Check Engine Light

When your car developes a wiring or electrical problem ( see above image ) or your Check Engine Light comes on it may not be as serious as it looks. Some faults do not cause the Check Engine Light to come on however a fault code or codes could exist in the computer (ECU) or sensors which can help diagnose the faulty component or wiring.

At CarDiags our test equipment covers low voltage (5 volt to 30 volt) DC systems and can be used on cars, vans, lorries, motor bikes, quad bikes, boats, caravans, trailers and many more.

Remember, we come to you at home or work and our initial diagnostic time is at a fixed cost.

Since the late 1990's most motor vehicles have become more electronic with mini computers and sensors installed which control a lot of the functions such as engine spark timing, fuel injector pulses, automatic windscreen wipers etc etc. These controllers are linked to a central computer ie: ECU. This warns you of a problem by turning on the check engine light as shown above.

Vehicles are fitted with a diagnostic plug which a technician can plug an electronic tool which can reveal what caused the Check Engine Light to come on. Many garages do not have the necessary equipment to correctly diagnose the fault and simply replace components in the hope it will go away.

Often a garage may miss diagnose this as a faulty component which can prove costly to you especially the main computer (ECU) and may only resolve the problem short term. There could be several reasons for this warning light to come on.

Our testing can include motorcycles, quadbikes, motor boats, basically anything with 12 to 48 volt systems.


As a vehicle gets older, water and road salt ingress can cause corrosion in wires around connections which causes resistance to voltage. The computer (ECU) see this as a faulty component and therefore causes the Check Engine Light to warn you of a fault. With the correct equipment this type of fault can be detected and corrected making considerable savings to you.

Parasitic draw.

Is your battery going flat overnight or after a few days. Well thats when parasitic draw comes in. Its basically some circuit in the vehicle drawing current from the battery after everything is switched off. This problem can be quite difficult to find especially with modern cars that have multiple computers and sensors. Our tools can identify where the problem lies saving considerable time and money replaceing modules etc when it could be a simple wiring problem.

OEM Parts.

When a garage diagnosis results in new parts being fitted, often they will use non factory parts instead of OEM (Original Engine Manufacturer) parts. These may be cheaper than original (OEM) parts however they may well be inferior or of less quality. This can therefore only be a short term fix and may be the cause of the Check Engine Light symptom. Perhaps you bought a second hand vehicle, you may not know its history or what new or second hand parts have been fitted to it.

Battery failure.

Be aware if you are having poor starting problems or no starts it is likely that your car battery is failing. It used to be a simple matter of fitting a new battery however that has all changed since 2000. Firstly if the battery is simply replaced you will lose your radio code and any computer components will reset to there factory settings so the car may not drive like it used to. More modern cars have battery management computers so not only will you lose settings but the battery management system will retain its settings for the faulty battery which will mean the new battery not being charged correctly. A good competent garage will fit a small battery backup to your car first before changeing the battery which means your radio and personal driving settings will be retained.


Sometimes garages / owners may fit additional equipment to the vehicle and not carry out the fitment correctly. It may work however there may be an underlying fault which only shows up later in life.


Did you know that modern vehicles can have up to ten keys registered for the vehicle. The computer (ECU) registers every key uniquely so you may not know when buying a vehicle if you received all the keys registered. We can see this information and deregister any keys not present. This will safeguard your vehicle from being stolen, usually, just after its purchase.

Parts cannon ??.

This is a term used in the motor trade when diagnostics are not performed correctly or not performed at all. What this means is that in stead of performing a proper diagnostic AND WIRING check the mechanic simply fits new parts which he / she might think will cure the problem. As this fails to work more parts are fitted until, hopefully, the problem is solved. This is a very expensive way for you, the customer, to fix a problem which if diagnosed correctly may only cost you a few pounds in fix time.

Buying a used vehicle.

It is always wise to take a vehicle technician with you who can check the vehicle over to reveal information about it that may not be visible to you. This information could affect your decision or buying price.

Boats and fibreglass vehicles.

Boats and other fibreglass vehicles must provide a seperate lead for chassis ground. We can check easily power and ground issues with our equipment. This will save you time and expense trying to locate the fault. Remember diagnosis is a fixed fee - what you decide to do is upto you.


With the right diagnostic equipment all of the above and more can be detected and corrected saving you costly unnecessary repairs or replacement of expensive components. The fault codes may be historical and have never been cleared so these too can be reset.
Diagnosis of the vehicle is relatively inexpensive and should be the first call for action.

You might find this video interesting although its from the USA it applies around the world. I have had personal experience of this with my vehicle when it was recalled for an airbag issue but the dealer reported a suspension problem. That was 4 years ago and 4 MOT's passed. !!

Please note this video has advertising links which have no benefit to us whatsoever. Worth watching

Back to top

Please call 0191 5808188 or mobile 07803 602975 to arrange a visit with a fixed diagnostic fee and free quotation for repairs.

Call any time Mon - Fri 10am til 6pm Sat-Sun - 10am til 4pm incl. Bank Holidays

or email us HERE

Cash, credit and debit cards or bank transfer accepted.

Visa debit or credit card mastercard debit credit card solo debit card Maestro credit debit card

Back to top

Website created by CUT 8 Designs.

All material is copyright (2021) and may not be copied or used in any form without prior permission.

Privacy and Cookie Policy