Diagnostics and Vehicle electronics


Diagnostics for Paulton, Midsomer Norton, Radstock and the Bath and Bristol area.


Do you have an Engine management, DPF, ABS/Traction control, SRS/Airbag light on?, we can diagnose and repair these systems and more.


Here is a list of some other electrical and mechanical fault diagnosis that we offer.

  • DPF (Diesel particulate filter)
  • Petrol Catalyst
  • Petrol and Diesel injection
  • Manual and Automatic Gearbox inc (DSG) repairs, servicing and electronics
  • Wiring and ECU
  • Body control functions (windows/wipers/lights etc)
  • Reprogramming and calibrations


There is a great misconception that to diagnose a fault, all that is required from a technician is to plug a diagnostic machine into the car and that it subsequently shows the fault codes telling us what to replace. This is extremely misleading.


The following pictures and subtext are of us diagnosing a misfire on a VW Golf, from this we hope to give you an insite into how we diagnose and rectify faults. 


Hopefully this will help elaborate on the diagnostics side of the workshop and how we aim to confirm what is needed to be replaced before any parts are changed.



Firstly we scan the vehicle to gather any dealer fault codes stored in the cars memory. We can see the car is suffering from a misfire and the ECU has issued codes to match.

We can see that there is in fact a misfire and that the car is able to identify it as being number two cylinder. This can be confirmed with the use of the data and graphing functions of the scanner. These are readings of sensor feedbacks and calculations from the ECU.

There can be a number of reasons why a cylinder might be misfiring; from a common spark plug fault, to a fueling issue or low compression for example.

Firstly we use the oscilloscope to check all cylinders, this is to make sure that the ECU has issued the code for the correct cylinder.

From our knowledge of graph reading and the use of voltage and amperage scopes, we can analysis the data and confirm that the misfire is caused by a faulty ignition coil.


Ater changing the Ignition coil and spark plug (O.E spec) on cylinder two, we can then reuse the oscilloscope to confirm that the fault has been rectified.


We then go back to the live data where our technicians can see that car is no longer suffering from the misfire and all counters are on zero.  


After a road test, we re-scan the vehicle to confirm that there are no returning codes, and that all the onboard readiness monitors have been passed.




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Central Garage (Paulton) Ltd

Ham Lane



BS39 7PL


Tel: 01761 416465 01761 416465

Tel: 01761 413374


Opening times

Monday                8am-5.30pm

Tuesday               8am-5.30pm

Wednesday          8am-5.30pm

Thursday              8am-5.30pm

Friday                   8am-5.30pm

Saturday                   Closed

Sunday                     Closed


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