The OBD-II standard (On-Board Diagnostic) was implemented initially by the CARB (Californian Air Resources Board) to control the polluting emissions from vehicles. The arrival of electronic computers to manage the engine and associated computers enabled vehicles to reduce their pollutants. The OBD states that a vehicle should permanently monitor the smooth operation of the engine throughout its life
The OBD stands for On/Off-Board Diagnostic, Basically, this OBD-II term is used in the automotive vehicles for the diagnostic of the vehicle. Now you would have thought about diagnostic which means to find the cause or fault of a problem. If you are a man and going to the hospital if you have any problem then you can think and explain it to the doctor and he will give you the solution. But if any problem is occurring in your vehicle, then how the vehicle will explain it to the service engineer when any fault is happening as he is a machine whose not having the thinking capability. If you are purchasing a vehicle and going to the service center where if you don’t know the proper fault, then they will check everything one by one and they might be again made some problem and more time, more cost, they will put some more parts which might cost you more for which you can’t say anything. So to prevent this nowadays most of the OEM started using the diagnostic system in the vehicle. Basically the Diagnostic is of having two types as:
- On-Board Diagnostic.
- Off-Board Diagnostic.
(1) Off-Board Diagnostic: If the fault is happening and to detect the fault, the diagnostic engineer using some external tool to do the diagnostic on the vehicle and fix the problem, then this is called Off-Board diagnostic.
(2) On-Board Diagnostic: If any fault will occur in the vehicle and the OEM is already has been implemented some codes to check the fault periodically in every ECU to detect the fault and immediately inform the owner about the fault, then this is called an On-Board Diagnostic.
Since the On-Board diagnostic or OBD-II is the concept to which all the OEM’s are following which really helping them to do the self-diagnostic in-vehicle system and also save the money mostly they are using the term OBD means On-Board diagnostic. So that now I am going to explain this On-Board diagnostic so from next time onward you have to understand OBD means On-Board Diagnostic.
The OBD-II is a term that is used for self-diagnostic and reporting capability. First, automotive OEM has started this concept to give safety to the engine A basic OBD system consists of an ECU (Electronic Control Unit), which uses input from various sensors (e.g., oxygen sensors) to control the actuators (e.g., fuel injectors) to get the desired performance. The “Check Engine” light, also known as the MIL (Malfunction Indicator Light), provides an early warning of malfunctions to the vehicle owner. A modern vehicle can support hundreds of parameters, which can be accessed via the DLC (Diagnostic Link Connector) using a device called a scan tool.
There are two types of OBD are available which are using in vehicles for fault diagnostic. Such as OBD-I & OBD-II.OBD-I: The OBD-I refers to the first generation OBD systems that were developed throughout the 1980s. These early systems use proprietary connectors, hardware interfaces, and protocols. A mechanic who wanted to access the diagnostic information typically had to buy a tool for every different vehicle make. OBD-I scan tools that support multiple protocols are supplied with an array of different adapter cables. This standard was very difficult to manage with different automotive makers for a mechanic. Then the OBD-II came to the automotive industry which solves all the problems
OBD-II: Unlike earlier, OEM-specific OBD-I systems, The OBD-II systems use the same communication protocols, code designations, and connectors from one manufacturer to another. This allows a single OBD-II scanner to provide access to the data that these systems are capable of providing across all makes and models of vehicles produced since 1996, which was the first model year that OBD-II was required across the board. In the early 1990s, the Society of Automotive Engineers (SAE) and International Standardization Organization (ISO) issued a set of standards that described the interchange of digital information between ECUs and a diagnostic scan tool. All OBD-II compliant vehicles were required to use a standard diagnostic connector (SAE J1962), and communicate via one of the standard OBD-II communication protocols.
