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Infiniti G37 shuddering, bucking above 2500 rpm, limp mode issue 6MT
I own a pretty low-mileage (44k) 2009 G37 6MT and I've never had any problems with the car. Recently on the way home from a car wash the car began to shudder and buck when I accelerated past 2500 rpm and the Check Engine Light (CEL) came on. This happened in any gear. If I changed gears quickly and kept from hitting 2500 rpm I could avoid it but eventually you're going to need to go 2500 rpm and something was clearly wrong.
So I parked the car at home and started searching Infiniti forums for people who may have had the same issue. I didn't find a whole lot, but I did find a couple G35 drivers who described the same thing; "bucking" and shuddering over 2500 rpm. The issue that kept being suggested was "limp mode"; basically that when the car's computer determines that there is a problem it limits the vehicle's acceleration to under 2500 rpm. I read a number of suggestions as to what may cause this but one of them caught my eye, which was that when certain sensors get wet this can trick the car into limp mode. Seeing as how I had just come from a car wash when this happened I had a hunch this could be the case.
Ok wait this gets better, sorry I know this is a long-winded description but keep reading. So I was really only trying to look this stuff up to get a rough idea of the problem so that I'm armed with a little knowledge to avoid getting [non-permissible content removed]-raped by some mechanic before I got this checked out. But I was reading all these forums and more than one person suggested doing an "ECU reset" to see if that worked before throwing a lot of time or money at the issue. I really had no idea what that was or how to do that but I decided to give it a try, since it seemed to be implied that anyone could do this. So after doing a little searching I found this video on youtube:
Now I'm not pretending to be a mechanic or car expert here so excuse me if I've used any incorrect terminology, etc., but if you follow what is done in the short video you can definitely reset your ECU yourself. There are also a couple forums with written instructions on how to do this if you just google "G37 ECU reset". As you can see it is a little tricky and you have to have perfect timing (press start twice, wait 3 seconds, press accelerator pedal 5 times quickly, wait 10 seconds, wait for the CEL to start blinking, etc.), it took me about 5 tries before it worked. But guess what, it worked! After the reset the CEL was no longer on, and when I took the car out, sure enough, the problem had disappeared. No shuddering, bucking, stalling or any problem going over 2500 rpm.
It seems that what probably happened is a sensor got wet in the car wash, which caused the car's computer to trigger limp mode. Resetting the ECU cleared the issue. I don't know for sure that the problem is "fixed" or whether or not it will happen again, but at least I know what I can do if it does. Definitely try this if you're having the same issue!