Hi great members,

I need your brains here so much. I have a 2016 GTS with only 3900 miles. Car currently has a check engine light, and I was able to pull out the code from my oem scanner with a remedy from Xentry as well. Took the car to a dealer to have them working on the issue with my diagnosis report that they agreed. Car is a CPO still; it drives fine under normal condition but will become misfire for a hard acceleration in S+ and Race mode. Shut the car off and no misfiring under idling. Which is so weird. Anyway, the car is at the dealer, they did a smoke test based on what AMG recommended and found a very minor leak at the connection between the turbo and down pipe. They want $1500 for that clamp which is a joke, so I told them let me buy new updated clamp and repair it myself. The advisor is cool with that and told me to bring the car once it’s done. My question to all is…I don’t think it’s the leak that causes the misfire, the software in my car is up to date so they can’t update it anymore per AMG’s protocol. Have anyone dealt with this code before and what was the fix in your case? I’m very handy, if needed I can do the spark plug too but gathering thoughts is essential so here I am.

The code is P030685




Thanks all

 

I had CEL P0301 on Cylinder 1. Apparently this is a known issue on the GT's, when I got the paperwork back it said the following; P030185, P030022. PER TIP DOC# GI54.21-P-061775, Software update and scn coding on engine module, power traiasn moudule and trany module due to software issue.

After the update I put on 5,000KM and never even seen a pending misfire code when randomly scanning.

Also worth noting my SA said it it ever comes back even outside warranty they will change the spark plugs for free under some "Critical Failure." Im leaning towards it being BS.

 

Interesting. So that clamp isn't part of the CPO? 1500 for it seems excessive.

 

thank you. I thought so too, but they keep saying my software is up to date.

 

Hello, Khoi,

Just a first question. Do you actually "feel" a misfire on two cylinders when in the high RPM range? If you actually have misfires on two cylinders on a V8, especially at higher RPM, it will be very noticeable. About the same feeling as hitting the Rev limiter.

The chronic issue with these two fantom misfires (cyls #1 and #6 which are two consecutive cylinders in the firing order) is really that the software algorithm used to define an amplitude range around the CPS signal output is too tight. The SW update relaxed that so the ECU should now need a broader out of range signal to actually ID a misfire. Or, in other words, a real misfire on these two cylinders would create a much more significant change in amplitude at consecutive places coming out of the CPS signal.

Also, it is remotely possible the exhaust leak in front of the O2 sensor on one bank is contributing to the misfire IDs. First and foremost, the SW update should correct this, but the contribution of the O2 sensor sensing too much unburned fuel might be part of the total algorithm used to ID misfires.

Hope you continue to update here after you correct the leaking exhaust.

All the Best,

Acta

 

hi Acta,

thanks for a promted and detailed response. Yes, the misfire is noticeable and CEL is flashing when I have my foot on the gas going to half or full throttle. It happens instantly, won’t happen when I stay and apply pressure off my foot on gas pedal constantly. I will update my post once I receive further instructions from AMG

 

Ok. then with a genuine misfire, the Xentry notice really isn't applying then and probably will need to look at an old fashioned misfire diagnosis. If AMG is evaluating it for you it will be interesting to see what they conclude, as the second half of the xentry report does just that - chases all the possibilities for a real misfire to ensure it was only SW.

Let's see what they say. I'll be particularly interested in their findings and hope you share it.

All the Best!

 

Hi Again Khoi,

Rethinking this a little bit more since there is a high coincidence the misfire of Cyls 1 and 6 continue to repeat and they are located on either side of the timing tooth on the reluctor, and with the RPMs in the PE range, fueling is going to be very rich. Throw in the loose/leaking exhaust clamp which could cause dozens of misfires, it might put the car in a lifesaving limp mode. So, I'm back with this is a possible chronic issue of SW too tightly wound, and even corrected is not enough with an extraneous impact such as a rich O2 sensor that would be signaling misfires. If this is the case, there might not be actual misfires (false misfires), just the EMS converting what it thinks it's seeing as dozens of misfires maybe hundreds into a catastrophic shutdown (limp mode) that is now feeling like misfires.

These are simplistic GENERIC examples and do not represent the actual firing order of the 4L platform:

A 58 tooth reluctor that produces a waveform and the gap represents an actual misfire. The gap occurs BC the crankshaft actually loses momentum in comparison to the torque supplied to the CS by all the other cylinders. On a V8 4 cycle engine there is a boost of rotational torque supplied to the CS every 90* of rotation.


Looking at an oscilloscope output - Every change in speed resulting in a decrease (As), is a piston on its compression stroke. Every reverse direction in speed (of the CS) resulting in an increase (Bs) is a piston on its power stroke. When a cylinder misfires, the loss of momentum on the power stroke results in a dramatic slowdown of the CS (Cs).



Now all the EMS needs is the timing tooth on the reluctor and the firing order and the numbered pistons can now be assigned and the misfire identified.






Again, in your particular case, the two cylinders that are misfiring are one and six, the first and last cylinders in the firing order on the 4.0L that surround the timing tooth, so there is something too "tightly wound" in the SW algorithm that defines upper and lower timing (time) ranges, thus the SW fix is to relax the limits and eliminate false misfires. But, with your SW already fixed, the leak at the clamp is still a possibility throwing more false info at the EMS.

 

hi Acta,

thanks again for such informative comment. To be clear, mine is firing on cylinder 1 only. I did the smoke test myself after they claimed the clamp was lose and asked me to pay $1500 to re-situate, retorque and install new clamp at the turbo and downpipe. I did multiple smoke tests and did not see a leak like they stated. I will take the car back to the dealer for further investigation.

 

I ended up doing the work myself. No new parts, just retightened the bolts and did the smoke test myself. I recorded a few videos, no smokes coming out off the connection downpipe and turbo. Used videos as a proof that it wasn’t the issued cashing misfire. Brought it back to the dealer, and now they have the car for further investigation. I highly doubt that they know what’s going on as well; according to the Tech, AMG sent him 4 pages of steps to follow. He believes the next step is to reset/adaptation with a test ride.

 

Very interested to hear the findings. Hope you report back.

 

Hello, I had a P30885. Symptoms was misfiring at idle. Did not notice on acceleration…Ignition coil and spark plugs replacement on cylinder 7/8.- Fixed.

FYI there were many faulty ignition coils on 2015/16 cars. There is a bulletin out there somewhere.

Hope this helps. GL.

 

I thank you so much. I found the bulletin. Will bring it to the dealer tomorrow.

 

Hi Acta,
Find attached. It's leading me to plug and coil.

 

You can confirm yourself if the coil is bad by switching a 'good' cylinder coil with a 'bad' cylinder coil. If the problem moves along it is likely coil. (Reset the CEL before the move).

 

Took the car to a different dealer, provided and worked with them on the fix. It was bad ignition coil.