OBD-II has first introduced in model year (MY) 1994 vehicles and became a requirement for all cars and light trucks starting with MY1996. Virtually every new car sold in the U.S. over the past 20 years follows the OBD-II standard. OBD-II cars have a port — usually located under the dashboard on the driver’s side — that devices can plug into and connect to a car’s computer. Companies have plenty of ideas about what you can plug into that port.
Types Of OBD-II Scanners: There are basically two types of OBD-II scanners that you will come across in the wild.
(1) OBD-II Code Reader.
(2) OBD-II Scan Tool.
(1) OBD-II Code Reader: The OBD-II code (DTC) reader is one of the simplest vehicle diagnostic tool used to read the fault codes from the vehicle. These devices are designed to interface with a car’s computer and report trouble codes in a very no-frills sort of way. Cars and trucks that were built prior to 1996 require specific, proprietary code readers, and newer vehicles use universal code readers. This type of car code reader is typically inexpensive, and some parts stores and shops will even read your codes for free. The OBD-II code readers are typically inexpensive.
Features of OBD-II Code Reader:
(a) Read and Clear of fault codes(DTC).
(b) Check of view of basic Parameter ID’s.
(c) Check and possibly reset readiness monitors.
(2) OBD-II Scan Tool: An OBD scan tool is a vehicle diagnostic scan tool which is the advanced version of the Code reader tool. The OBD scan tool exhibits a wide range of features. The scan tools typically include a code reader, which
What Can a Scan Tool Do?
The scan tools are designed to interface with a car’s “onboard diagnostic” system in order to facilitate the diagnostic process. In that way, they are a lot like car code readers. They can be plugged into an OBD-I or OBD-II socket, read and clear codes, and view data readouts from various sensors. However, scan tools go beyond that basic functionality.
Featurs Of OBD Scan Tool:
- It can Store and playback live data.
- It can Display Graph data.
- It can Read both generic and manufacturer-specific trouble codes.
- It can Display pending codes.
- It can Provide trouble code definitions.
- It can Provide troubleshooting procedures or tips.
OBD-II Connector: The OBD-II connector is available in every vehicle nowadays through which the diagnostic engineer will connect the OBD/diagnostic tool with the vehicle to find the faults. Nowadays the OEM’s are also providing wireless communication like Bluetooth/Wi-fi through which users can connect the Diagnostic tool or the android software provided by the Manufacturer to scan the faults.
But there is a standard that all the OEM are following and providing the OBD-II connector port in the vehicle. The SAE-J1962 specification provides for two standardized hardware interfaces, called type A and type B. Both are female, 16-pin (2×8), D-shaped connectors, and both have a groove between the two rows of pins, but type B’s groove is interrupted in the middle. This prevents the insertion of a type A male plug into a type B female socket while allowing a type B male plug to be inserted into a type A female socket.
(a) Type-A OBD connector: The type-A OBD connector is used for vehicles that use 12V supply voltage.
(b) Type-B OBD connector: The type-B is used for 24V vehicles and it is required to mark the front of the D-shaped area in blue color.
The SAE J1962 standard OBD-II Connector details
1. GM: J2411 GMLAN/SWC/Single-Wire CAN
2. VW/Audi/BMW: Switched +12V to tell a
scan tool whether the ignition is on.
3. Ford, FIAT: Infotainment CAN High
4. DoIP Option #2 Ethernet RX+
1. BMW: TD (Tachometer Display) signal aka engine RPM signal.
2. GM: 8192 bit/s ALDL where fitted.
3. DoIP Option #2 Ethernet RX-
|2||Bus Positive Line of SAE J-1850 PWM and VPW||10||Bus Negative Line of SAE J1850 PWM only (not SAE J1850 VPW)|
