Diagnostics and checks

European on-board diagnostics

European on-board diagnostics (EOBD) is a diagnostic system built into the powertrain control module (PCM). This system continuously monitors elements of the vehicle's emission control system. The system includes a malfunction indicator lamp (MIL), which indicates that there is a problem that could affect emissions. Access to the data stored in the DTC memory of the module is possible through the use of a universal scan tool (WDS).

EOBD is part of the European Standard Adaptation Directive, which has been in effect since 2000. Only new vehicles with petrol engines meeting the latest European Union directives (those. having EOBD), will be eligible for registration in Europe. In Europe, diesel vehicles are not required to have EOBD until 2003.

EOBD Features:

• Establishes when and how an emission control failure should be indicated.
• Turns on the malfunction indicator lamp (MIL) and activates the fault memory.
• Indicates the operating conditions of the problem (in the format «frozen frame»).
• Standardized output of operating data such as engine speed, engine coolant temperature, etc.
• Standardized names/abbreviations for elements and systems.
• Standardized DTCs for all manufacturers.
• Standardized communication with diagnostic equipment.
• Standardized 16-pin data link connector (DLC) in the instrument panel area.
• Showing the nature of the problem should be possible through the use of a common coding system.

EOBD includes the following terms:

Movement cycle

The driving cycle starts when the engine is started (cold or warm) and ends when the engine is turned off.

Drive

The trip starts when the engine is started and ends when all EOBD monitors complete their self-test. A trip may include a number of traffic cycles.

Warm-up cycle

The warm-up cycle begins when the engine is started, starting at a coolant temperature below 35°C and ending when this temperature exceeds 70°C.

Data in format «frozen frame»

When a problem is detected, the following data is logged:

• Diagnostic Trouble Code.
• Vehicle speed
• Engine coolant temperature.
• Engine crankshaft speed
• Engine load.
• Mixture Correction Value (correction value for engine wear).
• Control status using oxygen sensors (open circuit (no feedback) / closed loop (with feedback)).
• Mileage since the problem was first reported.

Dealer Check Cycle

After the problem is corrected, especially after replacing the electronic engine controls, the DTC memory should be completely cleared. The DTC memory is part of the permanent storage memory (KAM) (non-volatile). After clearing the DTC memory to the powertrain control module memory (PCM) code P1000 is entered. This readiness code indicates what, because. KAM memory has been cleared, not all monitoring systems have completed their checks. This code will be removed from the KAM memory only after all monitors have finished their checks.

Monitors

The purpose of the monitors is to continuously check the operation of sensors and actuators responsible for reducing exhaust toxicity. It is established whether they all operate within the prescribed tolerances. All monitors perform their functions in such a way that it is imperceptible to the driver of the car. Each monitor operates under specific load, engine speed and temperature conditions. All element monitoring, combustion misfire monitoring and ratio monitoring «air / fuel» work continuously. The rest of the monitors are involved in the work only under certain operating conditions.

Monitoring of all elements (CCM)

When the CCM detects an element that is operating out of range, it will generate a DTC (DTC), which is written to KAM. If the same problem is confirmed on the next trip, the MIL will be turned on. The CCM controls many elements, subsystems and signals. The following is a list of what affects exhaust toxicity:

• Electronic ignition system (EI)
• crankshaft position signal (CKP).
• Ignition coil
• Camshaft position signal (CMP).
• Air Conditioning Coupling (A/C)
• Air supply control in idle mode (IAC).
• Intake manifold control (IMRC)
• Mass air flow (MAF)
• Air intake temperature (IAT)
• Engine coolant temperature (ECT)
• cylinder head temperature (CHT)
• Throttle position (TP)
• Persistent memory (KAM)

Combustion Misfire Monitor

The Misfire Combustion Monitor operates independently of other systems and can detect misfiring caused by the ignition system, fuel system, or mechanical engine components. As each cylinder enters the work, a characteristic acceleration of the crankshaft is created. Monitor detects deviations in acceleration pattern using crankshaft position sensor (CKP), and thus detects a misfire. It can also determine which cylinder has a misfire. Combustion misfires can be classified as follows:

Type A: They may cause damage to the catalytic converter due to increased internal temperature. If a certain number of misfires occur in a given number of engine revolutions, the MIL will illuminate to alert the driver that there is a problem.

Type B: They can increase emissions above the EOBD threshold. If a misfire is detected for a given number of engine revolutions on a second trip, the MIL will illuminate. If the misfire does not occur within the next three trips, the MIL will turn off.

