(WS2) Flash Codes

The task that had to be done was to create a fault with one of the sensors on the engine so that the ECU would log that there is a fault with the the engine. Then we had to bring up the flash codes by checking what sequence the check engine light flashed its codes so that the fault can be found. Fault codes can only be brought up on cars that are EFI (electronic fuel injection) and that have ECU's so that the code can be filed, you could not check fault codes on a car with a carburettor.

A flash code is a fault that is stored in the ECU that the ECU then brings up the check engine light on the dash board. Then you can bring up a flash code, in which the check engine light will flash a certain amount of times this reveals the number of the fault logged in the ECU, you can then bring up the code by. Turning the engine off, then turn the key to ignition then off, then switch it to ignition again, then off, then bring it to ignition again, the codes will begin to flash on the check engine light. The sequence in which the light will flash is it will flash out first number to its value e.g. 3 so the light will flash three times then pause then flash out the second number of the code e.g. 5 so the check engine light will then flash five times so the fault code is 35. Then you would check the manual to see what the code 35 refers to which sensor or which component is giving abnormal readings to the ECU for that code to be logged. Note that there can be multiple fault codes so there could be another pause after 35 and another flash code is given.

Fixing a problem could be as simple as reconnecting a loose terminal however in most cases the part that is giving fault would have to be replaced for example fault code 35 could refer to the TPS (throttle position sensor) and that would have to be replaced. However the other problem could be a faulty wiring within the system so replacing the sensor would not fix anything, this is the many problems that is faced with diagnoses as the ECU tells what sensor or component the fault is with but it cannot tell whether the fault is with the sensor or the connections to that sensor. But before going and checking the whole electrical system or replacing the sensor check the condition of the wires/insulators and terminals for that sensor and see whether they have any corrosion, and check that all the terminals are still connected.

To clear the fault codes you disconnect the battery or the main engine fuse for 30 seconds as this wipes the memory in the ECU then you can reconnect back together. Then check that the codes have been cleared by turning the engine back on and check that the check engine light does not come back on. If it does not come back on then the fault has been successfully fixed. Faults with sensors could cause the engine to run roughly and lower engine performance as the ECU is not getting correct signals from the sensors and this one fault could possibly create other faults that are not filed by the ECU that could make the engine run roughly. After fixing the problem check that all the voltages are within manufacturers specification on all the sensors that where faulty. This is to make sure that the ECU is still correct signals from the ECU and that it will not log another fault.

This how you can bring fault codes on cars with ECU's and the checks that you can do fix the problems and how the codes are cleared after the problem has been fixed so that the check engine does not remain on.



Reference: http://www.gtfours.co.uk/what/fcd/check_eng.jpg (check engine light image)