1. GM: Object Detection CAN bus (+)
2. Ford: DCL(+) Argentina, Brazil (pre OBD-II) 1997–2000, USA, Europe, etc.
3. Ford: Medium Speed CAN-High
4. Chrysler: CCD Bus(+)
5. BMW: Ethernet RX+
6. DoIP Option #1 Ethernet RX+
1. GM: Object Detection CAN bus (-)
2. Ford: DCL(-) Argentina, Brazil (pre OBD-II) 1997–2000, USA, Europe, etc.
3. Ford: Medium Speed CAN-Low
4. Chrysler: CCD Bus(-)
5. BMW: Ethernet RX-
6. DoIP Option #1 Ethernet RX-
1. GM: Chassis high-speed CAN bus (+)
2. GM: Diagnostic codes to DIC (1994–2004 Corvette)
3. BMW: Ethernet TX+
4. DoIP Ethernet TX+
1. GM: Chassis high-speed CAN bus (-)
2. Ford: FEPS – Programming PCM voltage
3. BMW: Ethernet TX-
4. DoIP Ethernet TX-
CAN-High (ISO 15765-4 and SAE J2284)
CAN-Low (ISO 15765-4 and SAE J2284)
K-Line of ISO 9141-2 and ISO 14230-4
L-Line of ISO 9141-2 and ISO 14230-4
1. BMW: Second K-Line for non OBD-II (Body/Chassis/Infotainment) systems.
2. Ford, FIAT: Infotainment CAN-Low.
3. BMW: Ethernet Enable via 510 Ohm, 0,6 Watt resistance to battery voltage (pin 16)
4. DoIP: Ethernet Activate
5. Subaru: Ignition+.
1. Type “A” 12V/4A
2. Type “B” 24V/2A
Unlike the OBD-I connector, which was sometimes found under the hood of the vehicle, the OBD-II connector is required to be within 2 feet (0.61 m) of the steering wheel (unless an exemption is applied for by the manufacturer, in which case it is still somewhere within reach of the driver).
The data coming from OBD-II is of two forms: Diagnostics Trouble Codes and Real-time monitoring. Real-time data can be acquired and stored for further processing and analysis.
How to understand the OBD-II Code:
When the scanner finishes booting up, look for a menu. Select “Codes” or “Trouble Codes” to open the main Codes menu. Depending on your scanner and year of the vehicle you may be presented with a few systems such as Engine/Powertrain, Transmission, Airbag, Brakes, etc. When you pick one, you will see two or more types of codes. The most common are Active codes and Pending codes.
- Active codes are live codes or malfunctions that are keeping your Check Engine Light on. Just because your Check Engine Light is off doesn’t mean the code or malfunction disappeared, it just means that the code setting conditions haven’t occurred for two or more operations of the vehicle.
- Pending codes mean that the OBD-II monitoring system has failed the operation of an emission control system at least once and if it fails again the Check Engine Light will be turned on and the malfunction becomes an Active code.
what system the code is referring to. There are several letters that you may see, though you may have to move to different menus to see them:
- P – Powertrain. This covers the engine, transmission, fuel system, ignition, emissions, and more. This is the largest set of codes.
- B – Body. This covers airbags, seat belts, power seating, and more.
- C – Chassis. These codes cover ABS, brake fluid, axles, and more.
- U – Undefined. These codes cover other aspects of the car.
How to detect the type of DTC from it’s character Name:?
P0xxx, P2xxx, and P3xxx are all generic codes that apply to all makes and models. P1xxx codes are manufacturer specific, such as Honda, Ford, Toyota, etc. The second number tells you what subsystem the code refers to. For example, P07xx codes refer to transmission.
Read an example code: In OBD-II standard, P0301 indicates a misfire condition on cylinder #1. The P indicates it’s a powertrain code, the 0 indicates that it is a generic or universal code. The 3 means the area or subsystem is an Ignition System code.
- The 01 indicates it’s a cylinder specific problem, in that there is a misfire condition in the number 1 cylinder. It could mean that the spark plug, plug wire, or dedicated ignition coil are worn out or that there is a vacuum leak near the cylinder.
- Code does not tell you what component is defective; it only points to or indicates that a component, its circuit, or its wiring/vacuum control are malfunctioning. The code may be the symptom of a malfunction caused by a completely different system.
How Diagnose your vehicle:
The proper diagnosis of OBD-II codes takes years of training and practice. For example, a weak battery or worn out alternator can set five or more codes in systems that are perfectly normal. Before attempting repairs, understand that the codes alone will not tell you what parts need to be replaced or what repairs need to be made.
- If you are unsure of what you are doing, take your car to an ASE Certified Master Technician with the L1 Advanced Engine Performance Diagnostic certification, or you could end up wasting a lot of time and money.
What OBD-II can do?
It can read the faults from the vehicle for diagnostic and it also can monitor the vehicle.
EngineeParameters: The engineparameters likeRPM, VSS, MAF, MAP, Coolant Temperature, Power, Torque, & engineload, etc. can be gathered.
- Developing Drive Cycles
: Gearinformation, engineRPM, throttle position, torque, speed, & power can be recorded which later can be used to develop the drive cycles for testing.
- Determining Fuel Economy: The various parameters
likeMAF, MAP, IAT, & VSS data can be used to determine the fuel economy of the vehicle.
- Understanding Drive Patterns: The OBD-II data can be used to monitor the drive patterns which can help in analyzing the driving
habitsof a person. The insurance companiesare trying to link the insurance of a vehicle with the driving pattern of the person.
- Traffic Conditio0ns: The traffic conditions can be categorized based on speed & RPM. The GPS location can be logged to find the traffic zones. This can be done by connecting a small OBD-II device to the car OBD port.
How to read DTC from Vehicle using different Diagnostic Service?
The OBD-II PIDs (On-board diagnostics parameter IDs) are codes used to request data from a vehicle, used as a diagnostic tool. SAE standard J1979 defines many OBD-II PIDs. All on-road vehicles and trucks sold in North America are required to support a subset of these codes, primarily for state-mandated emissions inspections. Manufacturers also define additional PIDs specific to their vehicles. Though not mandated, many motorcycles also support OBD-II PIDs.
OBD-II Modes Of Services:
There are 10 diagnostic services described in the latest OBD-II standard SAE J1979. Before 2002, J1979 referred to these services as “modes”. They are as follows:
|0x01||Show current data|
|0x02||Show freeze frame data|
|0x03||Show stored Diagnostic Trouble Codes|
|0x04||Clear Diagnostic Trouble Codes and stored values|
|0x05||Test results, oxygen sensor monitoring (non CAN only)|
|0x06||Test results, other component/system monitoring (Test results, oxygen sensor monitoring for CAN only)|
|0x07||Show pending Diagnostic Trouble Codes (detected during current or last driving cycle)|
|0x08||Control operation of on-board component/system|
|0x09||Request vehicle information|
|0x0A||Permanent Diagnostic Trouble Codes (DTCs) (Cleared DTCs)|
The vehicle manufacturers are not required to support all services. Each manufacturer may define additional services above #9 (e.g.: service 22 as defined by SAE J2190 for Ford/GM, service 21 for Toyota) for other information e.g. the voltage of the traction battery in a hybrid electric vehicle (HEV).
Mode-1 Pids: Mode 1 is used to know the current value of the corresponding PID. Mode 2 is used to know the state of the PIDs when a fault is detected.
