A recent case on a 2017 Ford Transit 2.0 Ecoblue  with a fault code for a faulty injector circuit. The faults were P126A and P126D on the cylinders 1 and 4 input circuits.

The technician followed the usual process of resistance testing both injectors.

Both passed the test. They moved on to testing the injector loom.

Both looms where load tested from the PCM to each individual injector. All passed the test.

A scope trace was taken of both circuits, and they showed no issues and compared to the other 2 cylinders showed no difference on the scope traces. It was looking more like a software or PCM failure,

The PCM was bench tested and found to be perfect. Confused, the technician began testing all the circuits, one at a time. While this is a labour intensive process, it needed to done to prove no other issues where present.

Then a fault was discovered with the wiring to the MAF sensor. The wiring had already been repaired previously, but 2 wires had broken at the multiplug directly at the terminal pins.

But these broken wires had not logged a DTC, and they had tried several scan tools to eliminate any tool errors, which can sometimes be the case. On repairing the damaged wiring, the codes cleared and the vehicle returned no errors.

This just proves that a fault code is not always proof of the issue, and a methodical test process even though time consuming may be required.

To see or download this article click here.

There are lots more Tech Tips to view, and they are all searchable, on TechTips.ie.

To join the Autobiz Helpline, call 01-905-9500, and then press 2, for further information.