OBD-II Codes Frequently asked Questions

1.    How do I check which Protocol I need?

It is possible to check which protocol your vehicle is using by checking the OBD2 connector on the vehicle.


Must have pin 7 and pin 15 in use.


Must have pin 2 and pin 10 in use.


Must have pin 2 in use.

Note: Pins 4, 5 and 16 are also used for power and signal earth.


OBD2 plug

2.    Where is the OBD2 connector in my car?

In order to be OBD2 compliant the Diagnostic Link Connector ( vehicle connector ) must be sited within 18 inches of the steering wheel ( in practice it is usual found under the dashboard  directly under the steering wheel or alternatively it is mounted on the central console under a cover.  

3.    What does interface protocol mean?

The interface protocol is the electrical standard which the interface unit uses to “talk” with the vehicles computer ( ECU ) via the Diagnostic Link Connector ( DLC ). There are 4 main protocols at present ISO,PWM,VPW plus 3 variants of  CAN-bus.

4.    What is EOBD?

It is the diagnostic standard for the European community, however it is based on the American OBD2 standard and in practice they are very similar. 

5.    Why hand- held OBD tools?

In some ways they are do have an advantage, they are small and robust  and are totally standalone, they cover all three protocols ( ISO,PWM and VPW ).  However they do not have the same capability as software based systems and are specifically aimed at fault diagnosis, DTC retrieval etc ( see our shop for a more detailed description).

6.    What is CAN-bus?

CAN stands for Controller Area Network and is a communications protocol like ISO, PWM or VPW.  CAN-bus overcomes the main problem of the other protocols of slow speed, and as such is better suited to future OBD2  requirements. It will become the standard electrical interface for vehicles in 2008, however some manufacturers began using it on 2004 models.  

7.    Computer interface problems?

There are several reasons why the computer may not talk` to the  serial output of the interface.

a.  The COM port maybe incorrectly set, correct settings are:

Bits per second:  9600
Data bits:  8
Parity:  None
Stop bits:  1

b.   If using a USB to serial converter not all are compatible check they are OK regarding operating system, RAM size etc.

c.  Some laptops have an Ir port this may need to be disabled to avoid conflict between ports

8.    What is OBD and what are its benefits? 

OBD stands for “on-board diagnos­tics,” a computer-based system built into all model year (MY) 1996 and newer light-duty cars and trucks. OBD monitors the performance of some of the engines’ major compo­nents, including individual emis­sion controls. The system provides owners with an early warning of malfunctions by way of a dashboard “Check Engine” light (also known as a Malfunction Indicator Light or MIL, for short). By giving vehicle owners this early warning, OBD protects not only the environment but also consumers, identifying minor problems before they become major repair bills.

For example, by identifying a relatively inexpensive repair like the replacement of a malfunctioning oxygen sensor, OBD can save the owner the cost of replacing the catalytic converter later. By helping to ensure that the vehicle operates within its original design specifica­tions, OBD can help save con­sumers money by making sure gaso­line isn’t wasted as a result of, for example, a loose gas cap or incom­plete combustion. OBD stores infor­mation about the malfunction detected and actually helps the repair technician to diagnose and fix the vehicle. When OBD checks are performed as part of a state’s Inspection and Maintenance (I/M) program, they can help save con­sumers time, taking on average five minutes or less in centralized pro­grams.

9.    Can the OBD system be repaired, deactivated, or modified?

The rule of thumb when it comes to emissions-related vehicle repair is that any modification that changes the vehicle from a certified configuration to a non-certified configuration is considered tamper­ing: this applies to both vehicle owners and repair facilities and is therefore a Federal offense. Replacing a catalyst with a straight pipe is one traditional example of tampering. Likewise, overriding the OBD system through the use of high-tech defeat devices, non-certified computer chips, etc., would also be considered tampering. The OBD system may, however, be repaired back to its original certi­fied configuration with certified “performance chips” or appropriate aftermarket parts.

10.    Will the repair be covered by warranty?

Warranty coverage varies depend­ing on components and individual manufacturer warranty provisions. In most cases, however, responding sooner rather than later is likely to minimize the individual owner’s repair liability. The CAA requires an 8 year or 80,000 mile warranty on the major emissions control components such as the catalytic converter, and a 2 year or 24,000 mile warranty on other emissions control components.

11.    Q: What is CAN and why is it important?

A: CAN stands for Controller Area Network. CAN is a new means of communicating with the can for diagnostics used by the latest generations of VW, Audi, SEAT, and Skoda vehicles. Unlike the older ISO9141 system which used a single K-line for diagnostic communications, the new CAN-Bus system uses a twisted pair of wires with differential signaling. CAN-bus is considerably faster than ISO-9141 (500 kpbs vs. 10.4 kbps). Both new hardware and new software are required in order to communicate with cars using CAN-bus for diagnostics.

12.    Does VAG-COM work with cars that require direct CAN access for diagnostics?

Yes! We have integrated CAN compatibility since the Release 404.0 version of VAG-COM, but as CAN uses different hardware, new interfaces are required in order to communicate with a CAN-based car. These are now available as well. The new HEX-COM+CAN and HEX-USB+CAN interfaces are fully compatible with the new latest cars which require a direct CAN connection.

13.    Do the CAN-Bus Interfaces also work with older vehicles that use the k-line?

Yes! The HEX-COM+CAN and HEX-USB+CAN are fully backwards compatible with older vehicles that use either single or dual K-lines as well, so they work with all VW/Audi/SEAT/Skoda from 1996-2005.

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