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OBD stands for on-board diagnostics and defines the modern fuel managed vehicle's electronic interface system.
This introduction should be helpful in giving full details on the features of OBD and the benefits of diagnosing your own vehicle and fault clearing when faults are found.
On which vehicles does OBD work?
The OBD interface is available on all OBD-II / EOBD compliant vehicles. 2001 and
newer petrol cars sold in Europe are EOBD compliant. Diesel (compression
ignition) vehicles were not required to support OBD until 2004. Some
pre-2001 petrol vehicles and pre-2004 diesel vehicles have a 16-pin connectors
but they may not be OBD-II or EOBD compliant.
16 Pin OBD Connector
Locating your OBD connector can be a difficult task as vehicle manufacturers tend to hide away the socket. But it is worth knowing that the OBD connector will always be found inside the vehicle and within easy reach from the driver's set position. Check in the driver's foot well, under the steering wheel, behind panels in the dashboard fascia and the central area between the driver's seat and the passenger seat. Some connectors have been located behind ashtrays, under the passenger seat and even over by the passengers door.
Once you find the OBD connector, check which pins which are present. The view above is shown looking into the connector, with the locating "bump" at the bottom.
The connector must have pins 4, 5 for ground connections and pin 16 for 12 volt power supply from the vehicle battery.
The following connections are dependent on the protocol in use by the vehicle:
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Pin 2 and pin 10 for SAE J1850 (PWM or VPWM) protocols.
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Pin 7 for ISO 9141-2 and ISO 14230 (KWP2000) communications. Pin 7 is also known as the K-Line.
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Pin 15 is also known as the L-Line. may or may not be present for these protocols.
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Pin 6 and pin 14 are present for CAN bus (ISO 15765-4) protocols.
Generally speaking the following vehicles have these protocols:
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VPWM: General Motors, Chrysler
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PWM: Ford models to 2003 with EEC-V engine management system. Including Ford Cougar (all UK models), Ford Puma (1.6 and 1.7), Ford Fiesta Zetec models to 2003, Ford Mondeo Zetec models to 2003, Ford Focus to 2003. Newer Jaguar S-Type and Jaguar X-Type. Pre 2004 Mazdas
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ISO / KWP2000: Most European and Asian manufacturers. Alfa Romeo, Audi, BMW, Citroen, Fiat, Honda, Hyundai, Jaguar (X300, XK), Jeep since 2004, Kia, Land Rover, Mazda, Mercedes, Mitsubishi, Nissan, Peugeot, Renault, Saab, Skoda, Subaru, Toyota, Vauxhall, Volkswagen (VW) since 2001, Volvo to 2004 :: More information on KWP 2000 (ISO 14230)...
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CAN: Ford, Mazda, Volvo since 2004. Some vehicles have a CAN bus system along side the ISO/KWP2000 system for diagnostics as well as inter-module communications. ::More information on CAN bus technology...
OBD-II Standard Mode 1 Services
The OBD standard specifies modes by which an OBD-II compliant ECU will respond. Mode 1 is used mostly for reading sensor data from the ECU. The following table shows the commands standardised in OBD-II for Mode 1 use.
