Hello, my name is Sean and I live near Detroit Michigan. In my town there is barely any G or Z cars so it is really hard get help when I get any problem on the car. If you are in Michigan and know any shop who knows G35 well, please let me know. Also I don’t have much knowledge about car’s mechanism so please be mindful on my explanation.

I have 2003 G35 coupe 6sp and recently I am suffering a mysterious and stressful problem with my G from last 3 months. It’s been 4 years since I bought a used one and I took a good care of it ever since. It currently has 125,000 miles and I drove it from 80,000 miles.

Before I begin my story(very long), I would like to summarize the problems I currently have:
-Engine stalls on start up. I can keep it going by pressing a gas pedal, but the idle is unstable and can immediately get into a “Limp Mode” (with VDC,SLIP, Engine Service Soon Light on) with 1000rpm limit, 10 MPH speed limit

-Also I get 7 different OBD code when I scan

-Possible electrical problem but have a no ideas. No mechanics so far found out the exact problems. Replaced TB and MAF sensor did not work so far. Also I still get a MAF sensor code even after I replaced it.

To begin with, I want to mention my previous repair history which I think might affect to the current situation.

On last November, my car’s audio and climate control starts to disable. Sometimes it works, but sometimes the entire control is lost after few sec~min of vehicle start up. When controls are lost, I get a full blast of the air from the vent (although my climate system was off, it automatically starts) with the last preset temperature I had. But I still had audio sound and control from the steering wheel. Just no display and control from the center stack.

Other function was normal except the audio and climate control. Navi worked fine as well. I kept drove it.

On last December 27, after 100 miles of driving (I was in Canada), the car suddenly got into a limp mode when I was making a right turn. It was pretty cold day and I went for sking so the temperature was fair low (10 F or something) I had a climate and audio control alive on the center stack that day (some days it worked through entire driving, sometimes it just dead on the start-up). I stopped a car and turned it on again, the Limp mode was still engaged. I did it few times and finally the limp mode was gone, but the Engine service soon light came on and stayed.

Early January, I replaced the audio unit purchased from Infiniti dealership. It was installed by a local shop that specializes in Nissan and Infiniti (In Toronto, Canada) I also told them that I went to a limp mode once and they did OBD scan and told me the code is from the knock sensor. They just told me to drive more and see if it comes on again. They erased the code. They also noticed that I have a ticking sound from the engine and told me it might cause knock sensor to pop up the SES light.
In mid-January, One day the limp mode is on again after I exit from the highway and drive on the local road (About 30Mph). I pulled the car and started up again, the limp mode is gone and SES light is on again. Went to the local shop and pulled a scan code. They told me I have a numbers of code, just erased the code and did not do anything.

About a week later----------------------serious stuff begins
One day, I drove car for 30 miles and decided to change my air filter and put some addictive to my engine oil. I Went to Autozone and got a new 3” cone filter for my Injen Short Ram Intake. I changed filter and put an addictive. Car started up fine and I drove for another 30 miles on highway. After few hours, I started car and it went stall right away with the limp mode engaged. I tried to start up few times with pressing pedal, and it started but limp mode was on. I turned off and on but the limp mode is still on. The day was very cold (0 F) so I keep the car running about 30 min with the limp mode on. Suddenly some weird noise is heard so I went out, the car start to throw out coolant from the reservoir. Coolant temp was normal and there was no steam when I open the hood. It didn’t throw out a lot, but some coolants were spilled. I got scared and called a tow truck to my local shop that I went a week before.

They tried to start up the car normally. So cleaned throttle body and MAF sensor and so on, but did not solve the startup problem. ECU reset is tried but nothing happened (Limp mode still on) They said the fuel system is fine so they said I might have a bad TB or MAF. So I replaced to brand new OEM TB and nothing got better. So I replaced MAF Sensor, but still the same. The car is in a limp mode all the time so they told me they could not perform re learning stuff on TB and MAF sensor. The mechanic said he checked everything (wire,fuse,relay etc) he could possibly do. I also changed to new engine oil (Mobile 1 full synth extended performance 5W-30)

So I ended up with spending $700 for new TB and MAF sensor and the car stayed a whole week at the shop. Nothing got better so I towed it to the Infiniti dealership.

