 4 long gleams, then, after a pause, three short. Highlighting of a code 0505 testifies to lack of the violations revealed by system (see below in the present Section the card of codes of malfunctions);
d) At repeated inclusion for zhiganiye after switching off it in the course of reading of codes the system automatically cancels results of the previous search and the procedure of reading it is necessary to begin anew. Remark: Start of the engine automatically blocks access to system of self-diagnostics.

The second method means use of the special scanner, and is applicable only on the models equipped with the OBD-II system (since 1995 the issue). with the help the scanner can be made deeper diagnostics of a condition of the engine and thin assessment of its working parameters. Besides, the scanner allows to make reading of the data frozen by the OBD system at the time of emergence of unstable refusal.

When using the scanner other form of record of codes is used, excellent from applied when reading by means of a control lamp "Check the engine". In this case the prefix of the P0 or P1 type is used (see the corresponding section of the table of the card of codes). In the absence of near at hand scanner diagnostics of unstable violations of a control system of the engine can be made only in the conditions of a workshop of car service.

Cleaning of memory of ECM/PCM

After the violations revealed in the course of diagnostics are eliminated, it is necessary to clear memory of RSM of the codes of malfunctions which are written down in it.

It is not necessary to make cleaning of memory by a detachment of a negative wire from the battery, - it will lead also to loss of basic parameters and violation of stability of turns of idling at first after start of the engine.

When using the scanner in the OBD-II systems it is necessary to transfer the device to the CLEARING CODES mode and to work according to instructions of manufacturers.

Models 1993 and 1994 of of the issue.

a) Consider the codes of malfunctions which are written down in memory of system;
b) Wait not less than two seconds, then turn the selector on RSM wall against the stop clockwise, - light-emitting diodes have to begin to blink;
c) After four gleams of diodes turn the selector against the stop counterclockwise;
d) Switch off ignition.

Models since 1995 of the issue.

a) Consider the codes of malfunctions which are written down in memory of system;
b) Wait not less than two seconds, then turn the selector on RSM wall against the stop clockwise;
c) Wait not less than two more seconds and turn the selector against the stop counterclockwise;
d) Switch off ignition.

Cleaning of memory has to be made always before the first start of the engine after replacement of components of a control system of the engine. If in memory of the module the code of malfunction any of information sensors was written down, then if after performance of replacement of the failed component to make start of the engine without memory cleaning, the old code will remain in force and the system will switch in the mode of basic installations, having eliminated the new sensor of working components.

Within the first 15 ÷ 20 seconds after the first start turns of the engine can remain unstable that is connected with restoration by the processor of performance data.

Identification of codes of malfunctions of system of an uparvleniye engine

The full map of possible codes of malfunctions is provided in Specifications, not all from which can take place for a concrete complete set of the car.