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Discussion Starter · #1 ·
I have a 2017 Infiniti Q50 Premium I Have Megan downpipes, Rev9 exhaust, AMS HX, AMS flex fuel kit, AMS intakes, ADD W1 oil catch can, HKS BOV's. The car is tuned on ECUTEK and is pushing around 415hp/465tq.

Now for the problem, so I wanted to install upper downpipes without altering the tune or anything. Just slap them on and go. It took me 10 hours and a sore body but i got them on their. That was my first problem, as soon as I started the car the car took 5-7 seconds to start up. (I had disconnected the battery and disconnected the ecu cables by the battery so I could get to some screws.) I assumed it took this long because the fuel pressure had dropped and was normalizing. The car dropped in idle down to about 500 then jumped back up to 670 and then proceeded to start cycling like in a rhythm going from 600-1100rpms. It sounded really rough, smelled terrible (obviously because no cats:). and just sounded like it wanted to die.

I then check for codes and had 15 or so pop up everything from the ECU to oil pressure and so on, any way's after trying to troubleshoot I gave up and put the primary cats back in. This is my real problem. After putting them back in and starting the car, it started up still took it 5-7 seconds but then started to idle fine. But I still had 2 codes left 1 was a U0100 and the other P0390 code. U0100 code said, "Lost communication With ECM/PCM "A"" and also mentioned that it was a Transmission code. P0390 code said," Camshaft Position Sensor" and mentioned that it was an engine code. On the dash the check engine light isn't lit up but the Traction control or VDC light stays on no matter what I do. The engine currently seems to run fine with a very slight off sound to it.

The transmission is a whole other story. The tranny goes into gear but jerks hard when going through gears and will climb up to 3000-3500rpm per gear, it wont try to find a cruising gear. The throttle is very, very heavy I nearly have to push it all the way down to move it, and when it switches gear the whole car shudders or shakes. I tried putting it into sport mode and manually shifting but it slammed and jerked into 4th so hard and badly I could hear the metallic clunk in the cabin, so I cruised in neutral till I got back home (finishing a test drive was almost home). When I got home their was a strange smell coming from the engine bay almost like the coolant but different and from behind the engine so I'm thinking maybe the clutch packs? I have set up an appointment with a local shop to see if they can find any issue, I'm gonna try my tuner and as a last resort ill take it to the dealer since it is modified and has an aftermarket tune on it. But what do you think guys and gals did I throw my car into limp mode?

I tried to clear the codes but they come back, I tried to "reset" the ECU by disconnecting the battery codes are still up, I checked all the fuses to see if I blew anything but nothing.

At this point I'm pretty desperate, and any insight and help would be awesome:)
 

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I would trace the P0390 code for the camshaft sensor. Somehow you either disconnected or damaged the connector for what appears is the camshaft sensor. Intermittent or no camshaft position sensed would put the car in limp mode, and have a follow-on effect of the transmission behavior you witnessed.
 

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P0390 isn't a transmission DTC. It's indicating a problem with the bank 2 (driver's side) exhaust camshaft position sensor. The sensor signal is not inputted, inappropriate or partially missing going to the ECM for approximately 1 consecutive second or more during engine run or start. The car goes into device fix mode where the electric intake valve timing control motor and the exhaust valve timing control solenoid valve are fixed in the reference position. I think that's what you are experiencing as "limp mode".

It could be a bad exhaust camshaft position sensor or a dirty or damaged exhaust camshaft position sensor rotor. However, given what you were doing, I'd suspect as IridiumRS400 does that you have somehow interrupted the sensor's signal to the ECM by either an open or shorted circuit.
 

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Discussion Starter · #4 ·
I’ll check it out when I get home from work, but would their be a way to verify if it’s the camshaft position sensor doing this, using a multimeter or something like that? I am just dumbfounded as to how this sensor could through the car off like this, so badly!
 

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I have a 2017 Infiniti Q50 Premium I Have Megan downpipes, Rev9 exhaust, AMS HX, AMS flex fuel kit, AMS intakes, ADD W1 oil catch can, HKS BOV's. The car is tuned on ECUTEK and is pushing around 415hp/465tq.

Now for the problem, so I wanted to install upper downpipes without altering the tune or anything. Just slap them on and go. It took me 10 hours and a sore body but i got them on their. That was my first problem, as soon as I started the car the car took 5-7 seconds to start up. (I had disconnected the battery and disconnected the ecu cables by the battery so I could get to some screws.) I assumed it took this long because the fuel pressure had dropped and was normalizing. The car dropped in idle down to about 500 then jumped back up to 670 and then proceeded to start cycling like in a rhythm going from 600-1100rpms. It sounded really rough, smelled terrible (obviously because no cats:). and just sounded like it wanted to die.

I then check for codes and had 15 or so pop up everything from the ECU to oil pressure and so on, any way's after trying to troubleshoot I gave up and put the primary cats back in. This is my real problem. After putting them back in and starting the car, it started up still took it 5-7 seconds but then started to idle fine. But I still had 2 codes left 1 was a U0100 and the other P0390 code. U0100 code said, "Lost communication With ECM/PCM "A"" and also mentioned that it was a Transmission code. P0390 code said," Camshaft Position Sensor" and mentioned that it was an engine code. On the dash the check engine light isn't lit up but the Traction control or VDC light stays on no matter what I do. The engine currently seems to run fine with a very slight off sound to it.

