On-board diagnostics – memory. If normal condition is re-instated, the
5.4 On-board diagnostics – memory. If normal condition is re-instated, the
light extinguishes but the fault remains logged to
a second perspective
aid diagnostics. Circuits are monitored for open or short circuits as well as plausibility. When a
Authors note: The section on OBD repeats some of the information supplied previously but because this is
malfunction is detected, information about the such an important subject I decided that looking at it
malfunctioning component is stored. from two different view points would be useful. I am
An additional benefit allows the diagnostic most grateful to Dave Rogers (www .autoelex.co.uk)
technician to be able to access fault information for his excellent contribution to this chapter.
and monitor engine performance via data streamed
On-board diagnostics 75
California's Air Basins & Counties 1943: first smog alarm in LA
Northeast Plateau N 1950: 4,5 Mio. vehicles in california
Air Basin
County
1952: Dr. Arie Haagen-Smit analyses the reasons Sacramen to Valley WE
Mountain counties S 1960: 8 Mio. vehicles in California
for smog development
North Coast
Lake Tahoe 1961: introduction of crankcase ventilation (PCV)
Lake County
San Joaquin Valley 1966: Federal Clean Air Act
San Francisco Bay
1967: foundation of CARB, Chairman: Haagen-Smit Great Basin Valleys 1970: foundation of EPA
North Central Coast
1980: 17 Mio. vehicles in California Mojave Desert 1988: CARB decides OBD II for 1994 MY
South Central Coast
1990: number of smog days goes down, CARB decides LEV and ZEV – program
South Coast
Salton Sea 1996: Ozon-pollution 59% below 1965, number of smog days
1995: 26 Mio. vehicles in California
San Diego County
94% below 1975 Figure 5.18 History of CARB Emission legislation activity
directly from the ECU whilst the engine is running the current OBD2 standard. The OBD2 require- (on certain vehicles). This information can be
ment applies to all cars sold in the United States accessed via various scan tools available on the
from 1996. EOBD is the European equivalent market and is communicated in a standardised
of the American OBD2 standard, which applies format so one tool (more or less!) works with all
to petrol cars sold in Europe from 2001 (and vehicles. The data is transmitted in a digital form
diesel cars three years later). via this serial interface. Thus data values are trans-
OBD2 (also OBDII) was developed to address the mitted as data words and the protocol used for this shortcomings of OBD1 and make the system more data stream has to be known in order to evaluate user friendly for service and repair technicians. the information properly.
The benefits of having an OBD system are that it:
5.4.2 OBD2
Even though new vehicles sold today are cleaner encourages vehicle and engine manufacturers than they have ever been, the millions of cars on to have a responsible attitude to reducing the road and the ever increasing miles they travel harmful emissions from their engines via the each day make them our single greatest source of development of reliable and durable emission harmful emissions. While a new vehicle may start control systems;
out with very low emissions, infrequent maint- aids diagnosis and repair of complex elec- enance or failure of components can cause the tronic engine and vehicle control systems;
vehicle emission levels to increase at an undesir- reduces global emissions by identifying and able rate. OBD2 works to ensure that the vehicles highlighting immediately to the driver or user remain as clean as possible over their entire life emission control systems in need of repair;
(Figure 5.19). The main features of OBD2 are, provides ‘whole life’ emission control of the
therefore, as follows.
engine; ● on-board diagnostics, or OBD, was the name
● Malfunction of emission relevant components given to the early emission control and engine-
to be detected when emission threshold values management systems introduced in cars. There
are exceeded.
was no single standard – each manufacturer ● Storage of failures and boundary conditions in often using quite different systems (even
the vehicle’s fault memory. between individual car models). OBD systems
● Diagnostic light (MIL – Malfunction Indicator have been developed and enhanced, in line with
Light) to be activated in case of failures. United States government requirements, into
● Read out of failures with generic scan tool.
