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Auto Diagnostics Help Guide

We receive a lot of emails per day asking different auto diagnostic questions. We have compiled this list of commonly asked questions regarding auto diagnostics in the hope it will answer your burning questions and make the world of auto diagnostics an easier thing to understand. Have a question regarding auto diagnostics? Email us.

How can i reset my airbag light?

There are several reasons why your SRS or airbag light is illuminated on your dashboard. Firstly we would advise you to check all visible connections under the seats, and think about any work which may have been done in or around where the airbags are situated, as there could be a loose connection or a broken connection. If you are not able to find any problems with the connection, you will need to buy a suitable airbag reset tool. An airbag reset tool will read and talk to the airbag system within the car and automatically find where the fault/error is coming from. The airbag reset tool will also reset the light on the dashboard.

How do i find a fault code?

In order to find a fault code which has been stored in your vehicle memory you need to use a fault code reader. A fault code reader will talk to your vehicle and read its inner thoughts. The scan tools work in the same way in which a vet would try to find the problem in a sick animal, it will asses each and every part of the animal until he/she finds the problem, when the animal cries the vet knows that a problem has been found, in the real world our vehicle will spit out an error code. An error code will look something like this P0098, P0763 or P0756. Although the error code will not always tell you exactly what the problem it, it will give you an indication or where to start looking. Once you have found your DTC (Diagnostic Trouble Code) you will need to cross reference it with the fault code library supplied by Dominator Auto Diagnostics.

How can i reset/remove my ABS light

If your dashboard displays the ABS light (as found in the dash light directory) the chances are it will be one of two things that need to be replaced. The cheapest is the ABS sensor, but seeing as your vehicle will have 4 of these (one on each corner) you need to figure out which one needs changing - and believe us, it can be very tricky to change an ABS sensor as they can sometimes seize - so we would advise you use a code reader which can read the ABS system. The Autel MD range of code reader will do just that. You can find the Autel MD range in our professional diagnostics section. Once you have found out which sensor needs to be replaced head on over to www.bavariandominator.co.uk. The second and more expensive outcome is that you will need to replace the ABS module. We would reccomend you pick one up from a breakers yard.

What is this dashboard light?

If you have a dashboard light and are not sure what it means - look no further than our dash light directory. We have pictures & videos for most dash lights & dashboards on the road today. In most cases the dash light can be found in the vehicle operating handbook, but these books are always easily misplaced or lost by current/previous owners.

Head on over to our dash light directory for further help.

What is a diagnostic protocol?

Info coming soon.

Please explain auto diagnostics to me

Info coming soon.

What does OBD mean?

OBD stands for On Board Diagnostics. OBD is a self diagnosing vehicle fault system. It was introduced in the 1980's but at first was very basic, nowhere near to the OBD systems that are available to us today. Early OBD systems were only able to show a malfunction indicator light or MIL, but not able to give you a hint of where to start looking for the problem.

What does OBD2 mean?

OBD2 stands for On Board Diagnostics 2. This is an improved version of OBD and as such offers more information relating to problems with the vehicle. An OBD2 port has a 16 pin female terminal, and suitable code readers have 16 pin male connectors. One of the 16 pins on the connector supplies power to the code reader so there is no need for a seperate power source for the scanner.

The code reader will produce a DTC (diagnostic trouble code) which will  consist of 4 digits and are fronted by a letter. The letters are P for engine or transmission (powertrain), B for body, C for chassis and U for network. 

What does EOBD mean?

EOBD stands for European On Board Diagnostics. The EOBD system is essentially the same as the OBD2 system, using the same 16 pin SAE J1962 connector. EOBD was made mandatory from 2001 for all petrol cars carrying upto 8 passengers, and from 2004 for all diesel cars.

EOBD fault codes are made up of 5 digits, a letter followed by four numbers. When the fault code shows up the letter will relate to a certian module within the vehicle. The next character will be a 0 if the system complies with the EOBD standard. So it should look like P0xxx.