Dealership did a diagnostic and pulled a scan code. However, they told me that they need more time to look at the wires and stuff to find out the exact problem. They told me it’s a $600 to just find out the problem so I said no thanks. But I got OBD codes and mechanic’s opinion on the car’s situation. So here are my OBD codes:

P0550 Power Steering Pressure Sensor Circuit Malfunction
P0605 ECM Fault
P0052 Air Fuel Ratio Sensor 1 Heater Bank 2 Control Circuit High
P0327 Knock Sensor Circuit Low Input Bank 1
P0102 Mass or Volume Air Flow Circuit Low Input
P0113 Intake Air Temperature Sensor Circuit High
P0183 Fuel Tank Temperature Sensor Circuit High Input

Strange thing is that although I have a new TB and MAF sensor, the code is still up for MAF (P0102). Power steering is perfectly fine but there is a code for it. So I have no clue with this.

The dealer said I may need to replace ECM. Knock sensors, o2 sensor and fuel tank temp sensor.

Also they noticed for my ticking sound from the engine, said engine lifter noise is from the right side silicone, need to replace intake manifold gaskets, valve cover gaskets and lifter buckets. However I don’t think this is related to other problem.

Yesterday, I towed my car back from the dealership and tried to start up the car. It started without being on a limp mode (but still SES on) so I drove for 30 miles. Car drives normally, no loss of power or anything

Today I start up the car and it is on stall right away, tried again and pressed gas pedal to keep it alive, but the limp mode is on. So I turned off and on again and the limp mode is gone. Drove for 30 second and the limp mode came back, so I parked it and turned it off.

----------weird-------When I turn it on again, the speed and rpm needles were not moving at all but the car started. Background light was on, limp mode lights were gone, but the oil pressure warning light was on with it (WTF?) so I turned it off and on again, the needles were moving normally and the car started without being on a limp mode. I got scared so did not do anything else after this.

And here is my personal questions:
-Is there any possibility that my current situation is related to my previous audio unit problem? (circuit board thing which I replaced)
-A dealer wrote that my car’s battery is failed on the capacity test. Is that meaning my battery is done? And might cause this problem? It’s been 2 years since I replaced it. I don’t see any signs of short battery yet.
-Maybe bad ECM caused all the problems?

I don’t really know what to do now. The car is sitting on my house parking lot and I don’t know where to go for real diagnostic and professional repair. So I am desperately asking for any suggestion and possible cause. Thanks for reading such a long post and I am looking for any reply so please help me if you have any idea on my situation. I thank you in advance.
-Sean-

 

Do you smell strong gas odor when you pop the hood. If so it could be related to fuel pump problem or dirty/bad injectors. I understand they said fuel system is good. but did they just look at the Fuel Trim on the scanner thats not gunna tell you . You should pop off the rear seat and do a fuel pressure test ... Someone correct me if I am wrong but it should be 51psi @ idle. Just remember AIR FUEL SPARK... most everything else is traced to electrical short/sensor

 

to smell strong fuel for this engine would mean leaking injectors. leaking injectors are not common for stock but is common if you have upgraded brands like venom combined with high pressure walbro 255 fuel pump... an injector stuck open will put the car into limp mode as i have had that occur. your symptom seems to be a low voltage or overly high voltage condition. volt meter test the car to see its getting 13.6-14.4v, not less or higher while idling and revving. i've had this issue working on bmw and nissan with faulty alternators.

however, a faulty thermostat with bad o2 sensor also puts a car into limp mode. you mentioned coolant back pressure, this can occur from a blown head gasket, cracked head, or stuck closed thermostat.

replacing throttle body and mass is unnecessary as they both can be cleaned and relearn procedure performed.

 

to find good automotive shops to repair your car as your nearest auto parts store to recommend a shop. Trust me they will know