Hi
We have a 2013 Vauxhall Mokka 1.4 A14NET in that cuts out and/or sometimes refuses to start. Seems worse when hot but will also do it when cold. It will crank but won't start. It will then sometimes just start without hesitation and run without any problem, sometimes all day and sometimes only for a short period. There is no injector actuation and non of the coils are being triggered when it won't start. There is a power and ground supply to the coil pack and there is a power supply to the injectors. There is also fuel pressure. There are no fault codes in any of the modules and you can communicate with the engine ecu when it doesn't start. There is also an engine speed reading in live data when cranking and also temperature sensor and all other live data looks ok I think.
I scoped the cam and crank sensors. The cam sensor signal looks normal but the crank sensor signal looks very strange for a hall sensor but I didn't have a known good one to compare. It just doesn't seem to have the same square look to it like a normal hall sensor. I checked it's 5v supply, ground and 5v reference voltage at the sensor and all are present so decided to change the sensor but the fault remains the same.
So if the ecu has the correct engine speed signal and cam signals, why is the ecu not firing the coils and injectors? Is the ecu faulty or am I missing something obvious? Maybe I need to check the power and ground supplies to the ecu next and if there ok maybe have the ecu tested? I'll include the cam/crank waveform, have a look and see what You think.
Thanks. I've never seen the signal before and didn't have a known good one. It just said in ESI that it's a hall sensor, think I jumped the gun a bit fitting a crank sensor as the signal remains the same when it starts and when it doesn't.
If all powers and grounds at ECU are present and the cam and crank signals/sync are good at the module when the fault occurs and there is no pin fitment issue. You could make sure it has the correct spark plugs and coil fitted as in rare cases it is possible that the "noise" created from incorrect secondary ignition components can leak back in to the primary circuit and cause the ECU to do lots of weird things. I would just unplug the cam with it starting/ running and see if can keep running and log a fault code. Maybe do the same with the crank signal and see if it stops updating the scan tool data pid. Other than that I can only think of the ECU being at fault. You could send it to AC tronics for a full test. But there's no guarantee it will act up on there test rig. Some times they find it and sometimes they don't. But they should be able to supply you with another unit which is plug and play for half the price of a new one from the dealer.
It is nice to get a second opinion. If you think it is an ECU and are not willing to make a £1500 mistake you can send it in to them for a simple test fee and it may fail. Confirming your suspicion. But I do agree that it is not a guarantee and I have had faulty repairs from them. But they have always swapped it for a new unit free of charge. They also provide you with another unit which is plug and play meaning you don't need to own every OE spec scan tool. Meaning it IS AN OPTION although not a 100 per cent guarantee. LIKE EVERY THING ELSE IN THIS TRADE. IT HAS IT'S FLAWS.
Lifetime guarantee means if it breaks again they will replace it. Not put it in a box