2018 G21-Injector Short to Ground

[nathandantzler]

2018 G21 with PCM H5.

Bought the boat and took it out for the first time. Ran great for about 20 minutes, then suddenly started throwing these codes:

• DTC 2261

• DTC 2270

• DTC 2276

• DTC 2279


All are “Direct Injector High Side Short to Ground” on cylinders 1, 4, 6, and 7.

The engine runs very rough, but will occasionally spike back to normal RPMs and then go rough again. I had to limp it back to the dock at about 1200 RPM.

Has anyone seen this issue on the H5 before? Any advice before I start pulling the intake manifold to trace wiring?

Thanks!

[jpwhit]

Short to ground code really just means the high side of the injector isn't at the voltage expected. It doesn't actually have to be a short to ground. Given the pattern of which injectors are giving that code, I suspect it may be something like a fuse or relay on the power feed side of those injectors. Unfortunately, without a wiring diagram or being able to physically look at the engine, that's all the help I'm able to provide.

If I were diagnosing this further, I start with a meter or scope looking at the powered side of the injector wiring, and then tracing that wiring path to the voltage source. You can also check the injector that are working to see which wire is the powered side and which wire is the sink side wire going to the ECM. The way the ECM detects this code, is it watches the voltage of the sink side input on the ECM to see if the voltage rises when the sink FET is turned off.

[nathandantzler]

Thank you so much for taking the time to respond — this is exactly the kind of guidance I needed and really helps point me in the right direction.
Based on what you said about tracing the power feed side, my plan is to start with the fuses and relays first since that’s the most accessible starting point. If that doesn’t turn anything up, I’ll move on to pulling the intake manifold to get eyes on the injector sub-harnesses underneath. I know that’s a bigger job but it sounds like there’s no way around it if the fuses and relays check out clean.
One thing I did find while I was poking around — I pulled the ECM connectors and found what looks like green corrosion on one of the pins inside one of the connectors. I’m attaching a photo. I don’t know if that’s related or just a separate moisture issue, but it seemed worth mentioning given the symptoms. Curious if you think that could play a role in what I’m seeing.
I’ll report back once I’ve had a chance to dig in further. Really appreciate your help — this community is invaluable

[nathandantzler]

I was able to get a wiring diagram from PCM and confirmed pin 72 controls the High side injector / fuel pump relay.
As part of the troubleshooting, and for future repair work, I created an HTML website that maps each pin of the ECU to its component and vise-versa.
I thought I'd share that here so others can use it as well.
https://pmc-h5-h6-wiring-tool.netlify.app/

[nathandantzler]

I had a very small amount of corrosion on pin 72 of the ECM, after building that app linked in my last reply, I realized that pin controls the fuel pump and high side of the injectors.
i cleaned it and all appears to be working again with no faults.

As a preventative measurement to make sure nothing else is going on, I also removed the upper intake manifold cleaned every single electrical connection (Dioxit and dielectric grease).

[bturner]

Great write up and thanks for posting the fix!

[Scooter G]

That Map is very impressive, skills I don't have! You've got some time into that, for sure.

[DoubleUpDisaster]

Wow, thank you for sharing that with the community!

[nathandantzler]

I took the boat out today and it ran great for about an hour then “Injector High Side short to ground” DTCs returned, this time cylinders 6&7and “injector short or open ground” on 6&7.
ive throughly checked every electrical harness and cleaned every connector, so I’m thinking this is an ECM issue.
My boats history is sketchy, so I think it could be corrosion inside of the ECM.
Does anyone know of any shops that repair PCM ECUs?

[jpwhit]

ECM failures are quite rare. Especially newer designs like the eControls ECM. They are extremely well sealed in potting so internal corrosion is unlikely. They are also not really repairable due to the potting. How well have you checked the contacts in the ECM connector on the wiring harness? If the socket had corrosion, then the plug will be suspect too, because it’s less well sealed than the socket. Unfortunately it’s harder to see the contacts than the pins in the socket. You often have to disassemble the connector to get a good look. This applies to all the key connectors. Such as the coils, injectors, and engine fuse / power box.

Can you give more details about why the boat has a sketchy history? Did it take on a lot of water? Fresh or Salt? Depending on what actually happened it can change how best to proceed. A lot of shops and people won’t take on a boat with certain types of water exposure because it can be so difficult to isolate and fix all the gremlins. For example if a boat has taken on enough salt water to reach the wiring harnesses, I’d recommend actually replacing all the harnesses. It costly and extremely time consuming, but it can be the only way to make the boat reliable over the long run.

For the particular problem with the codes you’re getting now, I would watch a lot of key signals with a digital storage oscilloscope and other electronic test equipment. But that’s an extreme way to diagnose the issue but less time consuming than other methods if you have the equipment and experience using it.