The next character would refer to the sub system.
P00xx - Fuel and Air Metering and Auxiliary Emission Controls.
P01xx - Fuel and Air Metering.
P02xx - Fuel and Air Metering (Injector Circuit).
P03xx - Ignition System or Misfire.
P04xx - Auxiliary Emissions Controls.
P05xx - Vehicle Speed Controls and Idle Control System.
P06xx - Computer Output Circuit.
P07xx - Transmission.
P08xx - Transmission.

The following two characters would refer to the individual fault within each subsystem

What does SRS mean?

SRS stands for supplimental restraint system. It is basically the airbag system. If your airbag light or SRS light is illuminated, it is clear there is a problem with the airbag system. The code needs to be reset and airbag light removed from the dashboard with an airbag light reset tool.

What does CAN-BUS mean?

CAN-BUS stands for Control Area Network and can be used to connect to automotive systems such as transmission, airbags, antilock braking/ABS, cruise control, electric power steering/EPS, audio systems, windows, doors, mirror adjustment, battery and recharging systems for hybrid/electric cars.

What does EML mean?

EML stands for Engine management light. Here you will see a video of the Engine management light. To find out why your EML light is showing on your dashboard you need to get a code reader to read the codes.

What does DTC stand for?

DTC stands for Diagnostic Trouble Code. Once you plug your car upto a code reader or scanner it will display a dtc if there is a fault. The dtc will consist of 1 letter then 4 numbers for example P0016 - which will give you a better understanding of where the problem is.

How do i change car mileage?

Mileage correction is quite often a very tricky procedure, and rarely are you able to just plug a mileage correction kit into the OBD2 and select the new mileage. It often involves interrogation of the ECU. For a full range of mileage correction tools please visit our mileage correction page.

My ABS light is showing, what does this mean?

If you ABS light is showing on your dashboard it could be either an ABS sensor which needs to be changed, or the ABS module which needs replacing. The ABS sensor is the cheapest fix and you can get them from Dominator Auto Diagnostics. If you need a new module we would advise to pick up a replacement from a breakers yard as they can be quite expensive brand new. You might need to pick up a code reader to find out which ABS sensor needs changing.

What does the EML light mean?

The EML light on a BMW stands for 'Elektronische Motorleistungsregelung' - which in English is loosely translated to 'Electrionic Engine Power Control' and relates to the drive by wire throttle control system.

My engine light is showing, what does this mean?

The engine light alone will not tell you what the problem is. The engine light illuminates simply to tell you that theere has been a malfunction somewhere within the engine system. You need to hook the vehicle upto a code reader via the OBD2 port. The code reader will read out an error code which relates to a specific part of the vehicle. Once you have read the code with your code scanner, you can find out what it means by visiting this diagnosic trouble code library

How do i reset my oil service/inspection light?

On some older cars you may be able to reset the service lights or oil inspection light just by using the buttons on the dashboard, but for most cars on the road you will need to use a service reset tool.

I have intermittant car trouble, how can i fix it?

If your car is experiencing intermittant problems, that is to day it will have a problem one day, and not the next - it can obviously be difficult to find out what the problem is - it may be difficult to explain it to the garage, or you might be worried about taking the car to the garage because the car might be working fine that day. In order to find out where and when the fault is occuring you can use a live data recorder which will record car data, in the same way an aircraft black box records aircraft data. Live data recorders are inexpensive. The recorder fits in the palm of your hand and simply plugs into the OBD2 port, you leave the recorder plugged in for a few days then remove & review the data. A great tool.

What is Freeze Frame Data?

Freeze Frama Data sounds more complicated than it actually is. Basically when a diagnostic trouble code is triggered within a vehicle, a code reader with freeze frame data capability such as the Launch CRP129 will take a snapshot of the different modules and systems within the vehicle when the fault code was triggered. Watch this video which shows the Launch CRP129 (VIII) displaying Freeze Frame Data after a fault code was triggered.
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