FAQs
Help Centre for Electrical Wiring Repairs
WHAT ARE "FAULT CODES"?
Apart from some very early electronic fuel injection systems almost all computer controlled systems in cars have some system for detecting faults built-in, these faults once detected can be read out as fault codes.
HOW ARE FAULT CODES DETECTED?
Apart from some very early electronic fuel injection systems, almost all computer controlled systems in cars have some system for detecting faults built-in. Faults, once detected, can be read out as fault codes.
WHAT IS A DIAGNOSTIC COMPUTER?
A Diagnostic Computer is a service tool, sometimes a stand-alone unit, sometimes based on a laptop computer that is connected to the cars diagnostic connector. The Diagnostic Computer is used for the purpose reading fault codes, live data etc.
WHAT IS "LIVE DATA"?
It is possible with most modern engine management systems to read out the actual values for the sensors that feed the computer. By examining the information it is frequently possible to identify problems that the fault codes system may not spot.
ANOTHER GARAGE RAN A DIAGNOSTIC, THEY SAY THERE’S NOTHING WRONG BUT STILL MY CAR DOESN’T RUN PROPERLY, WHY?
Just because there are no fault codes it does not mean there is nothing wrong, there may be a fault with a sensor for instance which causes it to give a plausible but wrong signal. An examination of live data from Response Diagnostics would reveal any issues quite quickly.
WHAT ARE ADAPTATION LIMITS?
More modern engine management systems are capable of learning the characteristics of the engine that they control. These learnt values are stored in the on-board computer's memory. Once again these values are compared with preset limits and if they are exceeded the computer relays a fault code.
MY CAR FAILED ITS MOT ON THE EMISSIONS DOES THAT MEAN THE LAMBDA SENSOR SHOULD BE REPLACED?
Not necessarily, further tests would need to be completed to determine if the problem was somewhere else in the system.
Frequently there is another fault in the system and although the sensor is reporting this correctly the ECU can only make adjustments over a certain limited range.
CAN YOU JUST RESET MY ENGINE LIGHT?
Of course I can, but if I don’t find and fix the underlying problem there is a very good chance you will back in a very short time.
