P3401 - But MDS is Disabled and all hardware Deleted

[PVelaIII]

This is most likely not a tune related issue however I would like some of your opinions on what I'm experiencing at the moment with the following.

Had a misfire/'dead' cylinder scenario show up two days ago. Been running perfect for the past two years, both as a daily drive and HPDE/Hot Lap Time Trial.

While coasting to a stop from the highway exit, I noticed a bit of hesitation/stumble with the engine. While sitting at the light it was obvious that a cylinder was misfiring/dead. Light load acceleration and it just stumbled as you would expect. But as you get moving it clears itself up and moves right along as usual and misfire disappears.

So, I hooked up that laptop once I got home and find the following: No Check Engine Light at any time, P3401 - Cylinder 1 Deactivation/Intake Valve Ctrl Circ/Open (Permanent)

The kicker...mds was deleted (hardware) and disabled (software) during a top end rebuild 2yrs ago due to the notorious failed lifter issue.

Has anyone experienced this before? It confuses me how P3401 would show up without any other symptoms. I pulled the spark plugs for cylinder 1 and they looked perfect but replaced them because we've all been bitten by a good-looking spark plug. The ecu is detecting an open circuit for MDS in Cylinder 1 and is disabling the ignition/spark plug.

Thoughts, ideas, suggestions before I go tearing through and inspecting the hardware, software, and wiring? I would really appreciate hearing from you all.

Everything looks good in the tune, MDS is of course disabled.


2014 Jeep Grand Cherokee SRT, 6.4L, MMX NSR-Stage 3 Camshaft kit with MDS Delete, Fuel Injector Clinic 525CC Injectors, 185 Degree Thermostat, MMX Ported Throttle Body. MMX Custom Tune.

[SleepyRT]

This is most likely not a tune related issue however I would like some of your opinions on what I'm experiencing at the moment with the following.

Had a misfire/'dead' cylinder scenario show up two days ago. Been running perfect for the past two years, both as a daily drive and HPDE/Hot Lap Time Trial.

While coasting to a stop from the highway exit, I noticed a bit of hesitation/stumble with the engine. While sitting at the light it was obvious that a cylinder was misfiring/dead. Light load acceleration and it just stumbled as you would expect. But as you get moving it clears itself up and moves right along as usual and misfire disappears.

So, I hooked up that laptop once I got home and find the following: No Check Engine Light at any time, P3401 - Cylinder 1 Deactivation/Intake Valve Ctrl Circ/Open (Permanent)

The kicker...mds was deleted (hardware) and disabled (software) during a top end rebuild 2yrs ago due to the notorious failed lifter issue.

Has anyone experienced this before? It confuses me how P3401 would show up without any other symptoms. I pulled the spark plugs for cylinder 1 and they looked perfect but replaced them because we've all been bitten by a good-looking spark plug. The ecu is detecting an open circuit for MDS in Cylinder 1 and is disabling the ignition/spark plug.

Thoughts, ideas, suggestions before I go tearing through and inspecting the hardware, software, and wiring? I would really appreciate hearing from you all.

Everything looks good in the tune, MDS is of course disabled.


2014 Jeep Grand Cherokee SRT, 6.4L, MMX NSR-Stage 3 Camshaft kit with MDS Delete, Fuel Injector Clinic 525CC Injectors, 185 Degree Thermostat, MMX Ported Throttle Body. MMX Custom Tune.

Given that MDS is turned off, the other condition that will throw this code is low oil pressure. Even with MDS off the ECU will still try to turn MDS off (go open) if oil pressure drops.

Read more at: https://www.obd-codes.com/p3401
Copyright OBD-Codes.com

[PVelaIII]

This is most likely not a tune related issue however I would like some of your opinions on what I'm experiencing at the moment with the following.

Had a misfire/'dead' cylinder scenario show up two days ago. Been running perfect for the past two years, both as a daily drive and HPDE/Hot Lap Time Trial.

While coasting to a stop from the highway exit, I noticed a bit of hesitation/stumble with the engine. While sitting at the light it was obvious that a cylinder was misfiring/dead. Light load acceleration and it just stumbled as you would expect. But as you get moving it clears itself up and moves right along as usual and misfire disappears.

So, I hooked up that laptop once I got home and find the following: No Check Engine Light at any time, P3401 - Cylinder 1 Deactivation/Intake Valve Ctrl Circ/Open (Permanent)

The kicker...mds was deleted (hardware) and disabled (software) during a top end rebuild 2yrs ago due to the notorious failed lifter issue.

Has anyone experienced this before? It confuses me how P3401 would show up without any other symptoms. I pulled the spark plugs for cylinder 1 and they looked perfect but replaced them because we've all been bitten by a good-looking spark plug. The ecu is detecting an open circuit for MDS in Cylinder 1 and is disabling the ignition/spark plug.

Thoughts, ideas, suggestions before I go tearing through and inspecting the hardware, software, and wiring? I would really appreciate hearing from you all.

Everything looks good in the tune, MDS is of course disabled.


2014 Jeep Grand Cherokee SRT, 6.4L, MMX NSR-Stage 3 Camshaft kit with MDS Delete, Fuel Injector Clinic 525CC Injectors, 185 Degree Thermostat, MMX Ported Throttle Body. MMX Custom Tune.

Thank you for the direction and I think you are on to something. This started right after an oil change with Mobil 1. Changing it back to Penzoil ASAP to see what it does. I've read of others having issues with MDS when switching to Mobil1