76 Advanced automotive fault diagnosis
Accelerator- Carbon canister
High pressure
pump
Injector
pedal module
Fuel rail
Ignition coil
Canister
Pressure control
purge valve
Phase sensor
valve
Oxygen Air-mass meter with
sensor temperature sensor
Fuel pressure
Temp. sensor
temperature sensor
Electronic NOx control unit
catalyst Diagnosis interface
Malfunction indicator lamp
Delivery module incl. low pressure pump
Oxygen Immobiliser
Bosch components specifically for DE sensor CAN
(LSF) Figure 5.19 OBD2 system showing the main components of a gasoline direct injection system (Source: Bosch Press)
Bosch components
The increased power of micro controllers (CPUs) The main features of an OBD2 compliant system in ECUs has meant that a number of important
(as compared to OBD1) are: developments could be added with the introduc-
● pre and post-catalyst oxygen sensors to moni- tion of OBD2. These include Catalyst efficiency
tor conversion efficiency; monitoring, misfire detection, canister purge and ● much more powerful ECU with 32bit processor; EGR flow rate monitoring. An additional benefit ● ECU Map data held on EEPROMS such that is the standardisation of diagnostic equipment they can be accessed and manipulated via an interfaces. external link. No need to remove ECU from For OBD1 each manufacturer applied speci- vehicle for software updates or tuning; fic protocols. With the introduction of OBD2 a ● more sophisticated EVAP system, can detect standardised interface was developed with a stand- minute losses of fuel vapour; ard connector for all vehicles, and a standardised ● EGR systems with feedback of position/flow theory for fault codes relating to the engine and
rate;
powertrain (more about this later). This meant that ● sequential fuel injection with MAP (Manifold
generic scan tools could be developed and used in Air Pressure) and MAF (Mass Air Flow) sens- the repair industry by diagnostic technicians to
ing for engine load.
aid troubleshooting of vehicle problems. Another feature of OBD2 is that the pre- scribed thresholds at which a fault is deemed to
5.4.3 EOBD
have occurred are in relation to regulated emis- sion limits. The basic monitor function is:
EOBD is an abbreviation of European on-board diagnostics. All petrol/gasoline cars sold in Europe
● monitoring of catalyst efficiency, engine misfire since 1 January 2001, and diesel cars manufactured and oxygen sensors function such that crossing
from 2003, must have on-board diagnostic sys-
a threshold of 1.5 times the emission limit will tems to monitor engine emissions. These systems record a fault;
were introduced in line with European directives to ● monitoring of the evaporation control sys-
monitor and reduce emissions from cars. All such tem such that a leak greater than the equiva-
cars must also have a standard EOBD diagnostic lent leak from a 0.04 inch hole will record
socket that provides access to this system. The
a fault. EOBD standard is similar to the US OBD2
On-board diagnostics 77
Table C Emission limits table for comparison
Legislation
OBD Malfunction Limit (grams/km)
⭓1.5 times the applicable federal standard EPA – Method
Multiplicative relative to limits
CARB 1 and 2 ⭓1.5 times the relevant CARB emission limits CARB 1 and 2 – Method
Multiplicative relative to limits
EOBD Positive lgn. 2000 0.40 3.20 0.60 – EOBD Diesel 2003
0.40 3.20 1.20 0.18 EOBD Positive lgn. 2005
0.20 1.40 0.30 – EOBD Diesel 2008 (for indication only)
0.30 2.40 0.90 0.14 EOBD – Method
Absolute limits
Table D Cars not exceeding 2.5 tonnes laden
Number Fuel
Implementation dates of seats
Directive
Limit values (gm/km)
Type approval In-use Euro III
01/01/00 01/01/01 up to 9
0.50 0.56 0.05 01/01/00 01/01/01 Note (i)
D 98/69/EC
0.65 0.72 0.07 01/01/01 01/01/02 Note (ii)
D 98/69/EC
0.78 0.86 0.10 01/01/01 01/01/02 Euro IV
D 98/69/EC
up to 9 P
01/01/05 01/01/06 up to 9
98/69/EC
01/01/05 01/01/06 Key: P – Petrol, D – Diesel, di – direct injection, CO – Carbon Monoxide, HC – Hydrocarbons, NOx – Oxides of Nitrogen, PM –
D 98/69/EC
Particulate mass Note (i) – Temporary concession for diesel cars over 2.0 tonnes laden weight which are off-road or more than six seats (unladen weight from 1206 to 1660 kg). Concession ceased on 31/12/02. Note (ii) – Temporary concession for diesel cars over 2.0 tonnes laden weight which are off-road or more than six seats (unladen weight over 1660 kg). Concession ceased on 31/12/02. Source: Vehicle Certification Agency manual, May 2005.
