OBDII : Read your car’s mind

ALYS TechTalk Series
written by: Sherif Aly

Introduction

The development of body electronics in modern cars is getting more and more ambitious, this is because the number of control units and the functionality included in the control units are both increasing and the innovation rate is speeding up.

Features that used to be found only in luxury cars are standard today in mid-range cars; this trend is bound to grow stronger because of shorter car life cycles and customers expecting innovations in low-end cars.

These engines need sophisticated test equipment to diagnose faults and system failures. Ineffective diagnostic work inevitably leads to vehicle problems, dissatisfied customers and labour costs.

To facilitate car diagnostics, car manufactures added an On Board Diagnostic (OBD) , a computer that captures information about how the car is running.

What is OBDII

On Board Diagnostic (OBD) is a computer that captures information about how the car is running. The data tracked by the OBD II system was originally intended to monitor the engine's emissions and track down problems that caused cars to pollute more than normal.

Today, however, manufacturers have extended the standard to contain a great deal of data about problems and performance, OBD II data is what causes your car's "check engine" light to go on when there is a problem

All vehicles released after 2005 contain OBDII. OBDII is version 2.0 of the standard for communicating this information.

The OBD connector must be located within 3 feet of the driver.

Pin 2 - J1850 Bus+
Pin 4 - Chassis Ground
Pin 5 - Signal Ground
Pin 6 - CAN High (J-2284)
Pin 7 - ISO 9141-2 K Line
Pin 10 - J1850 Bus
Pin 14 - CAN Low (J-2284)
Pin 15 - ISO 9141-2 L Line
Pin 16 - Battery Power

What is CAN

Controller Area Network (CAN) is a serial network that was originally designed for the automotive industry, but has also become a popular bus in industrial automation as well as other applications.

The CAN bus is primarily used in embedded systems, and as its name implies, is the network established among microcontrollers.

OBD through CAN

When connected to the CAN network thought the OBD connector, we can start receiving OBD data, the OBD II port allows your car to report three kinds of information: Diagnostic Trouble Codes (DTCs), real-time data, and freeze frame data.

Diagnostic Trouble Codes (DTCs) are simply error codes that can be looked up to determine what problem your car is experiencing.

– For example, the DTC P0302 means "cylinder 2 misfire detected".

Real-time data is the raw sensor data reported to the OBD computer.

– This data can be helpful for troubleshooting problems and monitoring engine performance.

Freeze frame data is a snapshot of the real-time sensor feeds at the time of a DTC condition.

- An auto mechanic can use this data to figure out what was going on at the time your car's "check engine" light went on.

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