|00||00||List of PIDs supported (range 01 to 32)|
|01||01||Status since the last clearing of fault codes|
|02||02||Fault code that caused the recording of “freeze frame” data|
|03||03||Fuel system status|
|04||04||Engine load calculated in %|
|05||05||Temperature of the engine coolant in °C|
|06||06||Short-term fuel % trim bank 1|
|07||07||Long-term fuel % trim bank 1|
|08||08||Short-term fuel % trim bank 2|
|09||09||Long-term fuel % trim bank 2|
|0A||10||Fuel pressure in kPa|
|0B||11||Intake manifold absolute pressure in kPa|
|0C||12||Engine speed in rpm|
|0D||13||Vehicle speed in kph|
|0E||14||Timing advance on cylinder 1 in degrees|
|0F||15||Intake air temperature in °C|
|10||16||Air flow measured by the flowmeter in g/s|
|11||17||Throttle position in %|
|12||18||Status of the secondary intake circuit|
|13||19||O2 sensor positions bank/sensor|
|14||20||Oxygen sensor volts bank 1 sensor 1/td>|
|15||21||Oxygen sensor volts bank 1 sensor 2|
|16||22||Oxygen sensor volts bank 1 sensor 3|
|17||23||Oxygen sensor volts bank 1 sensor 4|
|18||24||Oxygen sensor volts bank 2 sensor 1|
|19||25||Oxygen sensor volts bank 2 sensor 2|
|1A||26||Oxygen sensor volts bank 2 sensor 3|
|1B||27||Oxygen sensor volts bank 2 sensor 4|
|1C||28||OBD computer specification|
|1D||29||O2 sensor positions bank/sensor|
|1E||30||Auxiliary input status|
|1F||31||Run time since engine start|
|20||32||List of PIDs supported (range 33 to 64)|
|21||33||Distance travelled with MIL on in kms|
|22||34||Relative fuel rail pressure in kPa|
|23||35||Fuel rail pressure in kPa|
|24||36||O2 sensor (extended range) bank 1, sensor 1 (lambda and volts)|
|25||37||O2 sensor (extended range) bank 1, sensor 2 (lambda and volts)|
|26||38||O2 sensor (extended range) bank 1, sensor 3 (lambda and volts)|
|27||39||O2 sensor (extended range) bank 1, sensor 4 (lambda and volts)|
|28||40||O2 sensor (extended range) bank 2, sensor 1 (lambda and volts)|
|29||41||O2 sensor (extended range) bank 2, sensor 2 (lambda and volts)|
|2A||42||O2 sensor (extended range) bank 2, sensor 3 (lambda and volts)|
|2B||43||O2 sensor (extended range) bank 2, sensor 4 (lambda and volts)|
|2C||44||EGR in %|
|2D||45||EGR error in %|
|2E||46||Evaporation purge in %|
|2F||47||Fuel level in %|
|30||48||Number of warning(s) since faults (DTC) were cleared|
|31||49||Distance since faults (DTC) were cleared.|
|32||50||Evaporation system vapour pressure in Pa|
|33||51||Barometic pressure in kPa|
|34||52||O2 sensor (extended range) bank 1, sensor 1 (lambda and volts)|
|35||53||O2 sensor (extended range) bank 1, sensor 2 (lambda and volts)|
|36||54||O2 sensor (extended range) bank 1, sensor 3 (lambda and volts)|
|37||55||O2 sensor (extended range) bank 1, sensor 4 (lambda and volts)|
|38||56||O2 sensor (extended range) bank 2, sensor 1 (lambda and volts)|
|39||57||O2 sensor (extended range) bank 2, sensor 2 (lambda and volts)|
|3A||58||O2 sensor (extended range) bank 2, sensor 3 (lambda and volts)|
|3B||59||O2 sensor (extended range) bank 2, sensor 4 (lambda and volts)|
|3C||60||Catalyst temperature in °C bank 1, sensor 1|
|3D||61||Catalyst temperature in °C bank 2, sensor 1|
|3E||62||Catalyst temperature in °C bank 1, sensor 2|
|3F||63||Catalyst temperature in °C bank 2, sensor 1|
|40||64||List of PIDs supported (range 65 to 96)|
|41||65||Monitor status this drive cycle|
|42||66||Control module voltage in V|
|43||67||Absolute engine load|
|44||68||Equivalent fuel/air mixture request|
|45||69||Relative throttle position in %|
|46||70||Ambient air temperature in °C|
