ECU replacement advice.
 

Hi Folks,
Looking for a bit of advice. My understanding is the engine ECUs should be replaced as a pair and they need coding to the car via a PIN, is this correct?
My slave ECU is reporting a miss fire (and it is correct), the injector has been replaced and the wiring checked so can I just replace a single ECU?
I have had the ECUs tested and no problem was found however, they could only test the components and not the functionality in a simulated driving scenario.
Car is 2004.

16592 - Injector: Cylinder 8 (N86)
P0208 - 004 - Circuit Malfunction - Intermittent

This feels heavy handed. I would be looking into the code. Circuit malfunction is vague.

We've replaced the injector, checked the wiring from the ECU to the injector so I don't see what else it can be.
Any ideas are welcome.

In my humble opinion, doubtful that the ECU is the culprit. Proceeding in this direction could be a costly endeavor resulting in no change. There are others on the Forum that are familiar with this type of challenge.

A description of how the car is running or any other symptoms might help.

Often misfires on the early B's leads to a vacuum leak. The question here is since it's only one cylinder that kind of rules it out? However, since it's a 2004 a smoke test wouldn't be a bad idea none the less. Better yet if there's a history of the vacuum lines being replaced that's wonderful.

How did you check the wiring?

OK so here we go... While we had continuity on the switched earth from the ECU and we had a positive feed to the injector which indicates the wiring is fine, upon further investigation it was found the insulation on both wires to the injector had split so the problem was down to the wires shorting together within the wiring loom causing the misfire. This was found by the fantastic guys at Phantom Motors in Crondall.
The reasons for suspecting the ECU are two fold, it has had water ingress at some time and it has faulty written on it by someone in it's past history.