The transmission is a whole other story. The tranny goes into gear but jerks hard when going through gears and will climb up to 3000-3500rpm per gear, it wont try to find a cruising gear. The throttle is very, very heavy I nearly have to push it all the way down to move it, and when it switches gear the whole car shudders or shakes. I tried putting it into sport mode and manually shifting but it slammed and jerked into 4th so hard and badly I could hear the metallic clunk in the cabin, so I cruised in neutral till I got back home (finishing a test drive was almost home). When I got home their was a strange smell coming from the engine bay almost like the coolant but different and from behind the engine so I'm thinking maybe the clutch packs? I have set up an appointment with a local shop to see if they can find any issue, I'm gonna try my tuner and as a last resort ill take it to the dealer since it is modified and has an aftermarket tune on it. But what do you think guys and gals did I throw my car into limp mode?

I tried to clear the codes but they come back, I tried to "reset" the ECU by disconnecting the battery codes are still up, I checked all the fuses to see if I blew anything but nothing.

At this point I'm pretty desperate, and any insight and help would be awesome:)
Надеюсь что ничего плохого случилось...
 

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(I had disconnected the battery and disconnected the ecu cables by the battery so I could get to some screws.) I assumed it took this long because the fuel pressure had dropped and was normalizing.
You should remove and inspect this connector(s) to see if its fully-engaged or a pin got bent over when you re-connected it. My guess is the camshaft sensor input/output goes through this connector, and is not making full contact.

I wouldn't go chasing the camshaft sensor itself - not until you verify every electrical connection that was disturbed when you R&R'd the primary converters is verified to be a good connection.
 

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Discussion Starter · #8 ·
I checked the cables that I unhooked and inspected them for any bent, missing or broken pins and everything is spotless and clean. Codes still show up and car behaves in the same way.😞 I am wondering now if I might have frayed cut or done something to the wiring down below. Removing and reinstalling that drivers side cat was tricky because the steering rack is in the way. 🤔
 

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Sounds like you inadvertently pulled on a wiring harness which probably disconnected some wiring. Tight quarters fiddling around there. I hate electrical problems. Good luck with it.
 

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Discussion Starter · #10 ·
Sounds like you inadvertently pulled on a wiring harness which probably disconnected some wiring. Tight quarters fiddling around there. I hate electrical problems. Good luck with it.
P0390 isn't a transmission DTC. It's indicating a problem with the bank 2 (driver's side) exhaust camshaft position sensor. The sensor signal is not inputted, inappropriate or partially missing going to the ECM for approximately 1 consecutive second or more during engine run or start. The car goes into device fix mode where the electric intake valve timing control motor and the exhaust valve timing control solenoid valve are fixed in the reference position. I think that's what you are experiencing as "limp mode".

It could be a bad exhaust camshaft position sensor or a dirty or damaged exhaust camshaft position sensor rotor. However, given what you were doing, I'd suspect as IridiumRS400 does that you have somehow interrupted the sensor's signal to the ECM by either an open or shorted circuit.
so, I left the battery unplugged for about a day and a half. Plugged everything back in and started the car. It fired up but started doing its rythmic cycling again. When I checked for codes 9 of the 12 I had originally popped back up. At this point I’m at a loss cuase I doesn’t look like it’s 1 specific sensor but potentially is the ecu?
98019
 

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All of those DTCs are probably related to open or shorted connectors or harness wires. Most are probably triggered by the primary cause of your problem and would likely clear if you were to find the root cause and correct it. I think you should take the car in for further diagnostic testing to determine where the problem is.
 

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Discussion Starter · #12 ·
Thanks Avedis53, that’s what I’m gonna go ahead and do. I got the car scheduled for a full diagnostic at a local shop. Hopefully they can figure it out. I’m hoping that it’s not a damaged ecu or harness.😅
 

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Thanks Avedis53, that’s what I’m gonna go ahead and do. I got the car scheduled for a full diagnostic at a local shop. Hopefully they can figure it out. I’m hoping that it’s not a damaged ecu or harness.😅
Good luck!
 

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Discussion Starter · #14 ·
98031
BREAKING NEWS!!! So I went back in, in my depressed state and guess what! One of the ECU cables I disconnected from a previous flex fuel kit endeavor, looked like this; as you can see the grey one is flush but the yellow one has an entire bank that ispushed back all the way. I took it apart, pushed it back, connected it.

And with fingers crossed cleared the codes, started the car and boom engine light and transmission light gone all the codes disappeared except 1 U0100. Thank you guys so much for the help and encouragement!!! Also do you guys know if the remaining code can be cleared or if the dealer needs to clear it?
 

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And with fingers crossed cleared the codes, started the car and boom engine light and transmission light gone all the codes disappeared except 1 U0100. Thank you guys so much for the help and encouragement!!! Also do you guys know if the remaining code can be cleared or if the dealer needs to clear it?
If the car runs and drives, and no other codes pop up, it may a "soft" code. It's basically a code for the ECM & PCM Can-bus communication status (loss thereof).
 
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It could possibly clear after some drive time.
 
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