Cylinder inactivation codes?

Hello, are you getting cylinder misfire codes with MDS codes? The multi displacement system has 4 solenoids under the intake manifold on this model, they are power side switched components, so the ECM provides power to activate the solenoids. So, the question is the engine running on 4 cylinders or are you just getting codes for MDS circuits? What exact code numbers are you getting? Since the solenoids are power fed on individual wires and share a ground, the ECM might be monitoring either current flow or voltage and running some self-test and not seeing what it's supposed to see. I'll post the wiring diagrams for the solenoids.

Since it sounds like you're having codes for all four cylinders, I would say most likely this is a Ground issue. It's unlikely that all four wires coming from the ECM are having an issue unless they share a connector which has a problem. If the vehicle is running okay on all eight cylinders, then it sounds like the system is failing some self-test of those circuits. I'm looking on the OEM diagrams to see if there are any shared connectors anywhere.

Okay, is this a v8 or straight8? So far on the OEM diagrams its only showing on the srt8 engine, but I'll keep looking. And it looks like all four control solenoid wires and the one ground all share a connector. Cylinder 4 and 1 also share a connector further down towards the ECM. But C101 has the five wires we need to check. And are the codes setting at just key on engine off? You said they come back right away,

It's odd because service info is saying these codes set when transitioning from 8 to 4 cylinders.

I think it's a wiring issue as well. I'm trying to locate this C101 connector. See if you can locate this ground G102 (third diagram). The c101 connector is just the five wires for the solenoids.
The fourth diagram is the OEM with the connectors and splices we need to be concerned with. S115 s136 and connector c101
The fifth diagram shows s115 (splice) that's on the ground side, so anything on the ground side is of concern because it will cause all four solenoids or circuits to fail any self-tests.

Ok the seventh diagram is c101 on the driver side rear of the engine, that's the connector with all five of the wires for the MDS solenoids. The Black wire with a Brown stripe is the ground. It should have continuity to ground even with the key off.

But after the c101 connector the wire runs to the c100 connector then finally to its ground location g102, they have it running through multiple connectors for some reason. But it's a black/brown wire the whole way.

I know I keep adding things here, but the 10th diagram is a quick ground test at any of the connectors with a test light hooked to battery positive. Since this wire is always grounded it should light the test light with the key off.

Were you having these issues before the battery disconnect?

Were you able to find the c101 connector in the seventh diagram on the driver side rear of the engine with those five wires and colors? Usually, they are in that valley under the intake. What's this connector to the right in the picture, is that a 5-wire connector? This is the Ford OEM diagram for your vehicle, and the ECM is not going to throw codes out for a system it doesn't have. It's there, but I would concentrate on the wiring harness more than the solenoids. I don't think all four solenoids failed at once, a bad ground is really the only thing that would set all four circuit codes. Unless it's an ECM fault. Here are some possibilities, but this is only for one of the solenoids, so it can't be all of these causes.

I see someone pulled the system; I can understand doing that. So, the question is now, did they update the ECM after removing the system. And if so, it's not a normal ECM update. My guess would be that the battery disconnect may have reset the keep alive memory or erased whatever they used to update the ECM to keep it from setting trouble codes. I'll look into the removal techniques.

Okay well, I took a look at one of the kits that is used to delete the MDS system. It has quite a lot of hardware and the kits also come with a software tuner for the ECM to keep the light out. So, there's no telling what kit they used. But the kit replaces the cam, lifters, and a few gaskets back to stock items. I would think that the software changeover would stick, but I guess not. It may just be an option in the ECM and it reset. You can get ahold of this company if you want to try to get just the software section of the kit, it depends on your emissions testing in your area. Here if the check engine light is on it will not pass the inspection, but every state is different. Here's a video link to the company. Sorry we couldn't be more help. Tuner kits are just something we really don't deal with or have information on.

https://www.youtube.com/watch?v=Jg42nnWwpow

If the check engine light wasn't on before all this, they must have used some tuner software though to keep the light out. The caps in the kit also look like cheap caps for solenoid holes. I'm not sure if you pulled those codes using just the obd 2 global side of the scan tool but try going in on the manufacturers side and see if there are any special functions to disable the system that way. I've noticed with some recent updates to one of my Autel scan tools, there were some added special function tests and bidirectional controls that this scan tool did not come with, which I thought was really great. But you can also at least see what the ECM is doing under live data. There should be data PIDS for the BDS. If you search YouTube there was also a trick for temporarily disabling the system, although I don't know if that would keep the light out.

I'm going to email Melling and see what it takes to get their software. Or if there is some other way to update the ECM. Can't hurt to ask.
Will you fail inspection in your state with the check engine light on?