Table E Heavy motor car (more than 2.5 tonnes laden or more than six seats). Unladen weight between 1151 and 1600 kg
Number Fuel
Implementation dates of seats
Directive
Limit values (gm/km)
Type approval In-use Euro III
01/01/01 01/01/02 up to 9
98/69/EC
0.65 0.72 0.07 01/01/01 01/01/02 Euro IV
D 98/69/EC
up to 9 P
01/01/06 01/01/07 up to 9
98/69/EC
0.33 0.39 0.04 01/01/06 01/01/07 Key: P – Petrol, D – Diesel, di – direct injection, CO – Carbon Monoxide, HC – Hydrocarbons, NOx – Oxides of Nitrogen,
D 98/69/EC
PM – Particulate mass
standard. In Japan, the JOBD system is used. The ● January 2004 OBD for all new Diesel vehicles implementation plan for EOBD was as follows:
PC/LDV;
January 2005 OBD for all new Diesel vehicles January 2000 OBD for all new Petrol/Gasoline
HDV.
vehicle models; ● January 2001 OBD for all new Petrol/Gasoline
The EOBD system is designed, constructed and vehicles;
installed in a vehicle such as to enable it to iden- ● January 2003 OBD for all new Diesel vehicle
tify types of deterioration or malfunction over models PC/LDV;
the entire life of the vehicle. The system must be
78 Advanced automotive fault diagnosis
Table F Heavy motor car (more than 2.5 tonnes fully laden or more than six seats). Unladen weight over 600 kg
Number Fuel
Implementation Dates of seats
Directive
Limit values (gm/km)
Type Approval In-use Euro III
01/01/01 01/01/02 up to 9
98/69/EC
0.78 0.86 0.10 01/01/01 01/01/02 Euro IV
D 98/69/EC
up to 9 P
01/01/06 01/01/07 up to 9
98/69/EC
0.39 0.46 0.06 01/01/06 01/01/07 Key: P – Petrol, D – Diesel, di – direct injection, CO – Carbon Monoxide, HC – Hydrocarbons, NOx – Oxides of Nitrogen,
D 98/69/EC
PM – Particulate mass Note: The test procedure for Euro III and Euro IV is more severe than that for Euro I and Euro II. This results in some emission levels having an apparent increase when in fact they are more tightly controlled.
designed, constructed and installed in a vehicle
Compression ignition engines
to enable it to comply with the requirements dur- ● Where fitted, reduction in the efficiency of the ing conditions of normal use.
catalytic converter.
In addition, EOBD and OBD2 allow access ● Where fitted, the functionality and integrity of to manufacturer-specific features available on
the particulate trap.
some OBD2/EOBD compliant scan tools. This ● The fuel injection system electronic fuel quan- allows additional parameters or information to be
tity and timing actuator(s) is/are monitored for extracted from the vehicle systems. These are in
circuit continuity and total function failure. addition to the normal parameters and information
● Other emission control system components or available within the EOBD/OBD2 standard. These
systems, or emission-related powertrain com- enhanced functions are highly specific and vary
ponents or systems which are connected to a widely between manufacturers.
computer, the failure of which may result in tailpipe emission exceeding the specified limits
EOBD monitoring requirements on
given. Examples of such systems or compo-
the vehicle nents are those for monitoring and control of air
massflow, air volumetric flow (and tempera- The monitoring capabilities of the EOBD system
ture), boost pressure and inlet manifold pressure are defined for petrol/gasoline (spark ignition)
(and relevant sensors to enable these functions and diesel (compression ignition) engines. The
to be carried out).
following is an outline. ● Any other emission-related powertrain com- ponent connected to a computer must be moni-
Spark ignition engines
tored for circuit continuity. ● Detection of the reduction in the efficiency of