|47||71||Absolute throttle position B in %|
|48||72||Absolute throttle position C in %|
|49||73||Accelerator pedal position D in %|
|4A||74||Accelerator pedal position E in %|
|4B||75||Accelerator pedal position F in %|
|4C||76||Commanded throttle actuator in %|
|4D||77||Engine run time since MIL on in min|
|4E||78||Engine run time since faults cleared in min|
|4F||79||Exteral test equipment no. 1 configuration information|
|50||80||Exteral test equipment no. 2 configuration information|
|51||81||Fuel type used by the vehicle|
|52||82||Ethanol fuel %|
|53||83||Absolute evaporation system vapour pressure in kPa|
|54||84||Evaporation system vapour pressure in Pa|
|55||85||Short-term O2 sensor trim bank 1 and 3|
|56||86||Long-term O2 sensor trim bank 1 and 3|
|57||87||Short-term O2 sensor trim bank 2 and 4|
|58||88||Long-term O2 sensor trim bank 2 and 4|
|59||89||Absolute fuel rail pressure in kPa|
|5A||90||Relative accelerator pedal position in %|
|5B||91||Battery unit remaining life (hybrid) in %|
|5C||92||Engine oil temperature in °C|
|5D||93||Fuel injection timing in °|
|5E||94||Fuel consumption in litre/hr|
|5F||95||Fuel consumption in litre/hr|
|60||96||List of PIDs supported (range 97 to 128)|
|61||97||Driver demand: torque percentage (%)|
|62||98||Final engine torque percentage (%)|
|63||99||Engine torque reference in Nm|
|64||100||Engine torque data in %|
|65||101||Auxiliary inputs / outputs|
|67||103||Engine water temperature in °C|
|68||104||Air temperature sensor in °C|
|69||105||Commanded EGR and EGR error|
|6A||106||Commanded Diesel intake air flow control and relative intake air flow position|
|6B||107||Recirculation gas temperature in °C|
|6C||108||Commanded throttle actuator control and relative throttle position|
|6D||109||Fuel pressure control system|
|6E||110||Injection pressure control system|
|6F||111||Turbocharger compressor inlet pressure in kPa|
|70||112||Boost pressure control in kPa|
|71||113||Variable Geometry turbo (VGT) control|
|73||115||Exhaust pressure in kPa|
|75||117||Turbocharger A temperature in °C|
|76||118||Turbocharger B temperature in °C|
|77||119||Charge air cooler temperature in °C|
|78||120||Exhaust Gas temperature (EGT) Bank 1|
|79||121||Exhaust Gas temperature (EGT) Bank 2|
|7A||122||Diesel particulate filter (DPF) bank 1|
|7B||123||Diesel particulate filter (DPF) bank 2|
|7C||124||Diesel Particulate filter (DPF) temperature|
|7D||125||NOx NTE control area status|
|7E||126||PM NTE control area status|
|7F||127||Engine run time|
|80||128||List of PIDs supported (range 129 to 160)|
|00||00||List of PIDs supported (range 01 to 32)|
|01||01||Rich to lean sensor threshold voltage|
|02||02||Lean to rich sensor threshold voltage|
|03||03||Low voltage used to calculated passage time|
|04||04||High voltage used to calculated passage time|
|05||05||Rich to lean calculated passage time|
|06||06||Lean to rich calculated passage time|
|07||07||Minimum sensor voltage during test cycle|
|08||08||Maximum sensor voltage during test cycle|
|09||09||Time between sensor transitions|
|0B||11||Reserved for future use|
OBD-II: The OBD-II is still a concept, is an advancement over OBD-II which will be equipped with telemetry. Using a radio transponder, OBD-III equipped vehicles will be able to send emissions problems directly to the regulating authority. It will report the Vehicle Identification Number (VIN) and the DTC. This can be done via cellular or satellite link as soon as the MIL turns on. This will help in cost savings as only vehicles with emission problems need to be tested.