Help needed diagnosing ECU problem with one cylinder dead

[harrijer]

I should be doing better things on New Year's Eve but here goes

I've been tracking down a problem on my ageing 1997 Galaxy Mk1 2.0i Petrol and need some help:

The beast has suddenly developed a misfire on cylinder 1. Not an intermittent one, the cylinder is contributing nothing all of the time - well at least it makes trouble shooting easier.

So far I have done the following:

Ignition: I pulled the ht cables out one by one to determine the missing cylinder. Each ht lead is producing a healthy spark at the plug end, but just to be sure I managed to swap a couple of leads but nothing changed. I also swapped the plugs, still no change. So that pretty much eliminated the ignition side I think. (Warning: If anyone is thinking of doing the same - be careful with HT leads, I've heard modern ignition systems can produce voltages that can be fatal)

Fuel: Suspecting a dodgy injector, I did and ohms test on each - all the same resistance so they seem ok electrically. Maybe one is dirty or stuck I thought. So, after a bit of googling, youtubeing (https://www.youtube.com/watch?v=YyxSOIO5vQE ,very good) and looking at the wiring diag in my Haynes manual, it seems that the injectors are supplied a positive voltage and then switched via the ecu (computer thingy behind the instrument panel) to ground. So, rigged up a wire probe and stuck one end in the back of the switched side of the injector electrical connector and while the engine was running, started tapping the other end of the probe on the negative terminal of the battery in an effort to simulate the pulsing of the injectors. Hey presto, the misfire was almost gone! It also means the positive supply to the injector is healthy.

Wiring: So why is the injector not switching as we have just proved that it works. I suspected the wiring loom so time to find the other end of the switching wire for the injector to see if it is broken. Had to remove the instrument panel (just the speedo/tach cluster - two screws and a bit of pulling) which revealed the ecu and a big grey multiplug on the side of it. Using a 10mm socket in a small 1/4" drive ratchet, undid the connector holding bolt and the connector came away easily. I found the cable that is connected to the injector on the misfiring cylinder. With the help of a long wire and an ohm meter, I checked the continuity of the cable - it was ok.

So after all of the above - it would seem that the ecu has failed in some way...I think.

Now this is where I would be really grateful for help as I have no experience of ecus. I could rush down the ford agent and buy a new one , but I suspect the price would make me rush out again.

The questions I have are:

1) Does an ecu of this age (1997 seems eons ago) need to be programmed if it has been swapped in from another Galaxy of the same spec?

2) Looking on ebay, I can find several ecus for a Galaxy of the same model and age but the part numbers are close, but not identical. For example, mine is 98VW-12A650-DA and has the letters SCOT on it. Does anyone know if 98VW-12A650- is the crucial bit or do the last two letters matter. It would be great to know I can ignore the last two letters, but I know it's probably wishful thinking

3) Any other ideas of anything I may have missed

Thanks to anyone who has read this far and thanks in advance for anyone who can shed some light on the above.

Happy New Year!

[Mirez]

Sorry to hear of your woes!  I dont have a lot of experience with the 2.0 petrol but itsa ppure Ford engine so at that time the immobiliser was separate so no, you should be able to swap it without much work.
The last two digits generally refer to the revision,  with the ecu that's likely to be the software thats installed.  From experience with Mondeo engines SCOT should be matched

[harrijer]

Thanks for your reply Mirez.

I managed to find a replacement ecu on ebay -  it had the same part number and the letters SCOT as on the original.

Getting the original ecu out was a pain, but probably more so as I've never done it before. Anyway, I plugged in the replacement and then reconnected the battery. This caused the hazards to start flashing but they went out once I inserted the key and turned the ignition on. However, when I try to start the car, it will not start and the driver's door led flashes rapidly. I believe this means that the car does not recognize the key? If I plug the old ecu in, the car starts.

Any ideas? Is there a special procedure to match keys to the new ecu?

Any help appreciated - thanks!

[harrijer]

Sorry, ignore the flashing hazards, that was me!

[insanitybeard]

If the immobiliser lamp is flashing when you try to start up with the new ECU (PCM) fitted that would suggest to me that either the PATS (immobiliser) is integrated into the PCM or the immobiliser module needs to be 'initialised' to the substitute PCM before it'll work. Either way, it'll need plugging in to something that can communicate with the Ford engine management.

[harrijer]

The immobiliser is separate I think. I think it is the box that is mounted just under the PCM/ECU. The fact that I can start the car with the original PCM does suggest that there must be some information stored on the PCM that links it to the immobiliser (or vice versa). So you are probably right.

Looks the idea of swapping PCMs does require some diagnostic equipment. I'll investigate further and post back with any more info I find.