Ratio Monitor «air / fuel» (AFR)

HO2S sensor installed in front of the catalytic converter (front sensor) measures the oxygen content in the exhaust gases and the change in this content. This gives the PCM the ability to adjust how long the fuel injectors are open to maintain the correct AFR ratio. This is known as «Current fuel trim» (STFT). If the same change is registered a predetermined number of times, a constant correction factor is used. This is known as «Predicted Fuel Trim» (LTFT), information about which is stored in KAM. When the correction factors exceed the set values, a DTC will be stored in the KAM memory. If a problem is detected in either the STFT or LTFT and it is still present on the second trip, the MIL will illuminate.

Heated oxygen sensor monitor (HO2S)

This monitor controls the operation of the front (before the catalytic converter) and rear (after catalytic converter) HO2S sensors. It determines the deviations in the ratio «air / fuel» (AFR) and sensor failures.

Front HO2S Response Test: Checks if the front HO2S is capable of switching fast enough and if the sensor output voltage is correct. The operation of the heating element of the sensor is also checked. This test is performed in closed loop control (with feedback).

Rear HO2S Test: This test only starts if the front sensor test has been successfully completed. To protect the rear HO2S, it only turns on when the set minimum temperature is reached and turns off when the set maximum temperature is reached. When checking, it is revealed whether the minimum and maximum voltages are in certain acceptable ranges. If not, the fuel system switches to open loop mode (no feedback) and is controlled using either a rich or lean mixture until the voltage returns to normal.

Catalytic Converter Efficiency Monitor

The efficiency of a catalytic converter is determined by its ability to store and then release oxygen to neutralize harmful gases. The effectiveness of the converter decreases when it is dirty, as it ages and at high gas consumption, because the exhaust gases do not remain in the converter long enough to complete the neutralization process.

The monitor operates on the principle of comparing the number of lean and rich shifts for the front and rear HO2S sensors. If the converter is working correctly, this ratio should be approximately zero. When it approaches one, it indicates inefficient work. At this point, no significant neutralization occurs and the rear HO2S switches almost exactly the same as the front HO2S. Therefore, the fewer the downstream HO2S switches, the more effective the neutralization process is.

Requirements for diagnostics

Vehicles equipped with EOBD can be diagnosed using the worldwide diagnostic system (WDS). To use the EOBD system, a number of criteria must be met. Together they make up a cycle of movement. After any repair that may have an effect on emissions, a dealer check cycle should be performed to verify that the engine management system is operating correctly.

Malfunction indicator lamp (MIL)

The MIL is located on the instrument panel and serves to alert the driver that there is a problem in the engine management system that is adversely affecting emissions. In the event of a misfire that could cause damage to the catalytic converter, it will light up immediately. For all other faults, it will stay lit after the second trip after the problem recurs. During normal operation, it should light up when the engine is started and go out immediately after the engine starts.

Diagnostic Trouble Codes

Diagnostic Trouble Codes (DTC), provided by PCM are standardized; this means that all manufacturers use identical codes.

• DTC is always a 5 digit alphanumeric code: for example, «P0100».

• First character of the code (letter) identifies the system that generated the code. In general, space has been reserved for the identification of four systems, although only the 'P' code is required for EOBD.

• 'B' - for body
• 'C' - for chassis
• 'P' - for the power unit
• 'U' - for data network systems

• All codes «x0xxx» are standardized codes. However, any manufacturer may use additional codes in addition to the standardized codes. They will be celebrated «x1xxx»

• Third character of the code (number) identifies the subsystem that generated the code.

• 'Px1xx' for fuel metering and air supply
• 'Px2xx' for fuel metering and air supply
• 'Px3xx' for ignition system - combustion misfire
• 'Px4xx' for emission control accessories
• 'Px5xx' for vehicle speed, idle setting and other relevant inputs
• 'Px6xx' for trip computer and other related outputs
• 'Px7xx' for gearbox.
• 'Px8xx' for gearbox.
• 'Px9xx' - not yet defined
• 'Px0xx' - not yet defined

• When a problem occurs, the emission reduction MIL is activated by the emission reduction code, which is part of the code required by law.

Inspection and verification

1. Check the legitimacy of the customer's complaint by activating the system.

2. Visually inspect for obvious signs of mechanical or electrical damage.

Visual Inspection Table

Mechanical factors	Electrical Factors
– Sensors – Executive devices	- Fuse (And) – wiring harness – Electrical connector (s) – Powertrain control module (PCM) – Injector control module (IDM) - cars with diesel engine 115 hp

3. If an obvious cause of the problem you identified or described by the client is found, eliminate it before proceeding to further actions (if possible).

4. If the cause is not visually obvious, check the symptom and refer to the WDS or equivalent scan tool for further diagnosis.