Technicians are becoming more and more dependant upon fault codes. This is due to the increasing complexity of modern vehicles.
But how do you tackle diagnostic problems without codes.
The first example this week was a non starting Clio 1.4 single point injection.
No communication with the scan tool thus no codes.
Where do you start with this kind of problem?
One of my first tests is power to the injectors, this is a good idication of ECU, main engine relay, & earth are all ok.
In this case we had no power at the injector. The reason is proberly the cause of the non start.
Using the Autodata wiring diagram shown it is possible to work out where the feed comes from. The fuel pump relay, this checked out OK, so the main engine relay was tested, I tend to bridge them as a quick test and after this not only did the engine start but communication with the scanner was restored. Problem solved or was it, I haven't proved how it had failed. It turns out the switched earth signal from the ECU has gone missing, the wiring had gone Open Circuit.
A quick repair restored normal operation, but why had a new ignition coil been fitted in an attempt to get this vehicle going?
The garage had tested for a spark during cranking, not being able to gather codes resulted in a guess. The guess was based on previous experience of this system where coils had been known to fail.
Following a TESTING procedure that I have refined over years of diagnostic testing prevents costly mistakes.
