In the heat of the fault

Hannah Gordon changes hats this month, and tells us how she solved an interesting fault

Published:  02 November, 2018

At the workshop we cover all kinds of vehicles, old, new, big and small but with all these vehicles we need up to date diagnostic equipment to be able locate faults within the electrical system.
    
In the workshop this summer was a 2009 Volkswagen Golf that had an intermittent issue which meant the car would go into limp mode, the cruise control was disabled and the climate control wouldn’t work. Understandably in the weather we were having the lack of air conditioning was a major concern to the customer. No one wants to be without air conditioning in 30Cº.
    
I plugged in the trusty diagnostics reader and came up with four faults. These included turbo boost sensor, manifold pressure, throttle pedal position sensor and ‘fuel system
too rich’.
    
In my experience cars can throw up all kinds of trouble codes even when there is no issue with that part. I wouldn’t say some manufacturers are more troublesome than others but if a light does appear on the dash it’s best to get it checked out as soon as possible.

Issues
I cleared the fault codes and told the customer to see how it drove and if the issues resolved themselves. The customer had the car for just an hour before they called and said that the problem had reoccurred, as much as this is a pain for the customer I always clear the faults and see if it happens again rather than changing unnecessary sensors. I got the Golf back into the workshop and once again plugged the computer in, which brought up one code. This was the throttle position sensor. A quick call to VW and a discussion with their parts people showed that this particular issue can lead to the cruise and climate control not working.
    
Next day delivery on the part means the car came back in the following day. One bolt, two plastic clips and an electrical connection later and the pedal was off. Gone are the days of the throttle cable. The throttle response is now done by a sensor on the pedal which works out how far the pedal is being pushed and tells the engine how to respond. It is clever stuff,  when it works.
    
A pedal replacement on the Golf only takes five minutes and another clear of the fault code before taking the car for a road test. On the test drive cruise and climate control were checked as well as making sure no dash lights had appeared.
    
Modern mechanics have become very computerised. Dash lights appear whether it is indicating an issue with the airbag systems, ABS or engine and diagnostic computers are so important to narrow down what the issue could be. I dislike the reliance that some workshops put on just trusting what appears on the screen of the diagnostics. It is still imperative that mechanics test sensors and look into live data to make sure that unnecessary components are not replaced and the costs put onto the customer, who will have to pay.


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