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Mode 1 Service Commands Table |
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Monitor status since DTCs cleared |
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DTC that caused required freeze frame data storage |
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Fuel system 1 and 2 status |
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Calculated LOAD Value |
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Engine Coolant Temperature |
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Short Term Fuel Trim - Bank 1 |
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Long Term Fuel Trim - Bank 1 |
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Short Term Fuel Trim - Bank 2 |
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Long Term Fuel Trim - Bank 2 |
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Fuel Rail Pressure (gauge) |
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Intake Manifold Absolute Pressure |
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Engine RPM |
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Vehicle Speed Sensor |
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Ignition Timing Advance for #1 Cylinder |
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Intake Air Temperature |
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Air Flow Rate from Mass Air Flow Sensor |
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Absolute Throttle Position |
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Commanded Secondary Air Status |
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Location of Oxygen Sensors |
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Bank 1 - Sensor 1/Bank 1 - Sensor 1 Oxygen Sensor Output Voltage / Short Term Fuel Trim |
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Bank 1 - Sensor 2/Bank 1 - Sensor 2 Oxygen Sensor Output Voltage / Short Term Fuel Trim |
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Bank 1 - Sensor 3/Bank 2 - Sensor 1 Oxygen Sensor Output Voltage / Short Term Fuel Trim |
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Bank 1 - Sensor 4/Bank 2 - Sensor 2 Oxygen Sensor Output Voltage / Short Term Fuel Trim |
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Bank 2 - Sensor 1/Bank 3 - Sensor 1 Oxygen Sensor Output Voltage / Short Term Fuel Trim |
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Bank 2 - Sensor 2/Bank 3 - Sensor 2 Oxygen Sensor Output Voltage / Short Term Fuel Trim |
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Bank 2 - Sensor 3/Bank 4 - Sensor 1 Oxygen Sensor Output Voltage / Short Term Fuel Trim |
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Bank 2 - Sensor 4/Bank 4 - Sensor 2 Oxygen Sensor Output Voltage / Short Term Fuel Trim |
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OBD requirements to which vehicle is designed |
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Location of oxygen sensors |
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Auxiliary Input Status |
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Time Since Engine Start |
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Distance Travelled While MIL is Activated |
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Fuel Rail Pressure relative to manifold vacuum |
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Fuel Rail Pressure |
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Bank 1 - Sensor 1/Bank 1 - Sensor 1 (wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Voltage |
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Bank 1 - Sensor 2/Bank 1 - Sensor 2 (wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Voltage |
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Bank 1 - Sensor 3 /Bank 2 - Sensor 1(wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Voltage |
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Bank 1 - Sensor 4 /Bank 2 - Sensor 2(wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Voltage |
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Bank 2 - Sensor 1 /Bank 3 - Sensor 1(wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Voltage |
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Bank 2 - Sensor 2 /Bank 3 - Sensor 2(wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Voltage |
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Bank 2 - Sensor 3 /Bank 4 - Sensor 1(wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Voltage |
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Bank 2 - Sensor 4 /Bank 4 - Sensor 2(wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Voltage |
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Commanded EGR |
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EGR Error = (EGR actual - EGR commanded) / EGR commanded * 100% |
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Commanded Evaporative Purge |
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Fuel Level Input |
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Number of warm-ups since diagnostic trouble codes cleared |
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Distance since diagnostic trouble codes cleared |
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Evap System Vapour Pressure |
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Barometric Pressure |
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Bank 1 - Sensor 1/Bank 1 - Sensor 1 (wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Current |
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Bank 1 - Sensor 2/Bank 1 - Sensor 2 (wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Current |
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Bank 1 - Sensor 3/Bank 2 - Sensor 1 (wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Current |
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Bank 1 - Sensor 4/Bank 2 - Sensor 2 (wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Current |
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Bank 2 - Sensor 1/Bank 3 - Sensor 1 (wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Current |
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Bank 2 - Sensor 2/Bank 3 - Sensor 2 (wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Current |
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Bank 2 - Sensor 3/Bank 4 - Sensor 1 (wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Current |
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Bank 2 - Sensor 4/Bank 4 - Sensor 2 (wide range O2S) Oxygen Sensors Equivalence Ratio (lambda) / Current |
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Catalyst Temperature Bank 1 / Sensor 1 |
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Catalyst Temperature Bank 2 / Sensor 1 |
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Catalyst Temperature Bank 1 / Sensor 2 |
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Catalyst Temperature Bank 2 / Sensor 2 |
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Monitor status this driving cycle |
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Control module voltage |
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Absolute Load Value |
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Commanded Equivalence Ratio |
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Relative Throttle Position |
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Ambient air temperature |
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Absolute Throttle Position B |
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Absolute Throttle Position C |
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Accelerator Pedal Position D |
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Accelerator Pedal Position E |
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Accelerator Pedal Position F |
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Commanded Throttle Actuator Control |
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Minutes run by the engine while MIL activated |
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Time since diagnostic trouble codes cleared |
Please note that the OBDKey product will work with all OBD-II vehicle protocols.
Please contact us directly for more information: