ECU Master Isolator issue

I seem to have developed an issue with my ECU Master battery isolator. I have a repeatable issue where if the RPM is steadily increased, at approx. 6300rpm the entire car shuts off and will only power back on if the internal isolator switch is cycled off then back on again.

I have checked the wiring to the the isolator and both switches and all is as it should be so I’m at a loss as to what it could be.

I have replaced the battery just in case also.

Strangely, if you quickly raise RPM it will go past 6300rpm without issue but any steady increase results in the car shutting off!

Anyone any ideas?

Link of EMU Black log below if it helps.

Battery voltage looks good, I was thinking maybe it was too high.
Don’t see any red flags in the log on the first look…

How is the isolator, switches and ecu/ignition coils grounded?

In the log the quick blips only get to around 6000 where the cut off events occur at higher then 6300, can you get a blip higher and just didn’t log that? looking at just the log it seems like it occurs past 6300 rpm.

What does you CAN bus look like? is there any devices that could be sending a shutdown signal at the incorrect time?
You can try disabling the CAN kill message, the EM switch and changing the shutdown times for the power save and EM switch to help diagnose if its an issue with either of those two circuits.

No CAN messages to cause shutdown, car uses PMU, ADU, EMU black, GPS and isolator all from ECU master.

Battery saver function disabled.

Isolator is grounded to chassis, using the same point as where the battery is grounded.

I’ll grab another log later today if weather permits with higher rpm pulls and post a link to it.


Link of new log all be it short, is below. Its as much as I can do without multiple runs up and down the short private road I have here.

Issue is very repeatable. Also notice the DBW error pops up at higher rpm.

Any insight you can give is appreciated.

In case it helps matters i have attcahed links to PMU, ADU, EMU projects and the GPS and Isolator configs.

How is the power save switch and em switches grounded?
Ignition coils are grounded to the head and so is the ecu? I am asking for EMI related reasons.

I’ll assume at this point you’ve gone and checked all your grounds are clean and tight; battery to chassis, block, ecu, ignition coils, power save and em kill switches, pmu etc.

Looking at all the files and logs now, I’m seeing the dbw error blips but no apparent cause. I wish we could log at a higher frequency then 25 Hz as I think there’s dropouts happening that I can’t see in the log…

I also saw your facebook post and I’m choosing to respond here and there’s too many ‘you’ve lost trigger sync’ comments from people who don’t know what a power cycle looks like on a log lol, I’ll get lost in the sauce.

Only thing I think I could wish for otherwise is a log of the PMU, and things like the turn off signal and battery voltage logged at 100hz…

I see you have the power save at 5 seconds on the battery isolator, try the same on the em kill and see if that makes a change. or even disable the em kill input
I would also add the CanX file for the battery isolator and log that at a high rate as well, it can tell you why the battery isolator is turning off.

I have had recently a battery isolator fail, but it was under cranking not randomly at rpm. Have you contacted ECUmaster tech support about this yet?

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Firstly, thank you again to the reply.

Power save and EM switches are grounded to chassis.

ECU currently grounded to chassis, but I can change to head easily as there are spare filler wires terminated to Deutsch connector in the engine bay.

Coils grounded to head. All earths are good.

Echo the thoughts on FB! Sometimes it’s worth a shot though.

I will do another short drive with a few higher rpm blips and a steady acceleration, during which I’ll save the log from the PMU.

I’ll also add the CANX file of the Isolator.

I haven’t as yet tried UK ECU master tech support as in the past I have found them somewhat unhelpful for the most part.

Sorry for the late reply. I suggest to check the reason of shutdown in Light Client. You can find there a table with Flags category, it should be something there if you rev up to 6300 RPM. Active flags would have “1” value.
Of course you need to receive CAN frames from Battery Isolator in Light Client during the trial.

So a quick update to the isolator issue, after some checking of settings etc. It was suggested by a few that the EMU’s inertia switch may have been the issue.

Deactivated the Inertia switch in the PMU software and it would seem the cutting out issue has been resolved. Which means I will alter the mounting of the PMU to utilise rubber bobbins and hopefully eradicate the issue.

Another test drive and log tomorrow to check the issue is resolved.

STILL have the dbw error though, hopefully can resolve that by soft mounting the DBW to the manifold.

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As a further update after various road tests over the past few days and today a dyno session. I have FINALLY resolved both the cutting out issue and the DBW fault.

Electrical shutdown issue
This turned out to NOT be the isolator, it was the Inertia switch triggering in the PMU! It appears it was due to the harmonics of the engine and the fact the PMU was hard mounted. First I disabled the Inertia switch and the issue was resolved, I then mounted the PMU on rubber bobbins and re-enabled the inertia switch and the issue remains resolved!

DBW Error
After some research it seem the issue of harmonics causing issues with DBW throttle bodies is a well known issue on K24 engine (at least in the USA). To try and resolve i orderd some billet adpaters so that i could “soft” mount the DBW to the manifold by using 2 adapters and a short section of silicone hose. DBW fault now gone and the DBW position follows the DBW target until redline like it should rather than beginning to close above 7400rpm like it was doing.

Hopefully this fault finding saga may result in others having a quicker fix for similar problems!


glad you finally got to the bottom of it. good work

As am I. Was very frustrating!

Hopefully others may avoid encountering the same fault finding journey I had to go on.

Great work solving that!

Is your engine solid mounted? I know 4 cylinders are typically bad for vibrations but curious if there’s any other contributing factors to the dbw issue

Thank you. The engine has very minimal movement so almost solid mounted.

All the ECU master electronics were solid mounted to the chassis (other than GPS module of course). Now all are mounted on rubber bobbins to prevent any issues with vibration.

Such a frustrating journey but glad it’s now resolved!