Diagnostics and checks (Focus 1)

European On-Board Diagnostics

European On-Board Diagnostics (EOBD) is a diagnostic system built into the powertrain control module (PCM). This system continuously monitors the emission control system components of the vehicle. The system includes a malfunction indicator lamp (MIL) that indicates that there is a problem that may affect emissions. The data stored in the module's DTC memory can be accessed using a universal scan tool (WDS).

EOBD is part of the European Standard Adaptation Directive, which has been in force since 2000. Only new petrol vehicles that comply with the latest EU directives (i.e. have an EOBD) will be eligible for registration in Europe. In Europe, diesel vehicles were not required to have an EOBD until 2003.

EOBD functions:

• Specifies when and how an indication of a malfunction of the emission control system must be given.
• Turns on the Malfunction Indicator Lamp (MIL) and activates the fault memory.
• Indicates the operating conditions under which the problem occurs (in freeze frame format).
• 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) plug in the instrument cluster area.
• It should be possible to show the nature of the problem through the use of a common system of codes.

The EOBD includes the following terms:

Cycle of movement

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

Drive

A trip begins when the engine is started and ends when all EOBD monitors complete a self-test. A trip may include a number of driving cycles.

Warm-up cycle

The warm-up cycle begins when the engine is started, starting with a coolant temperature of less than 35°C and ends when this temperature exceeds 70°C.

Data in frozen frame format

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

• Diagnostic trouble code.
• Car speed
• Engine coolant temperature.
• Engine crankshaft speed
• Engine load.
• Carburetion correction value (correction value for engine wear).
• Control status using oxygen sensors (open loop (without feedback)/closed loop (with feedback)).
• Mileage since the problem was first registered.

Dealer Check Cycle

After the problem has been corrected, especially after replacing the electronic engine control components, the DTC memory must be completely cleared. The DTC memory is part of the permanently stored memory (KAM) (non-volatile). After the DTC memory is cleared, a P1000 code is stored in the powertrain control module (PCM) memory. This readiness code indicates that because the KAM memory was cleared, not all monitoring systems have completed their tests. This code will not be cleared from the KAM memory until all monitors have completed their tests.

Monitors

The purpose of the monitors is to continuously check the operation of the 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 a way that is imperceptible to the vehicle driver. Each monitor operates under certain conditions of load, engine speed and temperature. Monitoring of all elements, combustion misfire monitoring and air/fuel ratio monitoring operate continuously. The remaining monitors are involved in work only under certain operating conditions.

All-Element Monitoring (CCM)

When the CCM detects a component operating out of range, it generates a diagnostic trouble code (DTC) that is stored in the KAM. If the same problem is confirmed on the next trip, the MIL will be illuminated. The CCM monitors many components, subsystems, and signals. The following is a list of those that affect emissions:

• Electronic Ignition System (EI)
• Crankshaft position (CKP) signal.
• Ignition coil
• Camshaft Position (CMP) signal.
• Air Conditioning (A/C) Clutch
• Control of the air supply in idle mode (IAC).
• Intake Manifold Runner Control (IMRC)
• Mass Air Flow (MAF)
• Intake Air Temperature (IAT)
• Engine Coolant Temperature (ECT)
• Cylinder Head Temperature (CHT)
• Throttle Position (TP)
• Constant Storage Memory (KAM)

Combustion Misfire Monitor

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

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

Type B: These can cause emissions to increase to levels above the EOBD threshold. If a misfire is detected during a specified number of engine revolutions during the second trip, the MIL will illuminate. If the misfire does not occur during the next three trips, the MIL will turn off.

Air/Fuel Ratio (AFR) Monitor

The HO2S, located before the catalytic converter (upstream sensor), measures the oxygen content in the exhaust gas and the change in that content. This allows the PCM to adjust the duration of the fuel injectors to maintain the correct AFR. This is known as the Current Fuel Trim (STFT). If the same change is detected a set number of times, a constant correction factor is used. This is known as the LTFT and is stored in the KAM. When the correction factors exceed the set values, a DTC will be stored in the KAM. If a problem is detected in either the STFT or LTFT and it still occurs on a second trip, the MIL will illuminate.

Heated Oxygen Sensor (HO2S) Monitor

This monitor monitors the performance of the front (before the catalytic converter) and rear (after the catalytic converter) HO2S sensors. It detects abnormal air/fuel ratio (AFR) conditions and sensor malfunctions.

Front HO2S Response Test: Checks whether the front HO2S sensor is able to switch quickly enough and whether the sensor output voltage is correct. Also checks the operation of the sensor heating element. This test is performed in closed loop control.

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 after a specified minimum temperature has been reached and turns off after a specified maximum temperature has been reached. The test determines whether the minimum and maximum voltages are within certain acceptable ranges. If they are not, the fuel system switches to open loop mode 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 efficiency of a converter decreases if it becomes 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 works by comparing the number of lean and rich switching cycles for the front and rear HO2S sensors. If the converter is working properly, this ratio should be approximately zero. When it approaches one, this indicates inefficient operation. At this point, no significant neutralization is occurring and the rear HO2S switches almost as much as the front HO2S. Therefore, the fewer the number of switching cycles of the lower HO2S sensor, the more efficient the neutralization process.

Diagnostic requirements

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, these make up a drive cycle. After any repairs that may have affected emissions, a dealer inspection cycle should be performed to ensure that the engine management system is operating correctly.

Malfunction Indicator Lamp (MIL)

The MIL is located on the instrument cluster and serves to alert the driver that there is a problem in the engine management system that is adversely affecting emissions. In the case of misfires that could damage the catalytic converter, it will illuminate immediately. For all other faults, it will remain illuminated after the second trip after the problem reoccurs. In normal operation, it should illuminate when the engine is started and go out immediately after the engine is started.

Diagnostic Trouble Codes

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

DTC is always a 5-digit alphanumeric code: for example, "P0100".

The first character of the code (letter) identifies the system that generated the code. In general, space has been reserved to identify four systems, although EOBD only requires the 'P' code.

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

All codes "x0xxx" are standardized codes. However, any manufacturer can use additional codes in addition to the standardized codes. They will be marked "x1xxx"

The third character of the code (number) identifies the subsystem that generated the code.

• 'Px1xx' for fuel dosing and air supply
• 'Px2xx' for fuel dosing and air supply
• 'Px3xx' for ignition system - combustion misfires
• 'Px4xx' for emission control accessories
• 'Px5xx' for vehicle speed, idle setting and other related input signals
• 'Px6xx' for trip computer and other related output signals
• 'Px7xx' for gearbox.
• 'Px8xx' for gearbox.
• 'Px9xx' - not yet defined
• 'Px0xx' - not yet defined

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

Inspection and verification

1. Check the validity of the customer's complaint by using the system.

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

Visual inspection table

Mechanical factors	Electrical factors
- Sensors – Executive devices	– Fuse(s) - Wiring harness – Electrical connector(s) – Powertrain Control Module (PCM) – Injector Control Module (IDM) - 115hp diesel vehicles.

3. If an obvious cause for the problem you have identified or the customer has described is found, correct it (if possible) before proceeding with further actions.

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